a metallic substance, formerly considered as one of the brittle metals; or, according to the distinction of the older chemists, a semi-metal or an imperfect metal, because it was found to be destitute of some of the properties of other metals which were considered as perfect. For an account of the properties and combinations of zinc, as they were then known, see CHEMISTRY Index; and for the history of its ores, see MINERALOGY Index.

But in the progress of chemical discovery it has been found that zinc is not a less perfect metal than others; for in the year 1805, it was announced that a patent was granted to Mefrs Hobson and Sylvester of Sheffield for a method of manufacturing zinc. From their discovery it appears, that zinc raised to a temperature of between 210° and 300° of Fahrenheit, is not only very malleable, but may be passed through rollers, or drawn into wire. After the metal has been treated in this manner, it does not return to its former brittleness, but continues soft, flexible, and extensible, and may be applied to many uses for which this metal was before thought unfit.

We must, however, notice, that a prior claim to the discovery of rendering zinc ductile and malleable, has been made by Mr Lowry, in favour of a Mr Sheffield of Somers-town. Twenty years before the time of Mefrs Hobson and Sylvester's patent being announced, Mr Sheffield, in making an assay of some blende, was impatient to examine the metal, struck an ingot for the purpose of breaking it while it was yet hot, but was much surprised to find that instead of being brittle, and breaking with the usual fracture of zinc, it was extremely tough, and when he succeeded in breaking it, after many bendings backward and forward, it exhibited a steel-grained fibrous texture. At first he doubted of the metal being zinc, but he repeated the experiment on what he knew to be pure metal, and obtained the same result; and from this he concluded that zinc at a certain temperature is equally malleable and ductile with other metals. This he found to be the case by drawing it into wire, and laminating it between rollers, by which he produced plates not exceeding the \( \frac{1}{100} \)th of an inch, and possessing the strength and tenacity of silver.

Since the time that our article CHEMISTRY was printed, the decomposition of potash, soda, the alkaline earths, and some other bodies which were formerly considered as simple, or were only conjectured from analogy to be compound, has been effected by Mr Davy; and as we were disposed to entertain hopes that something new might be added to the unexpected and brilliant discoveries of that celebrated chemist, we have deferred, till near the close of our work, giving any account of them. This is the reason that the fact was merely announced under the words POTASH and SODA, and a reference made to Galvanic TROUGH, under which it was intended to give a short description of the apparatus employed in the experiments which led to the discoveries alluded to. For the same reason we were induced to make a farther reference to this place, because zinc is one of the metallic substances usually employed in the construction of galvanic apparatus. We shall therefore here employ a few pages, 1st, In a description of the improvements which have been made in the construction of galvanic apparatus; and, 2d, We shall lay before our readers a view of the discoveries in galvanic electricity since the treatises on Chemistry and Galvanism in this work were printed.

Galvanic Apparatus.—A very considerable improvement has been made on the construction of galvanic batteries, by which they are rendered, not only more convenient and manageable, but far more powerful. Under the article Galvanism, we have described particularly the construction of the galvanic trough, and we have noticed that the folding of the plates of zinc and copper employed for this purpose was attended with considerable difficulty. In the new method of construction the plates are not folded together, but are merely connected by means of a metallic arc. In this way each pair of plates can be removed from the trough at pleasure, for the purpose of examining and cleaning them. The new apparatus is constructed precisely on the same principle as the couronne de Tafes, proposed by Volta, and described at p. 333 of Galvanism. The trough employed in this apparatus is prepared in the same way as when the plates of zinc and copper folded together were fixed in it by means of cement; but in place of the metallic plates, plates of glass, or some other non-conducting substance, are introduced and secured by cement, so that there shall be no communication between the different cells into which the liquid is introduced. The plates of zinc and copper connected by means of the metallic arc, at the distance of about half an inch, are placed in different cells, having a plate of glass between each pair of plates. Each cell then contains a plate of each of the metals, which are unconnected, excepting through the medium of the liquid which is to be the conductor of the electricity. It is scarcely necessary to mention, that the proper order of arrangement shall be observed, so that throughout the whole trough or battery there shall be a series of zinc, copper, and liquid.

Beside the convenience and simplicity of this mode of constructing galvanic troughs, it possesses this farther advantage of being more powerful, because instead of one surface of the plates, as in the former construction of this apparatus, both surfaces are exposed to the action of electricity, and therefore the power is greatly increased. A farther improvement, it is said, has been made in constructing batteries of this kind, which consists in employing troughs of Wedgwood's ware, with partitions of the same material, instead of wooden troughs with partitions of glass. This improvement was first suggested by Dr Babington.

The following is the account of the construction of galvanic apparatus, with the view of ascertaining in what way the greatest effect might be produced, with the least waste of power and expense. The experiments which we are now to mention were made by Mr Children*. For this purpose a battery was constructed on the new method, with plates of copper and zinc, connected by leaden straps, folded on the top of each pair of plates. Twenty pairs of plates were employed, and each plate was four feet high by two feet wide. The whole extent of surface exposed amounted to 92,160 square inches; the trough was made of wood, with wooden partitions, covered with cement, to resist the action of the acid employed. The battery was charged with a mixture of three parts of fuming nitrous, and one of sulphuric acid, diluted with thirty of water; the quantity employed was 120 gallons. With this apparatus the following experiments were made.

Exper. 1. Eighteen inches of platina wire, of one-thirtieth of an inch diameter were completely fused in about twenty seconds. Exper. 2. Three feet of the same wire were heated to a bright red, visible by strong day-light. Exper. 3. Four feet of the same wire were rendered very hot, but not perceptibly red by day-light. Exper. 4. Charcoal burnt with intense brilliancy. Exper. 5. Ten inches of iron-wire of \( \frac{7}{10} \)th of an inch diameter, were barely fused; three feet of the same wire were not ignited. Exper. 6. No effect was produced on imperfect conductors. Exper. 7. The gold-leaves of the electrometer were not affected. Exper. 8. When the cuticle was dry, no shock was given by the battery, and it was scarcely perceptible when the skin was wet.

To contrast the effects of this apparatus with another differing in the size and number of plates, the author employed 200 pairs of plates, each about two inches square, placed in half pint pots of common queen's ware. The same liquid was employed, with the addition of a fresh portion of sulphuric acid, in the proportion of about a quarter of a pint to a gallon. The experiments with this apparatus gave the following results:

Exper. 1. Potash and barytes were readily decomposed. Exper. 2. The metallization of ammonia was produced with great facility. Exper. 3. Charcoal was vividly ignited. Exper. 4. The gold leaves of the electrometer diverged considerably. Exper. 5. After the battery was in action three hours, it gave a vivid spark; at the end of 24 hours it metallized ammonia; at the end of 41 hours it was nearly exhausted. From the results of these experiments, Mr Children concludes, that the theory of the mode of action of the voltaic battery propounded by Mr Davy is confirmed, namely, that the intensity increases with the number, and the quantity with the extent of the series. This is proved by the effects produced on the platina and iron wires, in the 1st and 5th experiments with the large battery, as well as by the experiments on imperfect conductors in the small apparatus; for as the platina wire is a perfect conductor, and not liable to oxidation, it allows the electricities to be freely transmitted, and from the immense quantity given out from a surface of such extent, they evolve, on their mutual annihilation, heat sufficient to raise the temperature of the platina to the point of fusion. But a very small portion of the electricity passes through the iron wire, in consequence of its easy oxidation, and the thin coat of oxide formed on its surface. This arises from the low state of the intensity of the electricity, as appears also from its want of power on the gold leaves of the electrometer. From the same deficient intensity, the decomposition of barytes could not be effected by the large battery, and the same battery exhibited a very weak action on imperfect conductors; but the small battery exerted great power on that class of bodies, and decomposed them readily, although its surface was 30 times less than the surface of the great battery; but the num- ber of plates was nearly ten times greater. Another circumstance, of considerable importance in conducting experiments by means of the galvanic battery, is here noticed by the author; that the long continued action of the small battery was owing to the large capacity of the cells containing a proportional quantity of liquor. And beside this advantage he adds, that with very large combinations, a certain distance between each pair of plates is absolutely necessary to prevent spontaneous discharges, which are accompanied with vivid flashes of electric light. This happened to the author with a battery of 1250 four-inch plates, constructed according to the new method. Mr Children has constructed a battery of 20 pairs of fix feet high and 2½ broad, and with this battery he ignited 6 feet of platina wire.

From the experiments and observations, some of which we have detailed, and for others we refer to the paper itself, the author concludes with the following remarks: "The absolute effect of a voltaic apparatus seems to be in the compound ratio of the number and size of the plates. The intensity of the electricity being as the former, the quantity given out as the latter, consequently regard must be had, in its construction, to the purposes for which it is designed. For experiments on perfect conductors, very large plates are to be preferred, a small number of which will probably be sufficient; but where the resistance of imperfect conductors is to be overcome, the combination must be great, but the size of the plates may be small: but if quantity and intensity be both required, then a large number of large plates will be necessary. For general purposes, four inches square will be found to be the most convenient size*."

Discoveries in Galvanism.—At the close of the article GALVANISM, we noticed some experiments which were made about the beginning of the year 1805, which seemed to lead to the conclusion, that muriatic acid and soda were formed by means of galvanic electricity. In experiments on the decomposition of water, which was supposed to be in a state of the utmost purity, the appearance of muriatic acid and soda was adduced in support of this opinion. The accuracy of this conclusion, which seemed to be at variance with known facts, excited doubt, and probably led to the investigation which was undertaken by Mr Davy, and carried on with great ingenuity and address by the same philosopher, till it terminated in the brilliant discoveries, an account of which we are now to detail. Mr Davy's researches in galvanism, an account of which he laid before the Royal Society in a memoir entitled, On some Chemical Agencies of Electricity, may be considered as the first step in this train of investigation.

With the view of disproving the accuracy of the experiments in which the generation of acids and alkalies was supposed to have been effected by means of galvanic

Plate dxxxviii. fig. 1., Mr Davy employed agate cups, (fig. 1.), of a cylindrical form, and containing about one-fourth of a cubic inch each. The cups were boiled for some hours in distilled water, and a piece of white transparent amianthus, which had been treated in the same way, was made to connect them. They were then filled with distilled water, and exposed by means of two platina wires, to a current of electricity, from 150 pairs of plates of copper and zinc, four inches square. The liquid employed was a solution of alum. The action continued 48 hours, and the process was then examined. Paper tinged with litmus introduced into the tube containing the positive wire, was reddened; paper coloured by turmeric placed in the other tube, had its colour deepened; the acid matter produced a slight turbidity in a solution of nitrate of silver; the fluid from the negative tube retained the property of affecting the turmeric after being boiled, and indeed became more vivid as the quantity was diminished by evaporation. Carbonate of ammonia was added, and the whole being dried, and exposed to a strong heat, a minute quantity of white matter remained, which had all the properties of carbonate of soda.

