a name given to certain substances which shine in the dark without emitting heat. By this circumstance they are distinguished from the pyrophoric, which though they take fire on being exposed to the air, are yet entirely destitute of light before this exposure.

Phosphors are divided into several kinds, known by the names of Bolognian phosphorus, Mr Canton's phosphorus, Baldwin's phosphorus, phosphorus of urine, &c., of which the last is by far the most remarkable both with respect to the quantity of light which it emits, and its property of taking fire and burning very fiercely upon being slightly heated or rubbed. For the method of preparing these, see Chemistry Index.

Besides these, however, it has been found that almost all terrestrial bodies, upon being exposed to the light, will appear luminous for a little time in the dark, metals only excepted. This points out a general division of the phosphors into two classes; namely, such as require to be exposed to the light either of the sun or of some artificial fire, before they become luminous; and such as do not. Of the former kind are the Bolognian phosphorus, Mr Canton's phosphorus, the phosphorus from earths, &c. Of the latter kind are rotten wood, the skins of fishes, and the phosphorus of urine. To these we may add some other substances which become luminous in another way; viz. the mass which remains after the distillation of volatile sal ammoniac with chalk, loaf-lugar, and the phosphorus of urine dissolved in spirit of wine. The first, which is a composition of the marine acid of the sal ammoniac with the chalk, after being fused in a crucible, becomes luminous when struck with any hard body; white sugar is luminous when grated or scraped in the dark; and the solution of phosphorus in spirit of wine is luminous only when dropped into water; and even then the light is only perceived where the drops fall into the liquid. One part of phosphorus communicates this property to 600,000 parts of spirit of wine.

There is a remarkable difference between the light of rotten wood, fishes, and that of phosphorus of urine, even when it is not in an ignited state; for this light does not cease to be luminous even when included light of wax within an exhausted receiver; the contrary of which happens to rotten wood and fishes. If air is strongly blown upon this phosphorus from a pair of bellows, it will extinguish its light for some time, which is not the case with the other kinds. When kept in water, and placed in a warm air, the phosphorus of urine discharges such large and bright flashes into the air above it, as are apt to surprise and even frighten those who are unacquainted with it. These coruscations are contracted in their passage through the water, but expand as soon as they get above it; however, the experiment can only be tried to advantage in warm weather, and in a cylindrical glass not above three quarters filled with water.

The phenomena exhibited by the earthy phosphors are very curious; both on account of the singular circumstances in which they exhibit their light, and the varieties observed in the light itself. All these, as has been already mentioned, emit no light till they have been first exposed to the light of the sun, or some other luminous body. After that, they are luminous in the dark for a considerable time; but by degrees their light dies away, and they emit no more till after another exposure to the sun. But if this happens to be too long continued, they are then irrecoverably spoiled. The same thing will happen from being too much heated without any exposure to light. Indeed, if a phosphorus, which has just ceased to be luminous, be heated, it will again emit light without any exposure to the sun; but by this its phosphoric quality is weakened, and will at last be destroyed. Indeed these phosphors are so tender, and impatient either of light or heat, that the best method of rendering them luminous occasionally is by discharging an electric bottle near them. The light of the flash immediately kindles the phosphorus, and it continues luminous for a considerable time, after which it may again be revived by another flash, and so on. However, with all the care that can be taken, these phosphors are very far from being perpetual; nor has any method been yet fallen upon to render them so.

The singularities in the light of the phosphors above-mentioned are, that they emit light of many different and most beautiful colours. This difference of colours seems to be natural to them; for some will at first emit a green, others a red, others a violet, &c. at their formation. However, the best kinds agree in this strange property, that if they are exposed to a red light, they emit a red light in the dark; and the same of other colours. But this must not be understood without limitation; nor is the phosphorescent light at any time so bright as the luminous body, whatever it was, by which it was kindled. Neither are we to imagine, that any particular phosphorus has a particu- The nature of phosphoric phenomena explained.