The same experiment was repeated with glass tubes, and the result was, that the quantity of alkali obtained was 29 times greater, but no traces of muriatic acid could be perceived. Mr Davy suspecting that the agate might contain a minute portion of saline matter, repeated the experiment four times. The quantity of alkaline matter diminished in every operation, and in the last process, although the battery had been kept in great activity for three days, the fluid possessed in a slight degree only the power of acting on paper tinged with turmeric; but its alkaline property was very sensible to litmus paper slightly reddened. The acid matter in the other tube was abundant; it had a sour taste, and produced no effect on solution of muriate of barytes, but left a black stain from a drop on a polished plate of silver. Thus it appeared to be extremely diluted nitrous acid.

For the purpose of making the experiment with greater accuracy, two hollow cones of pure gold (fig. 2.) Fig. 2. were employed, each containing about 25 grains of water. They were filled with distilled water, connected by moistened amianthus, as before, and exposed to the action of a battery of 100 pairs of plates of six inches square. The liquid used was a solution of alum, and diluted sulphuric acid. In ten minutes the water in the negative tube changed litmus paper to a slight blue, and the water in the positive tube produced a red tint. The process having continued for 14 hours, the acid was found to increase in quantity during the whole time, but the alkaline fluid in the other tube did not affect the tests more than in the first trial. The acid seemed to be the pure nitrous, with an excess of nitrous gas. The experiment was repeated, and the process carried on for three days, and similar results were obtained. From these experiments it was concluded, that the distilled water contained a minute portion of saline matter, but to minute indeed, that it was insensible to the most delicate chemical tests. This appeared to be the case by evaporating a quantity of the distilled water that was used, very slowly, at a heat below 140° Fahrenheit, in a silver still. A quantity of solid matter equal to seven-tenths of a grain, of a saline but metallic taste, was obtained. It seemed to be a mixture of nitrate of soda and nitrate of lead. Mr Davy then employed some of the water collected in the second process of slow distillation, in another experiment with the gold tubes and connecting amianthus. At the end of two hours the water in the negative tube had no effect on turmeric paper; litmus, it could just be perceived, was changed; but by heating the water strongly for two or three minutes, it was deprived even of this power, and from this he supposes that it was owing to a small quantity of ammonia. A similar experiment was made with a portion of the same water in the agate tubes, and precisely the same results were obtained. From these experiments Mr Davy fairly concludes, that the fixed alkali is not generated during the process, but merely evolved, either from the solid materials employed, or some saline matter in the water.

Many experiments were made in vessels composed of different substances, with the water procured by flow distillation; and in almost every instance some fixed alkali appeared. When tubes of wax were employed, the alkaline matter was a mixture of soda and potash, and the acid matter, a mixture of sulphuric, muriatic, and nitric acids. A tube of resin afforded alkaline matter, which was principally potash. A cube of Carrara marble of about an inch, having an aperture in its centre, was placed in a platina crucible, which was filled as high as the upper surface of the cube, with the purified water. The aperture was filled with the same liquid, and the crucible was positively electrified by a powerful battery, and the negatively electrified wire introduced into the aperture. Fixed alkali and lime were obtained in this experiment; the quantity of alkali diminishing as the experiment was repeated, and after 11 processes, each continued for two or three hours, disappeared altogether. The quantity of lime-water obtained was uniform.

When 500 grains of this marble were analyzed, they afforded about three-fourths of a grain of fixed saline matter, having soda for its base. Suspecting that the Carrara marble might have been recently exposed to sea water, Mr Davy subjected to a similar experiment, a piece of granular marble from the mountains of Donnegal, and by means of negative electricity he obtained fixed alkali. Argillaceous schistus from Cornwall gave the same result, and serpentine and gray wacken both afforded soda.

In other experiments Mr Davy subjected other bodies to the action of the same power, with the view of effecting a decomposition. Thus, two cups of compact sulphate of lime, each containing about 14 grain measures of water, were connected by fibrous sulphate of lime moistened with pure water. The cups were filled with the same fluid, and they were introduced into the circuit of a galvanic battery with 100 pairs of plates of six inches. In five minutes the water in the positive cup became acid, while that in the opposite cup tinged turmeric. An hour after, a saturnine solution of lime was formed in the negative cup, and the other contained a solution of sulphuric acid of moderate strength.

Two cubical pieces of crystallized sulphate of strontites, of about an inch, with a hole drilled in each, capable of receiving eight grains of water, were plunged in pure water, in a platina crucible, and the level of the fluid was kept a few lines below the surface of the cubes. The holes in the earthy mineral were filled with pure water, and two platina wires were introduced into them. At the end of thirty hours the fluid in the cavity of the negative side precipitated solution of sulphate of potash, and sulphuric acid appeared in the other.

Two pieces of fluate of lime, having each a cavity, and connected by moist asbestos, were subjected to a similar experiment. The decomposition was slow; but in two days a solution of lime appeared in the one tube, and an acid in the other, which precipitated acetate of lead, and left a spot upon the glass, from which it was evaporated, so that it must have been fluoric acid,

Compact zeolite being prepared in the same way, and electrified in the same manner as the cube of Carrara marble, afforded soda and lime. Lepidolite, by similar treatment, gave potash; and an alkaline matter, which seemed to be a mixture of soda, potash and lime, was extracted from a piece of vitreous lava from Mount Etna.

The decomposition of saline bodies, which are soluble in water, was more rapid. A diluted solution of sulphate of potash introduced into the agate cups connected by amianthus moistened with pure water, being electrified by a battery with 50 pairs of plates, produced in four hours a weak solution of potash in the negative cup, and a solution of sulphuric acid in the positive cup. Similar phenomena were observed when sulphate of soda, nitrate of potash, nitrate of barytes, sulphate of ammonia, phosphate of soda, succinate, oxalate, and benzoate of ammonia and alum, were employed. The acids in a certain time collected in the tube containing the positive wire, and the alkalies and earths in the negative tube. Solutions of the muriatic salts, subjected to decomposition by the same processes, uniformly afforded oxymuriatic acid on the positive side.

Saturated saline solutions were most rapidly decomposed, but the smallest proportion was also acted on. Thus, if a piece of paper tinged with turmeric be plunged into pure water, in a proper circuit, in contact with the negative point, the minute quantity of saline compound contained in the paper, produces instantly a brown tint near its point of contact. Acid appears also from litmus paper at the positive surface.

Experiments were made with the view of ascertaining whether in these processes the separation of the constituent parts was complete, from the last portions of the compound. The following experiment shows that this is the case. "A very weak solution of sulphate of potash, containing 20 parts of water, and one part of saturated solution at 64°, was electrified in the two agate cups, by the power of 50 pairs of plates for three days; the connecting amianthus which had been moistened with pure water, was removed, washed with pure water, and again applied twice every day. By this precaution the presence of any neutral salt that might adhere to it, and disturb the results, was prevented. The alkali obtained in this process in the solution had the properties of pure potash, and when it had been saturated with nitric acid, it gave no turbidity by mixture with solution of muriate of barytes; the acid matter exposed to a strong heat, evaporated, without leaving any residuum."

Mr Davy then made experiments on the transfer of certain of the constituent parts of bodies, and also on the passage of acids, alkalies, and other substances, through various attracting chemical menstrua, by means of electricity, and in these experiments he obtained many curious and interesting results; but for an account of them, as well as of his observations on the different phenomena, and on the mode of decomposition and transition, we must refer to the memoir itself.

After the investigations in which Mr Davy had been occupied, and the singular and unexpected results which he obtained, he ventured to conclude, from the general principles on which the phenomena might be explained, that the new methods of proceeding would lead to "a more intimate knowledge concerning the true elements of bodies. Accordingly, in November 1807, he laid before the Royal Society a most interesting detail of an elaborate series of experiments on the decomposition of the alkalies.

Decomposition of the Alkalies.

In the first attempts that were made on the decomposition of potash, Mr Davy employed an aqueous solution, saturated at a common temperature. It was exposed to the action of a powerful galvanic battery, composed of 24 plates of copper and zinc of 12 inches square, 100 plates of six inches, and 150 plates of four inches square, charged with solutions of alum and nitrous acid. The action was very intense; a great deal of heat and violent effervescence were produced, but the water only of the solution was effected, and its hydrogen and oxygen were disengaged. Potash in the state of igneous fusion, in a spoon of platina, was next subjected to the action of a battery of 100 plates of six inches, highly charged. The spoon was connected with the positive side. In this experiment some brilliant phenomena were produced. The potash appeared to be a good conductor; and, while the communication was preserved, a most intense light was emitted from the negative wire, and a column of flame, seemingly owing to the development of combustible matter, arose from the point of contact. When the order was reversed, and the platina spoon was connected with the negative side, a vivid and constant light appeared at the opposite point. There was no inflammation round it; but aeriform globules, which inflamed in the atmosphere, rose through the potash. The platina was considerably acted on.

Although potash, when perfectly dry, be a non-conductor, it acquires a conducting power by being slightly moistened. A small piece of pure potash exposed for a few seconds to the atmosphere, was placed on a disc of platina connected with the negative side of a battery of 250 plates of six and four inches, in a state of intense activity. A platina wire from the opposite side was brought in contact with the upper surface of the alkali. A vivid action soon took place. The potash fused at both points of electrification; a violent effervescence appeared at the upper surface; but at the lower or negative surface no elastic fluid was emitted, but small globules like quicksilver were produced, some of which burnt with explosion and bright flame as they were formed, and others remained and were only tarnished, and finally covered by a white film formed on their surfaces. These globules were the bafs of potash. The same results were obtained, when gold and other metals, plumbago, or charcoal, were employed; and the effects were the same when the process was conducted in an exhausted receiver.

Mr Davy also obtained the same substance from potash, fused by means of a lamp, and placed in glass tubes confined by mercury, and furnished with hermetically inserted platina wires, to transmit the electricity; but the glass was rapidly dissolved by the action of the alkali, so that the process could not be long carried on.

In these experiments on potash, the combustible base was produced from the negative surface, and oxygen was evolved from the positive surface. The same effects invariably followed, when the experiment was conducted above mercury. The same thing was proved synthetically. The combustible substance obtained from the potash had its metallic lustre destroyed in the atmosphere, and a white crust formed upon it. This crust was found, upon examination, to be pure potash; but this was still farther confirmed by placing globules of the combustible matter in tubes containing common air, or oxygen gas, confined by mercury. An absorption of the oxygen took place, and a crust of alkali was formed upon the globule. When the combustible matter confined in given portions of oxygen, was strongly heated, a rapid combustion, with a brilliant white flame, was produced, and the metallic globules were converted into a white and solid mass, which was found to be pure potash.

To the combustible matter thus obtained from potash, Mr Davy gave the name of potassium. From its strong affinity for oxygen, it was extremely difficult to preserve it unchanged, for the purpose of examining its properties. The substance which he found to be least affected, is newly distilled naphtha. In this fluid potassium may be kept for many days nearly unaltered, and its physical properties may be examined in the atmosphere, when covered by a thin film of it.

Potassium, at 60° Fahrenheit, is in the form of small globules, which have the metallic lustre and general appearance of mercury; at 70° it becomes more fluid, and at 100°, different globules easily run into one. At 50° of Fahrenheit it is soft and malleable, and exhibits the lustre of polished silver. At 32° it becomes hard and brittle, and, when broken, presents a crystallized texture. To reduce it to vapour, it requires a red heat; and in proper circumstances, it may be subjected to distillation, without change. It is a good conductor of heat, and a perfect conductor of electricity.

In the properties now mentioned, potassium approaches nearly to the metals; but it is very different in its specific gravity. In naphtha of the specific gravity of .861 it rose to the surface; and it did not sink in double distilled naphtha, the specific gravity of which was about .770. From these and other experiments, Mr Davy estimates the specific gravity of potassium at .6, so that it is the lightest fluid body known. In its solid form it is somewhat heavier; but, even in this state, when cooled to 40° Fahrenheit, it swims in double distilled naphtha.

With the view of ascertaining the proportions of the constituent parts of potash, Mr Davy made two experiments, by subjecting the metallic base to combustion in oxygen gas. In the first experiment, .12 of a grain of potassium were employed; the combustion was made upon platina, and was rapid and complete, and the bafs appeared to be perfectly saturated. The result of this experiment indicates 86.7 of bafs, and 13.3 of oxygen, in the 100 parts of potash. In another experiment, the result he obtained was 85.5 of bafs, and 14.5 of oxygen. The mean of these two experiments is 86.1 of bafs, and 13.9 of oxygen, in 100 parts of potash.

The results of the decomposition of water by the bafs of the alkalies, which were more readily and perfectly obtained than those of their combustion, exhibited the proportion of base to be 84, and that of oxygen 16; but the mean of 86.1 of base, and 13.9 of oxygen, and 84 base and 16 oxygen, is 85 of potassium and 15 of oxygen, which may be taken as the proportions of the elements of potash.

Mr Davy's discoveries have been confirmed by the ingenious ingenious experiments of Thenard and Gay-Lussac. These distinguished chemists have decomposed potash by a different process. They introduced iron filings into a bent gun barrel, which was placed across a furnace. A tube with a stopcock, containing a quantity of solid potash, is connected with one extremity of the gun-barrel; to the other extremity there is attached a tube of safety, containing mercury, for the purpose of excluding the atmospheric air, and allowing any gaseous matter formed during the process to escape. The potash in the tube is to be kept cold by means of a freezing mixture, till that part of the barrel containing the iron filings has been raised to a white heat. The potash is then fused by applying heat, by means of a portable furnace; and it is allowed to pass through a small opening, to come in contact with the iron filings, where it is decomposed, the oxygen of the potash entering into combination with the iron, and the base passing on to the other extremity of the tube in a state of sublimation. At that extremity the metallic base is condensed by the application of excessive cold, and in this way the potassium may be obtained at less expense, and in greater quantity, than by means of galvanism. During this process, hydrogen gas is evolved, which, it is supposed, is owing to the decomposition of the water contained in the alkali. The potassium thus obtained is in the form of brilliant laminae, which adhere to the sides of the gun barrel. An alloy of the same metal with iron is also found in that part of the barrel containing the filings. Mr Davy has repeated this experiment, and he finds that the base obtained in this manner is heavier, and its melting point higher, than what is procured by means of galvanism. This, it is supposed, may arise from its being combined with a small proportion of iron. The metallic base of soda was obtained by a similar process.

But, according to the view which the French chemists have taken of these discoveries, and the results of their own experiments, they conclude, that the metallic substances derived from the alkalies are not simple, but are compounds of the several bases with hydrogen.

Another method of decomposing potash, and obtaining its base, which is still simpler, has been followed by Curaudau. In this process the decomposition is effected by charcoal. A mixture of carbonate of potash is made with flour or charcoal and linseed oil. This mixture is introduced into an iron or earthen tube or retort, and calcined, by gradually raising the heat, till a bluish light be seen in the inside of the vessel. Soon after an abundant evolution of vapour takes place, which is the base of the alkali, to be collected by introducing a clean iron rod, on which it condenses. Care must be taken to withdraw the rod before it is too hot, and to plunge it in oil of turpentine, under the surface of which the metallic crust on the rod may be separated. In this way a quantity of potassium may be procured. The base of soda is obtained by a similar process.

Fig. 3. is a representation of the apparatus employed by the French chemists in decomposing potash. ABCE is the gun barrel laid across the furnace, with its apparatus; D is the furnace, and F is the pipe of the bellows.

Fig. 4. is a section of the tube containing the potash.

But the chemical relations of potassium are not less extraordinary than its physical properties. It combines slowly with oxygen, and without flame, at all temperatures below that of its vaporization. At this point combustion takes place, with a brilliant white light, and intense heat. When it is heated slowly in a quantity of oxygen gas, which is not sufficient for its complete saturation, and at a temperature below that of inflammation, as for instance 400° of Fahrenheit, it changes to a red brown colour, and the solid form, consisting partly of potash, and partly of its base, is of a grayish colour. When exposed to water, or again heated in fresh quantities of air, the whole is converted into potash. When dry potash and potassium are fused together under proper circumstances, the base is deprived of its metallic splendour, and the two substances unite into a compound of a red brown colour when fluid, and of a dark gray when solid. This compound, when exposed to the air, soon absorbs its full proportion of oxygen, and is wholly converted into potash. The substance thus formed seems to be in a lower state of oxidation, so that it is to be considered as an oxide of potassium with a smaller proportion of oxygen.

When potassium is introduced into oxyuratic acid gas, it burns spontaneously with a bright red light, and a white salt is formed, which is muritate of potash. When a globule of potassium is heated in hydrogen gas, at a degree below its point of vaporization, it seems to dissolve in it, for the globule is diminished in volume, and the gas explodes with alkaline fumes, and bright light, when brought into the air; but, by cooling, the potassium is wholly or principally deposited, for the gas is deprived of its property of spontaneous detonation.

When potassium is thrown into water, it decomposes it with great violence; an instantaneous explosion, with brilliant flame, is produced, and a solution of pure potash is obtained. In these experiments, a white ring of smoke, gradually extending as it rises in the air, is produced, similar to the phenomenon of the combustion of phosphated hydrogen. When a globule of the basis of potash is placed upon ice, it instantly burns with a bright flame; part of the ice is melted, and in the cavity there is found a solution of potash.

By placing a globule of potassium upon moistened paper, tinged with tumeric, the moment that it comes in contact with the water, it burns, and, moving rapidly upon the paper, leaves behind it a deep reddish brown trace, thus demonstrating, in a very simple manner, the production of the alkali by the decomposition of water.

Potassium readily decomposes the small quantities of water contained in alcohol and ether, even in their purest state. As potash is insoluble in ether, when the base is thrown into it, oxygen is furnished to it, and hydrogen gas evolved, and, as the alkali is formed, the ether becomes white and turbid. It is observed, that the energy of action of potassium in ether and alcohol, is proportional to the quantity of water which they contain, and hydrogen and potash are always produced.

When potassium is thrown into solutions of the mineral acids, it inflames and burns on the surface, and when plunged, by proper means, beneath the surface enveloped in potash, surrounded by naphtha, it acts upon the oxygen with great intensity. In sulphuric acid, a white saline substance, covered with a yellow coating, which is supposed to be sulphate of potash surrounded with sulphur, and a gas, having the smell of sulphurous acid, and which is probably a mixture of that substance with hydrogen gas, are formed. When potassium is thrown into nitrous acid, nitrate of potash is formed, and nitrous gas is disengaged.

Potassium readily combines with phosphorus and sulphur. When pressed upon a piece of phosphorus, they both become fluid, enter into combustion, and produce phosphate of potash. When the experiment is made upon naphtha, no gaseous substance is given out; the compound has the appearance of a metallic phosphuret, is of the colour of lead, and has the lustre of polished lead. Exposed to the air at common temperatures, it combines slowly with oxygen, and is converted into phosphate of potash. When heated upon a plate of platina, it gives out fumes, but does not burn till it reaches the temperature of the rapid combustion of potassium.

When potassium is brought into contact with sulphur in fusion, in tubes filled with the vapour of naphtha, they combine rapidly, with the evolution of heat and light. A gray substance is thus formed, which has the appearance of artificial sulphuret of iron; if it be kept in fusion, it rapidly dissolves the glass. When this experiment is made in a glass tube, hermetically sealed, no gas is disengaged, if the tube be opened under mercury; but when it is made in a tube connected with a mercurial apparatus, a small quantity of sulphurated hydrogen is evolved. When the combination is effected in the atmosphere, a great inflammation takes place, and sulphuret of potash is formed, and by farther exposure to the air, it is at last converted into sulphate of potash.

When one part of potassium is added to eight or ten of mercury, in bulk, at 60° of Fahrenheit, they instantly unite, and form a substance like mercury in colour, but less coherent. When a globule is made to touch a globule of mercury about twice as large, they combine with considerable heat. The compound is fluid at the temperature of its formation, but, when cool, it becomes solid, with the appearance of silver. With the 1/8th of potassium to the weight of mercury, the amalgam is hard and brittle; but with one part of potassium, and 70 of mercury, it is soft and malleable. Exposed to the air, these compounds absorb oxygen, and deliquescent potash is formed; and in a few minutes the mercury is revived. A globule of the amalgam, thrown into water, decomposes it rapidly with a hissing noise; potash is formed; pure hydrogen is disengaged, and the mercury remains free. This amalgam dissolves all the metals, and even acts on iron and platina.

When potassium is heated with gold, silver, or copper, in a close vessel of pure glass, a rapid action is produced, and the compounds thrown into water effect its decomposition; potash is formed, and the metals are revived. Potassium forms an alloy with fusible metal, which has a higher point of fusion than the fusible metal itself.

Potassium has little effect on colourless and recently distilled naphtha: but, in naphtha, exposed to the air, it is soon oxidated, and an alkali which unites with the naphtha into a brown soap that collects round the globule, is formed. Potassium acts slowly on the concrete oils, as tallow, spermaceti, and wax, even when heated; coaly matter is deposited, a little gas is evolved, and a soap is formed. On the fluid fixed oils the effects are similar, but take place more slowly. With the assistance of heat, volatile oils are rapidly decomposed by potassium; gas is evolved, and charcoal deposited.

The metallic oxides, when heated in contact with potassium, are readily reduced. When a small quantity of oxide of iron was heated with it, to a temperature approaching its point of distillation, a vivid action took place. Alkali, in gray metallic particles, which effervesced in muriatic acid, appeared. The oxides of lead and tin were revived more rapidly, and with potassium in excess, an alloy was formed with the revived metal.

Potassium readily decomposes flint glass and green glass, by a gentle heat. The metallic oxides are reduced, and the alkali formed dissolves the glass. At a red heat, even the purest glass is acted on by potassium; the oxygen in the alkali of the glass seems to be divided between the potassium employed, and the potassium which is the base of the alkali in the glass, and thus effects an oxidation in the first degree.

Soda.—When pure soda was subjected in similar circumstances to the action of galvanism, similar results were obtained as from potash; but the decomposition required a more intense action in the battery, or it was necessary to have the alkali in thinner and smaller pieces. Potassium remained fluid at the temperature of the atmosphere, at the time of its production; but the base obtained from soda, which was fluid in the degree of heat of the alkali during its formation, became solid on cooling, and exhibited the lustre of silver. With a battery of 100 pairs of plates of six inches, in full activity, the decomposition of pieces of soda of about 15 to 20 grains in weight only could be effected; and it was necessary also that the distance between the wires should not exceed one-eighth or one-tenth of an inch. But when 250 pairs of plates were employed, highly charged for the decomposition of soda, the globules often burnt at the moment of their formation, and sometimes exploded and separated into smaller globules, which darted rapidly through the air, in a state of vivid combustion, producing a beautiful effect of continued jets of fire.

When the metallic base which is obtained from soda, and which Mr Davy has denominated sodium, was exposed to oxygen, it was converted into soda; and when this process was conducted by strongly heating the base in a given portion of oxygen, a rapid combustion with a brilliant white flame was produced, and the metallic globule was converted into a white solid mass, which was found to be soda. The oxygen gas was absorbed during the operation, and nothing was given out which affected the purity of the residual air.

The theory of the decomposition of the alkalies is stated by Mr Davy in the following words. "As in all decompositions of compound substances which I had previously examined, at the same time that combustible bases were developed at the negative surface in the electrical circuit, oxygen was produced, and evolved or carried-into combination at the positive surface, it was reasonable to conclude, that this substance was generated in a similar manner by the electrical action of the alkali; and a number of experiments made above mercury, with the apparatus for excluding external air, proved that this was the case. When solid potash or soda, in its conducting state, was included in glass tubes, furnished with electrified platina wires, the new substances were were generated at the negative surfaces; the gas given out at the other surface proved, by the most delicate examination, to be pure oxygen; and, unless when excess of water was present, no gas was evolved from the negative surface.

For the purpose of determining the proportions of the elements of soda, Mr Davy made similar experiments to those by which he ascertained the proportions of the base and oxygen of potash. By subjecting sodium to combustion in oxygen gas, it appeared that 100 parts of soda are composed of 80 of metallic base, and 20 of oxygen; but the results of its oxidation by the decomposition of water, indicated the proportions to be 23 of oxygen, and 77 of base. By taking the mean proportions, obtained from the results of the two sets of experiments, the elements of soda may be estimated at 78.5 of metallic base, and 21.5 of oxygen.

Sodium, which remains solid at common temperatures, is white and opaque; and examined under a film of naphtha, has the lustre and appearance of silver. It is very malleable, and softer than common metallic substances. With a slight pressure it spreads into thin leaves, and a globule of one-tenth or one-twelfth of an inch in diameter, is easily spread over a surface of one-fourth of an inch; and different globules are easily made to adhere, and form one mass by strong pressure. This property of welding which belongs to iron and platina at a white heat only, is not diminished when sodium is cooled to 32° Fahrenheit.

Sodium, like potassium, is a conductor of electricity and heat, and small globules subjected to galvanism inflame and burn with bright explosions. Sodium sinks in naphtha of specific gravity .861; but by mixing perfectly about 12 parts of naphtha, and five of oil of taffetas, the sodium remains at rest in any part of the fluid. This makes its specific gravity = about .9348, water being taken as 1. The particles of sodium lose their cohesion at 120° Fahrenheit. It becomes quite fluid at 180°, so that it readily fuses under boiling naphtha. The temperature at which it is volatilized is not ascertained, but it remains fixed in a state of ignition at the point of fusion of plate glass.

The chemical relations of sodium are analogous to those of potassium, but with some characteristic differences. Exposed to the atmosphere, it is immediately tarnished, and is gradually covered with a white crust, which is pure soda. It combines slowly with oxygen, and without any luminous appearance at common temperatures. When heated, the combination is more rapid, but no light is emitted till it acquire a temperature near that of ignition. The flame in oxygen gas is white, and it sends forth bright sparks, producing a very beautiful effect; in common air, the colour of the light is like that of the combustion of charcoal, but brighter. When sodium was heated in hydrogen gas, it seemed to have no action on it.

Sodium burns vividly in oxyuratic acid gas, giving out numerous sparks of a bright red colour; a saline matter is produced, which is muriate of soda. When sodium is thrown into water, it produces a violent effervescence with a loud hissing noise; it combines with the oxygen of the water to form soda, which is dissolved, and its hydrogen is disengaged. During the process there is no luminous appearance; but when sodium is thrown into hot water, a more violent decomposition takes place. A few scintillations are observed at the surface of the water, which is owing to small particles of the basis which are thrown out of the water, heated to such a degree as to burn in passing through the atmosphere. But when a globule of sodium is brought into contact with a small particle of water, or with moistened paper, the heat produced is usually sufficient for its combustion, as in this case there is no medium to carry off the heat rapidly.

Sodium produces similar effects with potassium when brought into contact with alcohol and ether. It acts with great energy on the strong acids; with nitric acid it produces a vivid inflammation, and with muriatic and sulphuric acids, great heat, but no light, is generated. The effects of sodium and potassium on the fixed and volatile oils, and naphtha, are quite analogous; but the appearances of the faponaceous compounds are somewhat different, the combinations with sodium being of a darker colour, and apparently less soluble.

Sodium also exhibits two degrees of combination with oxygen; the first is of a deep brown colour, which is fluid when produced, and becomes a dark gray solid on cooling. By attracting oxygen from the air, or by the decomposition of the water, it is converted into soda.

Sodium forms compounds with sulphur and phosphorus. In close vessels filled with the vapour of naphtha, it enters into combination with sulphur, giving out during the process a vivid light and heat, and often attended with explosion, from the vaporization of a portion of sulphur, and the disengagement of sulphurated hydrogen gas. The sulphuret of sodium is of a deep gray colour. In its combination with phosphorus, the compound obtained has the appearance of lead, and by exposure to the air, or by being subjected to combustion, the phosphuret of sodium is converted into phosphate of soda.

Sodium forms compounds with the metals. In the proportion of one-fortieth with mercury, a compound is obtained, which is of the colour of silver, and remains solid; the combination is accompanied with considerable heat. Sodium forms an alloy with tin, without producing any change of colour, and it has some action upon lead and gold when heated; but in its state of alloy it is soon converted into soda, by exposure to the air, or by the action of water, which it decomposes with disengagement of hydrogen. The amalgam of mercury and sodium seems to be capable of forming triple compounds with some other metals; and it would appear that iron and platina remain in combination with the mercury, after they are deprived of the sodium by exposure to the air. The same amalgam of sodium and mercury likewise forms combinations with sulphur; the triple compound thus obtained is of a dark gray colour.

Ammonia.—The chemical composition of ammonia has been many years considered as fully established; but in the course of Mr Davy's experiments on the decomposition of the fixed alkalies, it occurred to him that oxygen might also form one of the constituents of ammonia, and this he also proved by experiment. Charcoal carefully burnt, and deprived of moisture, was ignited by a galvanic battery of 250 pairs of plates of fix and four inches square, in a small quantity of pure ammonical gas, confined over mercury. A great expansion of the gaseous matter took place, and the white substance

Fig. 1. Fig. 2. Fig. 3. A B C D E F Fig. 4. Fig. 5. Fig. 6. Fig. 7. A B Fig. 8.

E. Mitchell Sculp. substance formed in the process collected on the sides of the glass tube. This matter effervesced in diluted muriatic acid, so that the product was probably carbonate of ammonia. A more decisive proof of ammonia containing oxygen as one of its elements, was obtained from another process. Very pure ammoniacal gas was passed over iron wire ignited in a platina tube, and two curved glass tubes were so arranged as to be inserted into a freezing mixture, and through one of these tubes the gas entered into the platina tube, to be conveyed through it by the other glass tube into an air-holder. The temperature of the air was 53°, and no sensible quantity of water was deposited in the cooled glass tube, which transmitted the unchanged ammonia. But after being exposed to heat, moisture was very perceptible, and the gas appeared in the air-holder densely clouded. This circumstance appeared to establish the formation of the water from the decomposition of ammonia during the process. But after the gas had been passed several times through the ignited tube, from one air-holder to the other, the iron wire was found superficially converted into oxide, and had increased in weight 746 of a grain. About four-tenths of a grain of water were collected from the cooled glass tubes by means of filtering paper, and 33.8 cubic inches of gas were expanded into 55.3 cubic inches, and by detonation with oxygen it was found, that the hydrogen gas in these was to the nitrogen or azote as 3.2 to 1 in bulk.

Ammonia was farther subjected to experiment by taking the electric spark in it. In experiments of this kind it was understood that it is resolved into hydrogen and azotic gases; but Mr Davy found, after observing several variations in the results, that the weight of the two gases obtained was less by about one-eleventh than the weight of the ammonia employed. He ascribes this loss to the oxygen of the alkali, which had probably combined with the wires of platina employed in the experiment, and had thus disappeared. From these experiments he estimates the proportion of oxygen in ammonia at not less than 7 or 8 parts in 100; and as the gases evolved may contain more water than the gas decomposed, the proportion may even be larger. By thus considering ammonia as a triple compound of azote, hydrogen, and oxygen, the phenomena of its production and decomposition admit of an easy explanation. In all cases in which ammonia is formed, oxygen exists along with its other elements, in the substances from the decomposition of which it is obtained. In the decomposition of ammonia, on the other hand, the oxygen which forms one of its elements, may be abstracted by the substance employed in its decomposition, or it may enter into combination with portions of its hydrogen or azote.

But in the progress of investigating the nature of ammonia, to which the attention of chemical philosophers has been particularly directed, it appears that this alkali is analogous to the fixed alkalies in having a metallic base. The Swedish chemists Berzelius and Pontin, placed mercury negatively electrified in the galvanic circle, in contact with solution of ammonia. By this action the mercury increased in volume, and after an expansion of four or five times its former dimensions, it became a soft solid. From this amalgam exposed to the air, mercury and ammonia are reproduced, with the absorption of oxygen; and when the amalgam is put into water it forms ammonia, with the evolution of hydrogen, and the re-appearance of the mercury in its metallic state. Mr Davy repeated this experiment, and he found that to produce an amalgam, from 50 or 60 grains of mercury, in contact with a saturated solution of ammonia, required a considerable time, and that this amalgam changed considerably, even in the short period that was necessary for removing it from the solution. Conceiving that the de-oxidation and combination with mercury might be more easily effected in its nascent state, he placed 50 grains of mercury in a cavity in muriate of ammonia. The muriate slightly moistened was placed on a plate of platina, and connected with the positive side of a large galvanic battery. The mercury was made negative by means of a platina wire; a strong effervescence, with much heat, immediately took place; the globule of mercury in a few minutes enlarged to five times its former dimensions. It had the appearance of amalgam of zinc. Metallic crystallizations shot from it as a centre round the body of salt. They had an arborecent appearance, often became coloured at their points of contact with the muriate, and when the connection was broken, rapidly disappeared, while ammoniacal fumes were given out, and the mercury was reproduced. With a piece of carbonate of ammonia, similar phenomena were exhibited. The amalgam was formed very rapidly; but when the galvanic action was powerful in this last case, a black matter appeared in the cavity, which was probably carbon, from the decomposition of the carbonic acid.

Mr Davy considering the strong attraction of potassium and sodium for oxygen, was led to examine whether they produced any effect in the amalgamation of ammonia, independent of electricity. With this view he united small portions of potassium and sodium with mercury, and brought them into contact with moistened muriate of ammonia. An amalgam was formed, which rapidly increased to six or seven times its volume, and the compound seemed to contain a larger proportion of ammoniacal base than that obtained by electricity. It appears, too, that a portion of the metallic base employed to effect the de-oxidation always remained in combination with the compound, so that it was not a pure amalgam. The following are the properties of the amalgam from ammonia, obtained by means of galvanism.

When this amalgam is formed at the temperature of 78° or 80°, it is in the state of a soft solid, of the consistence of butter; at 32° it becomes firmer, and assumes a crystallized form, in which small facets appear, which seem to be cubical. The amalgam of potassium crystallizes in cubes, as beautiful, and in some cases as large, as those of bismuth. The specific gravity of the amalgam is less than three, water being one. When the amalgam is thrown into water, a quantity of hydrogen equal to half its bulk, is evolved, and the water becomes a weak solution of ammonia. The amalgam being confined in a given portion of air, the air increases in bulk, and the mercury is revived. Ammoniacal gas equal to 1 1/2 or 1 1/3ths of the volume of the amalgam, is produced, and oxygen equal to one-seventh or one-eighth of the ammonia, disappears. When the amalgam is thrown into muriatic acid gas, it becomes instantly coated with muriate of ammonia, and a small portion of hydrogen is evolved. In sulphuric acid it Zinc becomes coated with sulphate of ammonia, and sulphur.

Mr Davy attempted, by various methods, to preserve the amalgam, in the hope of submitting it to distillation, for the purpose of obtaining the metallic base of the ammonia, which was united to the mercury, in a separate form. But as it is extremely difficult to free mercury, after being once moistened entirely from water, he did not succeed in this attempt. In wiping the amalgam carefully with bibulous paper, part of the ammonia was regenerated, and in passing it through fine linen, with the view of separating the moisture, a complete decomposition was effected, and the mercury was revived.

The quantity of the base of ammonia combined with 60 grains of quicksilver, appears not to exceed \( \frac{1}{750} \) of a grain, and the quantity of oxygen required for this is not more than \( \frac{1}{7500} \) of a grain of water, which might be supplied by merely breathing upon the amalgam. Mr Davy made various other experiments, with the view of ascertaining the nature and properties of the amalgam of ammonia; but for an account of these we must refer to the paper itself. And he observes, that the more these properties are considered, the more extraordinary will they appear. Mercury, by combination with about \( \frac{1}{7500} \) of its weight of new matter, becomes solid, and yet has its specific gravity reduced from 13.5 to less than 3, retaining at the same time its metallic characters, its colour, lustre, opacity, and conducting powers, undiminished. Can it then be conceived, Mr Davy asks, that a substance which forms with mercury so perfect an amalgam, should not be metallic in its own nature? This substance he denominates ammonium. On what then, it is farther asked, do the metallic properties of ammonium depend? Are hydrogen and nitrogen both metals in the gaseous state, at the usual temperature of the atmosphere; bodies of the same character, as zinc and mercury in the state of ignition? Or are these gases in their common form oxides which become metallized by de-oxidation? Or are they to be considered as simple bodies, not metallic in their own nature, but capable of composing a metal when deprived of oxygen, and becoming an alkali with the addition of oxygen?

In the farther prosecution of the experiments relative to the nature of ammonia, Mr Davy employed potassium. He brought ammonia into contact with about twice its weight of potassium at common temperatures; but excepting a slight diminution in the volume of the gas, and the metal losing its lustre and becoming white, no other effects were produced. The white crust when examined, proved to be potash, and a small portion of hydrogen was found in the ammonia, but not more than equal in volume to the metal. When the potassium was heated in the gas, by means of a spirit lamp applied to the bottom of the retort, (fig. 5,) the colour of the crust changed from white to bright azure, and gradually to bright blue, green, and dark olive. The crust and the metal then fused together. This process is attended with effervescence; and the crust passing off to the sides, exhibits the shining surface of the potassium. When heated a second time, it swells considerably, becomes porous, crystallized, and of a beautiful azure tint. A gas is evolved during this operation, which gives the same diminution by detonation with oxygen, as hydrogen, and ammonia disappears.

It has been observed that the proportion of ammonia which loses its elastic form, varies according as the gas employed contains more or less moisture. Thus, in ammonia saturated with water at 62° Fahrenheit, potassium caused the disappearance of twelve and a half cubical inches of ammonia; but in ammonia deprived of moisture, by exposure for two days to potash that had been ignited, the same quantity of potassium occasioned the disappearance of 16 cubical inches; but whatever were the degrees of moisture of the gas, the quantity of hydrogen generated always appeared equal for equal quantities of metal; and according to the French chemists, the portions are stated to have been the same as would have resulted from the action of water upon potassium. But in Mr Davy's experiments, the proportions were rather less. In one, conducted with great care, eight grains of potassium generated, by their action upon water, eight and a half cubical inches of hydrogen gas; and eight grains of potassium from the same mass, by their operation upon ammonia, produced 8\( \frac{1}{2} \) cubical inches of hydrogen gas. This difference, although inconsiderable, Mr Davy found always to take place.

In Mr Davy's experiments on the action of potassium on ammonia, he employed retorts of plate glass. The potassium was fastened upon trays of platina or iron, which were introduced into the glass retorts furnished with stop-cocks. The retorts were exhausted by an air-pump, then filled with hydrogen, exhausted a second time, and afterwards filled with ammonia. (See fig. 5. Fig. 5. and 6.)

The following are the properties of the substance obtained from the action of ammonia on potassium. 1. It is crystallized, and presents irregular facets, which are extremely dark, and in colour and lustre not unlike the green oxide of iron; it is opaque when examined in large masses, but is semitransparent in thin films, and appears of a bright brown colour by transmitted light. 2. It is fusible at a heat a little above that of boiling water, and if heated much higher, emits globules of gas. 3. It appears to be considerably heavier than water, for it sinks rapidly in oil of sassafras. 4. It is a non-conductor of electricity. 5. When it is melted in oxygen gas, it burns with great vividness, emitting bright sparks. Oxygen is absorbed, nitrogen is emitted, and potash, which from its great fusibility seems to contain water, is formed. 6. When brought into contact with water, it acts upon it with much energy, produces heat, and often inflammation, and evolves ammonia. When thrown upon water, it disappears with a hissing noise, and globules from it often move in a state of ignition upon the surface of the water. It rapidly effervesces and deliquesces in air, but can be preserved under naphtha, in which, however, it softens slowly, and seems partially to dissolve. When it is plunged under water filling an inverted jar, by means of a proper tube, it instantly disappears with effervescence, and the non-absorbable elastic fluid liberated is found to be hydrogen gas.

It is found that the weight of this substance is greater than that of the potassium from which it is formed; and from this it is concluded, that part of the ammonia, or of its elements, enters into its composition. When this substance is decomposed by heat, nitrogen and hydrogen gases, with a portion of ammonia, are given out. It appears, however, that the production of the ammonia is is in proportion to the moisture admitted, and when the moisture is considerable, the whole product is ammonia. When this substance is exposed to heat, a matter remains, which even by increasing the heat, is no farther changed. On this residuum water acts violently, and with effervescence, from the evolution of hydrogen gas. Ammonia and potash are at the same time reproduced. Mr Davy's conclusion from these experiments is, that the substance formed by the action of ammonia on potassium is a compound of the latter with a small proportion of oxygen and nitrogen; and as it is found that the quantity of hydrogen given out during its formation is nearly equal to the hydrogen contained in the ammonia, it follows that neither hydrogen nor the ammonia itself can be supposed to enter into its composition.

In prosecuting this investigation, Mr Davy made various experiments, and whether the substance was acted on by water, exposed to the action of oxygen, or decomposed by heat, it was found, contrary to expectation, that the quantity of nitrogen evolved during its decomposition was much less than in proportion to the quantity of ammonia which had disappeared in its formation. In one experiment, in which the decomposition was effected by heat, the gaseous product was examined, and was found to be partly potash, and partly potassium; but it afforded no traces of ammonia, when acted on by water, which is a proof that it retained no nitrogen. In another experiment, 11 cubic inches of ammonia, or 2.05 grains, were decomposed by potassium. The product was 3.6 cubic inches of nitrogen, equal to 1.06 grain; 16 cubic inches of hydrogen, equal to .382 grain; and there was added to the potassium a quantity of oxygen equal to .6 grain. These products taken together amount to 2.04 grains, which is nearly equal to the quantity of ammonia employed; but this quantity of ammonia, if the proportions of its elements be estimated, from its decomposition by electricity, would have yielded 5.5 cubic inches of nitrogen, equal to 1.6 grain, and only 14 cubic inches equal to .33; and allowing the separation of oxygen in this process in water, it cannot be estimated at more than .11 or .12; and hence, if the analysis of ammonia by electricity come near to accuracy, there is in this process a considerable loss of nitrogen, and the production of oxygen and hydrogen.

How, says Mr Davy, can these extraordinary results be explained? The decomposition and composition of nitrogen seem proved, and one of its elements appears to be oxygen; but what is the other element? Is the gas that appears to possess the properties of hydrogen a new species of inflammable aeriform substance? Or has nitrogen a metallic base, which alloys with the iron or platinum? Or is water alike the ponderable matter of nitrogen, hydrogen, and oxygen? Or is nitrogen a compound of hydrogen, with a larger proportion of oxygen than exists in water? Of these important questions, Mr Davy adds, the two first seem the least likely to be answered in the affirmative, from the correspondence between the weight of the ammonia decomposed, and the products, supposing them to be known substances.

In concluding this subject, we must observe, that it still remains in a considerable degree of obscurity. It seems, however, to be ascertained, that the base of ammonia is of a metallic nature, which must be derived, either from the nitrogen or the hydrogen, or from both, or perhaps these substances are only different forms of combination of the elementary base. Or if nitrogen be supposed to be an oxide of hydrogen, then hydrogen in its gaseous form is either a metallic substance, or has a metallic base, which latter enters into combination with the mercury employed in the decomposition of ammonia.

Decomposition of the Earths.

From the results of the experiments on potash and soda, which Mr Davy obtained, he was led to entertain the strongest hopes of being able to effect the decomposition both of the alkaline and common earths; and the phenomena which took place in the first imperfect trials made upon these bodies countenanced the ideas, that had obtained since the earliest periods of chemistry, of their being metallic in their nature.

The earths, like the fixed alkalies, are non-conductors of electricity; but the fixed alkalies become conductors by fusion: the infusible nature of the earths, however, rendered it impossible to operate upon them in this state: the strong affinity of their bases for oxygen, made it unavailing, to act upon them in solution in water; and the only methods that proved successful, were those of operating upon them by electricity in some of their combinations, or of combining them at the moment of their decomposition by electricity in metallic alloys, so as to obtain evidences of their nature and properties. To render the experiments upon the earths satisfactory, a more powerful battery will be required, than Mr Davy has a prospect of seeing very soon constructed; he therefore prefers the imputation of having published unfinished labours, to that of having concealed any new facts.

Barytes, stontites, and lime, slightly moistened, were electrified by iron wires under naphtha, by the same methods, and with the same powers, as those employed for the decomposition of the fixed alkalies. In these cases gas was copiously evolved, which was inflammable; and the earths, where in contact with the negative metallic wires, became dark-coloured, and exhibited small points, having a metallic lustre, which, when exposed to air, gradually became white: they became white likewise when plunged under water; and when examined in this experiment with a magnifier, a greecish powder seemed to separate from them, and small globules of gas were disengaged.

In these experiments there was great reason to believe that the earths had been decomposed; and that their bases had combined with the iron, so as to form alloys decomposable by the oxygen of the air or water; but the indistinctness of the effect, and the complicated circumstances required for producing it, were such as to compel Mr Davy to form other plans of operation.

Mr Davy bearing in mind the strong attraction of potassium for oxygen, was induced to try whether this body might not detach the oxygen from the earths, in the same manner as charcoal decomposes the common metallic oxides. He heated potassium in contact with dry pure lime barytes, stontites, and magnesia, in tubes of plate-glass; but as he was obliged to use very small quantities, and as he could not raise the heat to ignition without fusing the glass, he obtained no good results in this manner. The potassium appeared to act upon the earths and on the glaas, and dark brown substances were obtained, which evolved gas from water; but no distinct metallic globules could be procured: from these, and other like circumstances, it seemed probable, that though potassium may partially deoxygenate the earths, yet its affinity for oxygen, at least at the temperature employed, is not sufficient to effect their decomposition. Mr Davy, having made mixtures of dry potash in excess and dry barytes, lime, strontites, and magnesia, brought them into fusion, and acted upon them in the galvanic circuit in the same manner as he employed for obtaining the metals of the alkalies. He expected that the potassium and the metals of the earths might be deoxygenated at the same time, and enter into combination in alloy.

In this way of operating, the results were more distinct than in the last: metallic substances appeared less fusible than potassium, which burned the infant after they had formed, and which by burning produced a mixture of potash and the earth employed. An attempt was made to form the metallic substances under naphtha, but without much success. To produce the result at all, required a charge by the action of nitric acid, which the state of the batteries would not often allow of; and the metal was generated only in very minute films, which could not be detached by fusion, and which were instantly destroyed by exposure to air.

Mr Davy had found in his researches upon potassium, that when a mixture of potash and the oxide of mercury, tin, or lead, was electrified in the galvanic circuit, the decomposition was very rapid, and an amalgam, or an alloy of potassium, was obtained; the attraction between the common metals and potassium apparently accelerating the separation of the oxygen. The idea that a similar kind of action might affect the decomposition of the alkaline earths, induced him to electrify mixtures of these bodies and the oxide of tin, of iron, of lead, of silver, and of mercury; and these operations were far more satisfactory than any of the others.

A mixture of two-thirds of barytes, and one-third of oxide of silver very slightly moistened, was electrified by iron wires; an effervescence took place at both points of contact, and a minute quantity of a substance, possessing the whiteness of silver, formed at the negative point. When the iron wire to which this substance adhered, was plunged into water containing a little alum in solution, gas was disengaged, which proved to be hydrogen; and white clouds, which were found to be sulphate of barytes, descended from the point of the wire.

A mixture of barytes and red oxide of mercury, in the same proportions, was electrified in the same manner. A small mass of solid amalgam adhered to the negative wire, which evidently contained a substance, that produced barytes by exposure to the air, with the absorption of oxygen; and which occasioned the evolution of hydrogen from water, leaving pure mercury, and producing a solution of barytes.

Mixtures of lime, strontites, magnesia, and red oxide of mercury, treated in the same manner, gave similar amalgams, from which the alkaline earths were regenerated by the action of air or water, with like phenomena; but the quantities of metallic substances obtained were exceedingly minute; they appeared as mere superficial formations surrounding the point of the wire, nor did they increase after the first few minutes of electrization, even when the process was carried on for some hours.

These experiments were at first made when the batteries were in bad order; but were afterwards resumed with a new and much more powerful apparatus, constructed in the laboratory of the Royal Institution, and consisting of five hundred pairs of double plates of six inches square.

When Mr Davy attempted to obtain amalgams with this apparatus, the transmitting wires being of platina, of about \( \frac{1}{4} \) of an inch diameter, the heat generated was so great as to burn both the mercury and basis of the amalgam at the moment of its formation; and when, by extending the surfaces of the conductors, this power of ignition was modified, yet still the amalgam was only procured in thin films, and globules sufficiently large to submit to distillation could not be procured. When the transmitting wires were of iron of the same thickness, the iron acquired the temperature of ignition, and combined with the bases of the earths in preference to the mercury; and metallic alloys of a dark gray colour were obtained, which acted on water with the evolution of hydrogen, and were converted into oxide of iron and alkaline earths.

While Mr Davy was engaged in these experiments, he received a letter from Professor Berzelius of Stockholm, who stated that in conjunction with Dr Pontin, he had succeeded in decomposing barytes and lime, by negatively electrifying mercury in contact with them, and that in this way he had obtained amalgams of the metals of these earths.

Mr Davy immediately repeated these operations with perfect success; a globule of mercury, electrified by the power of the battery of 500, weakly charged, was made to act upon a surface of slightly moistened barytes, fixed upon a plate of platina. The mercury gradually became less fluid, and after a few minutes was found covered with a white film of barytes, and when the amalgam was thrown into water, hydrogen was disengaged, the mercury remained free, and a solution of barytes was formed.

The result with lime, as these gentlemen had stated, was precisely analogous. Strontites and magnesia were decomposed in the same manner.

From strontites the expected result soon took place; but from magnesia, in the first trials, no amalgam could be procured. By continuing the process, however, for a longer time, and keeping the earth continually moist, at last a combination of the basis with mercury was obtained, which slowly produced magnesia by absorbing oxygen from the air, or by the action of water.

Mr Davy found that all these amalgams might be preserved for a considerable period under naphtha. In length of time, however, they became covered with a white crust under this fluid. In water, the amalgam of barytes was most rapidly decomposed; that of strontites and that of lime next in order: but the amalgam from magnesia, as might be expected from the weak affinity of the earth for water, very slowly changed. When a little sulphuric acid was added to the water, however, the evolution of hydrogen, and the production and solution of magnesia, were exceedingly rapid, and the mercury soon remained free.

Mr Davy believed, that one reason why magnesia was less easy to metallize, than the other alkaline earths, was owing to its insolubility in water, which would prevent it from being presented in the nascent state, detached from its solution at the negative surface.

He then made the experiment, using moistened sulphate of magnesia instead of the pure earth; and the amalgam was much sooner obtained. Here the magnesia was attracted from the sulphuric acid, and probably deoxygenated and combined with the quicksilver at the same instant.

The amalgams of the other bases of the alkaline earths could be obtained in the same manner from their saline compounds: muriate and sulphate of lime, the muriate of strontites and barytes, and nitrate of barytes, were decomposed by the same means as the other earths. The earths, separated at the deoxygenating surface, there seemed instantly to undergo decomposition, and, feised upon by the mercury, were in some measure defended from the action of air, and from the contact of water, and preserved by their strong attraction for this metal.

In attempting to procure the metals of the alkaline earths, the latter were slightly moistened, and mixed with one-third of red oxide of mercury; the mixture was placed on a plate of platina; a cavity was made in the upper part of it to receive a globule of mercury, of from 50 to 60 grains in weight; the whole was covered by a film of naphtha, and the plate was made positive, and the mercury negative, by a proper communication with the battery of five hundred.

The amalgams obtained in this way were distilled in tubes of plate-glas, or in some cases in tubes of common glas. These tubes were bent in the middle, and the extremities were enlarged and rendered globular by blowing, so as to serve the purposes of a retort and receiver. The tube, after the amalgam had been introduced, was filled with naphtha, which was afterwards expelled, by boiling, through a small orifice in the end corresponding to the receiver, which was hermetically sealed when the tube contained nothing but the vapour of naphtha, and the amalgam. It was found immediately that the mercury rose pure by distillation from the amalgam, and it was very easy to separate a part of it; but to produce a complete decomposition was very difficult, as nearly a red heat was required for the purpose, and as at a red heat the bases of the earths instantly acted upon the glas, and became oxygenated. When the tube was large in proportion to the quantity of amalgam used, the vapour of the naphtha furnished oxygen sufficient to destroy part of the bases: and when a small tube was employed, it was difficult to heat the part used as a retort sufficient to drive off the whole of the mercury from the bases, without raising too highly the temperature of the part serving for the receiver, so as to burst the tube.

In consequence of these difficulties, in a multitude of trials, only a very few successful results were obtained; and in no case could our author be absolutely certain, that there was not a minute portion of mercury still in combination with the metals of the earths.

In the best result obtained from the distillation of the amalgam of barytes, the residuum appeared as a white metal, of the colour of silver. It was fixed at all common temperatures, but became fluid at a heat below redness, and did not rise in vapour when heated to redness, in a tube of plate-glas, but acted violently up-

on the glas, producing a black mass, which seemed to contain barytes, and a fixed alkaline base, in the first degree of oxygenation. When exposed to air, it rapidly tarnished, and fell into a white powder, which was barytes. When this process was conducted in a small portion of air, the oxygen was absorbed and the nitrogen remained unaltered; when a portion of it was introduced into water, it acted upon it with great violence and sunk to the bottom, producing in it barytes; and hydrogen was generated. From the minuteness of the quantities obtained, neither its physical nor chemical qualities could be examined correctly. It sunk rapidly in water, and even in sulphuric acid, though surrounded by globules of hydrogen, equal to two or three times its volume; from which it seems probable, that it cannot be less than four or five times as heavy as water. It flattened by pressure, but required a considerable force to produce this effect.

The metal from strontites sunk in sulphuric acid, and exhibited the same characters as that from barytes, except in producing strontites by oxidation.

The metal from lime, Mr Davy has never been able to examine, either when exposed to air, or when under naphtha. In the case in which he was able to distil the quicksilver from it to the greatest extent, the tube unfortunately broke, while warm, and at the moment that the air entered, the metal, which had the colour and lustre of silver, instantly took fire, and burned with an intense white light into quicklime.

The metal from magnesia seemed to act upon the glas, even before the whole of the quicksilver was distilled from it. In an experiment in which the process was stopped before the mercury was entirely driven off, it appeared as a solid; having the same whiteness and lustre as the metals of the other earths. It sunk rapidly in water, though surrounded by globules of gas producing magnesia, and quickly changed in air, becoming covered with a white crust, and falling into a fine powder, which proved to be magnesia.

In several cases in which amalgams of the metals were obtained, containing only a small quantity of mercury, they were exposed to air on a delicate balance, and it was always found, that, during the conversion of metal into earth, there was a considerable increase of weight.

Mr Davy endeavoured to ascertain the proportions of oxygen and base in barytes and strontites, by heating amalgams of them in tubes filled with oxygen, but without success. He satisfied himself, however, that when the metals of the earths were burned in a small quantity of air, they absorbed oxygen, gained weight in the process, and were in the highly caustic or unflaked state; for they produced strong heat by the contact of water, and did not effervescence during their solution in acids.

The evidence for the composition of the alkaline earths is then of the same kind as that for the composition of the common metallic oxides; and the principles of their decomposition are precisely similar, the inflammable matters in all cases separating at the negative surface in the galvanic circuit, and the oxygen at the positive surface.

Mr Davy has denominated the metals obtained from the alkaline earths, barium, strontium, calcium, and magnesium.

In attempting the decomposition of the other earths, Mr Davy was less fortunate in obtaining distinct results; and he observes that the methods which have usually proved successful, as well as some others, failed. When alumina was subjected to the action of electricity, it was in a state of fusion with potash. In this process metallic globules were produced, but they consisted chiefly of the base of the alkali. Some appearances, however, showed, that the alumina itself was decomposed; for when soda was employed, the metallic product obtained was less fusible than sodium itself, and when it was acted on by water, it produced soda and a white powder. When potash was fused with the alumina, and subjected to galvanic action, the metallic product decomposed water with great rapidity, and the solution obtained deposited alumina by the action of an acid. When potassium in the state of amalgam, with one-third of mercury, in contact with alumina, was negatively electrified under naphtha, and after the process had been continued for some time, the amalgam was added to water, a decomposition took place, and a solution was obtained, which produced a cloudiness on the addition of an acid; but all these results are to be considered as very imperfect evidence of the decomposition of alumina.

Mr Davy was still less successful in attempting the decomposition of silica, partly from its insolubility, and partly from its being scarcely, if at all, affected with electricity, when diffused in water, and placed in the galvanic circuit; but by following the same processes as in his experiments on alumina, some indications of decomposition appeared. When silica was fused with six parts of potash, and was placed in fusion in the galvanic circuit, metallic matter was obtained, from which, by exposure to the air, or by dropping it into water, a minute quantity of silica was reproduced. When potassium, amalgamated with one-third of mercury, and in contact with silica, was negatively electrified, he obtained a similar result; but in none of the experiments could the product obtained be considered as the pure base of the earth.

The earths of zirconia and glucina were also subjected to the action of galvanism, by processes similar to those which have now been described, and in both there were some indications of decomposition; but the results were not so perfect as to lead to any certain conclusion respecting their nature.

Decomposition of Sulphur and Phosphorus.

Sulphur.—Sulphur, which had formerly been considered as a simple substance, appears, from the experiments of some of the French chemists, and particularly those of Berthollet junior, to be a compound of sulphur and hydrogen. The latter chemist, in his experiments to investigate the nature of this substance, caused sulphur to pass through a coated glass tube, which was heated to whiteness; some indications of sulphurated hydrogen were obtained. He then formed metallic sulphures, as of iron, copper, and mercury, and in these processes, which were performed in an earthen retort with great care, sulphurated hydrogen gas was also obtained. Water in the state of vapour being passed over sulphur in fusion, caused the evolution of sulphurated hydrogen; the water was not decomposed, for no trace of acid could be observed. It seemed only to have effected the disengagement of hydrogen from the sulphur.

Mr Davy, in the course of his experiments in galvanism, subjected sulphur to the action of that power. The sulphur which he employed was sublimed in a retort, filled with azotic gas, and it was kept hot till the commencement of the experiment. The reason of this preliminary process was, to avoid any uncertainty which might arise from water absorbed by the sulphur. The sulphur introduced into a curved tube, fig. 7, which was furnished with wires of platina A and B, the upper wire A being hermetically sealed into the end of the tube, was then placed in the galvanic circuit of a battery of 500 pairs of plates of fix inches, in a state of great activity. A very intense action followed, accompanied by great heat and a brilliant light. The sulphur soon entered into ebullition, and gave out a great quantity of elastic fluid, a good deal of which was permanent. The sulphur itself assumed a deep red brown colour. The gas obtained was sulphurated hydrogen. In another experiment made on 200 grams of sulphur, the amount of sulphurated hydrogen obtained was equal to more than five times the volume of the sulphur. A considerable action was observed to have taken place on the wires of platina; and the sulphur, at its point of contact with the wires, reddened moist litmus paper. When sulphur and potassium are heated together, a very powerful action takes place. Sulphurated hydrogen is disengaged with very intense heat and light. From these experiments the conclusion seems fair and obvious, that hydrogen exists in sulphur, for a substance, as Mr Davy observes, which can be produced from it in such abundance, is not to be considered merely as an accidental ingredient.

But as it is admitted that sulphurated hydrogen contains oxygen, Mr Davy contends that oxygen is to be regarded as one of the constituents of sulphur. In this opinion he is supported by experiment. He heated potassium in sulphurated hydrogen gas, from which moisture had been as much as possible abstracted, by muriate of lime. The potassium took fire, and burnt with a brilliant flame. When four grains of potassium were heated in 20 cubic inches of gas, the quantity of gas diminished only about 2 1/2 cubic inches; but the properties of the gas were totally changed. A small portion only of it was absorbed by water, and the remainder was hydrogen, holding in solution a minute portion of sulphur. Some sulphur was observed on the sides of the retort, and a solid matter was formed, which on the surface was of a red colour, like sulphuret of potash, but internally dark gray, like sulphuret of potassium. By subjecting this substance to the action of muriatic acid, sulphurated hydrogen gas was obtained, but the proportion was less than would have been given out, had the potassium been in combination with pure combustible matter. From this Mr Davy concludes, that there is a principle in sulphurated hydrogen which is capable of destroying partially the inflammability of potassium, and of producing upon it all the effects of oxygen. As sulphurated hydrogen is obtained by heating sulphur strongly in hydrogen gas, Mr Davy introduced four grains of sulphur in a glass retort, containing about 20 cubic inches of hydrogen, and by means of a spirit lamp, he raised the heat nearly to redness. No perceptible change took place in the volume of the gas after the process. The sublimed sulphur was unchanged in its properties, and about three cubic inches of unelastic fluid, absorbable by water, reddening litmus, and having all the properties of sulphurated hydrogen gas, were formed. Supposing then Zinc. sulphurated hydrogen to be constituted by sulphur diffused in its unchanged state in hydrogen, and admit the existence of oxygen in this gas, its existence must likewise be allowed in sulphur. From these experiments Mr Davy thinks it not unreasonable to assume, that sulphur in its common state is a compound of small quantities of oxygen and hydrogen, with a large quantity of a base, which produces the acids of sulphur in combustion; and as this basis, it is added, possesses strong attractions for other bodies, it will probably be very difficult to obtain it in its uncombined state.

Sulphur combines readily with potassium, when brought into contact in tubes filled with the vapour of naphtha; heat and light are rapidly evolved during the combination, and a gray substance like artificial sulphuret of iron, is produced. The sulphurated hydrogen in small quantity is formed at the moment of combination, the hydrogen of which, it is supposed, is derived from the sulphur. The sulphuret of potassium readily inflames, and when exposed to the air, it is gradually oxidated, and converted into sulphate of potash.

Sulphur also enters into combination with sodium, accompanied also with the evolution of heat and light. An explosion sometimes takes place, which is owing to the volatilization of a portion of sulphur, and the disengagement of sulphurated hydrogen gas. The sulphuret of sodium is of a deep gray colour.

Phosphorus.—Mr Davy subjected phosphorus to similar experiments, and he found that the same analogies are applicable to this combustible. Common electrical sparks transmitted through phosphorus produce no evolution of permanent gas; but when acted upon by the same galvanic battery, and in the same circumstances as the sulphur, a considerable evolution of gas was effected, and the phosphorus became of a deep red brown colour. The gas was phosphorated hydrogen; and in an experiment continued for some hours, the quantity evolved was four times the volume of the phosphorus. The light by the galvanic spark was at first a brilliant yellow, and afterwards orange.

Three grains of potassium were heated in 16 cubical inches of phosphorated hydrogen. As the fusion was effected, the retort was filled with white fumes, and a reddish substance was deposited upon the upper part and sides; the heat was applied for some minutes, but no inflammation took place. When the retort cooled, the absorption was less than a cubical inch; the potassium externally was of a deep brown, and internally of a lead colour. The residual gas seemed to contain in solution a little phosphorus, but it had not the property of spontaneous inflammation. While the phosphuret was acted upon over mercury by a solution of muriatic acid, it gave out only \( \frac{1}{4} \) cubical inch of phosphorated hydrogen.

One grain of potassium, and one of phosphorus, were fused together. In combining, a very vivid light and intense ignition were produced; \( \frac{1}{5} \) of a cubical inch of phosphorated hydrogen was evolved, and the phosphuret, with diluted muriatic acid over mercury, gave out \( \frac{1}{10} \) of a cubical inch of phosphorated hydrogen. In another experiment with one grain of potassium, and three of phosphorus, nearly one-fourth of a cubical inch of phosphorated hydrogen was obtained; but the compound yielded by muriatic acid, only \( \frac{1}{50} \) of a cubical inch.

From these experiments it is concluded, that phosphorated hydrogen contains a minute proportion of oxygen, and consequently that the same element enters into the composition of phosphorus. The deficiency of phosphorated hydrogen in the last experiment can only be referred to the supply of oxygen to the potassium from the phosphorus; and the quantity of phosphorated hydrogen produced in the experiment with equal parts of potassium and phosphorus, is much less than could be expected, if the potassium and phosphorus consisted merely of pure combustible matter.

Mr Davy also instituted a set of interesting experiments on the states of the carbonaceous principle in plumbago, charcoal, and the diamond, and the results of these are detailed in the same memoir; but for an account of them we must refer to the paper itself.

Decomposition of Boracic, Fluoric, and Muriatic acids.

The properties of boracic, fluoric, and muriatic acids, many of which are quite analogous to those of other acids whose elements have been discovered, have led chemists to conclude that oxygen is also the acidifying principle in the former; but the separate existence or nature of the base of these three acids was, till the late researches of galvanism were instituted, utterly unknown. The investigation of the nature of these substances has been prosecuted by Mr Davy, and some of the French chemists; and of their experiments we shall now give a very short account.

Boracic acid.—When boracic acid was moistened with water, and exposed between two surfaces of platina, and then subjected to the battery of 500 plates, an olive brown matter formed on the negative surface, and, increasing in thickness, appeared at last almost black. This substance was permanent in water, but it dissolved and effervesced in warm nitrous acid. Heated to redness on the platina, it burned slowly, and gave off white fumes, which reddened moistened litmus paper. A black mass remained, which through a magnifier appeared vitreous, and seemed to contain a fixed acid. The inference drawn from this experiment is, that the acid was decomposed, and again by the latter process reproduced.

When equal weights of potassium and boracic acid were heated together in a green glass tube, which had been exhausted, after being twice filled with hydrogen gas, an intense ignition, with vivid inflammation, where the potassium was in contact with the boracic acid, took place, even before the temperature approached near to a red heat. When the acid had been heated to whiteness, before being introduced into the tube, and powdered and used while yet warm, the quantity of gas which was hydrogen, given out in the operation, did not exceed twice the volume of the acid. In this mode of conducting the experiment, 12 or 14 grains of each of the two substances only could be employed, on account of the intense heat and consequent fusion of the glass tube with larger proportions. Mr Davy found in several experiments, in which he employed equal parts of acid and potassium, that a great proportion of the former remained undecomposed, and he ascertained that twenty grains of potassium had their inflammability destroyed by eight grains of boracic acid.

To collect the substances formed in the process, metallic tubes with stop-cocks, and exhausted, after being filled with hydrogen, were employed. With tubes of brass or copper, a dull red heat only, but with iron tubes, a white heat was applied; and in all cases the acid was decomposed with the same results. The substance obtained from the iron tube was in some parts of a dark olive colour, and in others almost black. It did not effervescence with warm water, but was rapidly acted upon by it. The solutions obtained consisted of subcarbonate of potash, and potash.

The following are the properties of the substance obtained in the decomposition of boracic acid by means of processes conducted in brass tubes, which afforded it in largest proportion. To this substance Mr Davy has given the name of boracium, which, as it is produced in the manner now described, is in the form of a pulverulent mass of the darkest shades of olive; it is opaque, very friable; the powder does not scratch glass, and is a non-conductor of electricity. Dried at 100° or 120°, it gives off moisture, by decreasing the temperature; and when heated in the atmosphere, takes fire at a temperature below the boiling point of olive oil, emitting a red light, and sparks like charcoal. When excluded from air, and subjected to a white heat in a platina tube, exhausted after being filled with hydrogen, it remains unchanged, excepting in becoming a little darker, and acquiring a greater specific gravity.

Boracium introduced into a retort filled with oxygen gas, and heated by a spirit lamp, throws off vivid scintillations like those of the combustion of the bark of charcoal, and the mass gives out a brilliant light. A sublimate appears, which is boracic acid; it becomes coated with a vitreous substance, which is also found to be the same acid. When this is washed off, the black residuum requires a greater heat, but it is also inflamed, and converted into boracic acid. When boracium is brought into contact with oxy-muriatic acid gas, at common temperatures, it immediately takes fire, and burns with a brilliant white light, coating the inside of the vessel with a white substance, which is boracic acid. Boracium heated to redness with hydrogen or nitrogen, became of a darker colour, and gave out a little moisture, but remained otherwise unchanged. Thrown into concentrated nitric acid, it rendered it bright red; nitrous gas was produced and absorbed, but no rapid solution took place till the acid was heated, when the boracium disappeared with effervescence, and the evolution of nitrous gas, and the fluid yielded boracic acid. The action of boracium on sulphuric and muriatic acids was not remarkable. It combined with the fixed alkalies, both by fusion and aqueous solution, and formed pale olive-coloured compounds, which by muriatic acid were precipitated of a dark colour. When fused with sulphur, it diffused slowly, and the sulphur became of an olive colour. Its action with phosphorus in the same circumstances was still feebler, but it communicated a shade of pale green.

From the experiments now detailed, it appears that boracium obtained by means of potassium, is different from any other known species of matter, and seems to be the same as that obtained from boracic acid by electricity. According to the result of experiments made by Mr Davy, boracic acid is composed of one part of boracium, and about 1.8 of oxygen; and supposing the dark residual substance to be an oxide, it consists of 4.7 of boracium, and 1.55 of oxygen.

For an account of the experiments of Gay Lussac and Thenard, in investigating the nature of boracic acid, see Jour. de Physique, tom. Ixvii. or Nichol. Jour. xxiii. 260.

Fluoric acid.—According to the experiments of Mr Davy, potassium, when heated in fluoric acid gas, undergoes combustion, and a great absorption of the gas takes place. In other experiments, he found, that when fluoric acid gas, procured in contact with glass, is introduced into a plate glass retort, exhausted after being filled with hydrogen gas, white fumes appear from the action of the potassium, which looses its splendour, and becomes coloured with a gray crust. The fumes are more copious when the bottom of the retort is gently heated. The volume of the gas examined at this time appears to be a little increased, with the addition of hydrogen; and when the temperature is raised nearly to the point of sublimation of the potassium, the metal rises through the crust, becomes first of a copper colour, and then inflames and burns with a brilliant red light. After this combustion, the fluoric acid is either wholly or partially destroyed, according as the quantity of potassium is great or small; and a mass of a chocolate colour is found in the bottom of the retort; the sides and the top are lined with a sublimate, which is partly chocolate, and partly of a yellow colour. When the residual gas is washed with water, mixed with oxygen gas, and exposed to the action of an electrical spark, it detonates, and affords a diminution in the same way as hydrogen gas.

In one experiment with 19 cubical inches of fluoric acid gas, and ten grains and a half of potassium, 14 cubical inches of the gas disappeared, and about two and a quarter of hydrogen gas were produced. The gas had not been artificially dried; little sublimate was produced, but the whole of the bottom of the retort was covered with a brown crust. When this mass was examined with a magnifier, it seemed to consist of different kinds of matter. It did not conduct electricity; it effervesced violently in water, with the evolution of an inflammable gas, which had somewhat of the odour of phosphated hydrogen. Part of the mass heated in the air, burnt slowly, and was converted into a white saline matter. It also burnt with difficulty in heated oxygen gas, but it absorbed a portion that required nearly a red heat. The light emitted resembled that from the combustion of liver of sulphur. Chocolate coloured particles were found floating in the water, acted on by a portion of the mass, and when the solid matter was separated by the filter, the fluid was found to contain fluate of potash and potash. The solid residuum was heated in a small glass retort filled with oxygen gas; it burnt before reaching a red heat, and became white. Oxygen was absorbed, and acid matter produced. The remainder had the properties of the substance formed from fluoric acid gas, holding siliceous earth in solution by the action of water.

"The decomposition of the fluoric acid, Mr Davy observes, by potassium, seems analogous to that of the acids of sulphur and phosphorus. In neither of these cases are the pure bases, or even the bases in their common form, evolved; but new compounds result, and in one case, sulphures and sulphites, and in the other phosphures and phosphites of potash, are generated."

In another experiment Mr Davy attempted the decomposition of fluoric acid gas, which was perfectly dry, and free from siliceous earth, by mixing 100 grs. of dry boracic acid, and 200 grains of fluor spar. The mixture was introduced into the bottom of an iron tube, having a stop-cock and tube of safety attached. The tube was inserted horizontally in a forge, and 20 grains of potassium in an iron tray were placed in that part of it where the heat was only of a dull red. The bottom of the tube was raised to a white heat, and the acid, as it was generated, was acted upon by the heated potassium. The result obtained was a sublimate in some parts black, and in others of a dark brown colour. It did not effervescence with water, and when lixiviated, afforded a dark brown combustible mass which did not conduct electricity, and, when burnt in oxygen gas, afforded boracic and fluoric acids. This sublimate did not inflame spontaneously in oxyuratic acid gas; but it effervesced violently, and diffused in nitric acid. Mr Davy thinks that this substance is a compound of the olive-coloured oxide of boracium, and an oxide of the base of fluoric acid; but he had not examined its properties particularly.

Muriatic acid.—Many conjectures have been offered with regard to the nature and constitution of muriatic acid, and many attempts have been made to effect its decomposition. Mr Davy has extended his researches to this sublimate, and has prosecuted the investigation with his usual ardour. It is still, however, to be regretted, that his successes has not been commensurate with his ingenuity and industry. Some have supposed, that the base of muriatic acid is hydrogen, while others contend that the base is a compound of hydrogen and nitrogen.

The result of Mr Davy's first experiments in this inquiry showed, that the water alone in combination with the muriatic acid is decomposed, and that this elastic fluid contains a larger proportion of water than is usually supposed; and from various experiments he concludes, that muriatic acid gas, in its common state, is combined with at least one-third of its weight of water. In the prosecution of his researches, therefore, his object was to obtain the muriatic acid free from water. With this view he heated dry muriate of lime, mixed both with phosphoric acid, and dry boracic acid, in tubes of porcelain and of iron, and employed the blast of an excellent forge; but by none of these methods was any gas obtained, till a little moisture was added to the mixture, and then muriatic acid was given out in such quantity as almost to produce explosions. In distilling the liquor of Libavius, or the fuming muriate of tin, which contains dry muriatic acid, with sulphur and with phosphorus, no separation of the acid took place; but with the addition of water, muriatic acid gas was evolved with great heat and violence. By distilling mixtures of corrosive sublimate and sulphur, and of calomel and sulphur in their common states, muriatic acid gas was evolved; but when these substances were dried by a gentle heat, the quantity of gas obtained was greatly diminished. Mr Davy, and also the French chemists, endeavoured to procure dry muriatic acid by the distillation of a mixture of calomel and phosphorus. The result obtained is considered as a compound of muriatic acid, phosphorus, and oxygen. In Mr Davy's experiments, the product was more copious when corrosive sublimate was employed. With the same view of procuring dry muriatic acid gas, he exposed phosphorus to the action of oxyuratic acid gas, in the hope that in the oxidation of the phosphorus, the whole of the moisture would be absorbed; but the examination of the result showed, that no muriatic acid gas had been evolved during the process, so that the muriatic acid which had disappeared, must exist, either in the white sublimate which had collected in the top of the retort, or in a limpid fluid which had formed in its neck. When the sublimate was exposed to the air, it emitted fumes of muriatic acid, and when brought into contact with water, muriatic acid gas was evolved, and phosphoric and muriatic acids remained in solution in the water. Mr Davy regards this white sublimate as a combination of phosphoric and muriatic acids in their dry states. The limpid fluid was of a pale greenish yellow colour; it rapidly disappeared on exposure to the air, emitting dense white fumes, which had a strong smell, differing a little from that of muriatic acid. Mr Davy thinks that this is a compound of phosphoric and muriatic acids, both free from water.

Mr Davy made other experiments, for the purpose of procuring muriatic acid in its uncombined state, but with no better success. He then tried the effects of potassium introduced into the fluid generated by the action of phosphorus on corrosive sublimate; but such was the violent action of the substances operated upon, that the apparatus was generally destroyed, and he was thus precluded from examining the results. But for a particular detail of the experiments, we must refer to the memoir itself; and for the extended account of Mr Davy's investigations on this curious and interesting subject, of which we have given as comprehensive a view as our limits would permit, see Phil. Transf. 1807, 1808, and 1809.