The explanation of the principal phenomena of phosphorus is deducible from what has been shown concerning the nature of fire, compared with what is mentioned under the article Quicklime. Under this last article it is shown, that, when calcareous earths are deprived of their fixed air, a proportionable quantity of active fire is absorbed by them; that is, the etherial fluid which pervades all bodies, has a violent tendency to expand itself, or to act all around every particle of the calcined earth, as from a centre. Of consequence, if this tendency was not counteracted by some other power, these substances would emit a perpetual flame. This power, however, is found in our atmosphere; which has already been shown either to be the positive principle of cold, or to contain it. Hence, the latent fire in these substances is checked, and cannot act, excepting within the very substance itself. But if any other body comes in contact with the calcined earth, in which the principle of cold is less vigorous than in the atmosphere, the active fire in the quicklime immediately shows itself, and the body either becomes hot, or is consumed as if by fire. Hence it will follow, that if a very inflammable body is touched by quicklime, it ought to be set on fire. But of this we have no instance, because it is impossible for the quicklime to part with any of its fire, unless it receives something in exchange. This indeed it might receive from the atmosphere; which could supply it either with more fire, if it was in a state of ignition; or with fixed air, if any substance was at hand to receive the fire. But the atmosphere refuses to part with the fire which it contains, because the effort of the fire in the quicklime is not sufficiently strong to overcome the opposition it meets with in other bodies; and, on the other hand, the effort of the fire in the quicklime is sufficient to keep the earth from attracting fixed air out of the atmosphere. But when water, for instance, is poured on the quicklime, the dry earth absorbs it very greedily, and parts with a proportionable quantity of its latent fire, which the water also absorbs much more readily than the atmosphere. Hence the mixture becomes so exceedingly hot as sometimes to fire combustible bodies. Now if, instead of water, we suppose the lime to be mixed with oil, this also will absorb the fire, but not with such force as the water; neither is the heat by any means so considerable; because oil is capable of containing a vast quantity of heat in a latent state, the only consequence of which is an increase of its fluidity, without any very perceptible change of temperature. At the same time, however, we must remember, that if the oil is in very small quantity, and intimately combined with the quicklime in that peculiar state which was formerly called phlogiston, it is easy to conceive, that it may be so much saturated with fire, as to be unable to contain any more without being ignited. In this case, if more fire is forced into the compound, a quantity of the phlogistic matter which it contains will be decomposed; and of consequence, the fire which it has imbibed will be thrown out, as in the common ignition of vapour; and in proportion to the degree of heat thus communicated, will the degree of ignition and the continuance of it be. If the quantity of heat phosphorus is very great, the phlogiston will be dissipated all at once; but if otherwise, the ignition will continue for a much greater length of time, as is the case with a common fire.

To apply this to the ascension of phosphorus, we must consider that these substances are all formed by calcining calcareous substances, and combining them different with some portion of phlogistic matter. Baldwin's phosphorus is made by dissolving chalk in the nitric acid, afterwards evaporating the solution, and driving off most of the acid. The consequence of this is, that the earth is left in an exceedingly caustic state, as the acid expels the fixed air more completely than could be done almost by any calcination whatever; at the same time that any phlogistic matter which might have been contained in the mixture is most accurately diffused through it, and combined with it. The Bolognian phosphorus is composed of a gypseous earth, which contains a quantity of vitriolic acid; and as no mineral is to be found perfectly free from phlogistic matter, the vitriolic acid unites with it during the calcination into an exceedingly inflammable sulphur; for the greater the quantity of acid there is in proportion to the phlogiston, the more inflammable is the compound*. Thus the Bolognian, as well as Baldwin's phosphorus, is a compound of quicklime and inflammable matter; and the case is still more plain with regard to Mr Canton's, where the quicklime is mixed with sulphur, and both calcined together.—Neither are the phosphorus made by calcining oyster-shells without addition to be accounted any way different from those already mentioned; since the shells always contain some portion of inflammable matter, which, being reduced to a coal by the action of the fire, furnishes a quantity of phlogiston, and imparts it to the whole of the calcareous matter.

Having thus seen that the phosphorus of which we now speak are all composed of pure calcareous earth and phlogiston, we are next to consider, that the phlogiston must be in such a state as it is when saturated with fire and ready to inflame. It is not indeed in the state of vapour, because this would require a quantity of fire detached from any other substance, and interposed between the particles of the vapour, in order to keep them at a distance, or to give it elasticity. But the fire which ought to do this is confined by the calcareous earth, which also detains the phlogiston itself. As long therefore as the balance is thus preserved, the phosphorus cannot shine; but as soon as a fresh quantity of light is discharged upon it, then more light or fire (for they are the very same in this case) enters the quicklime than it can contain. The consequence of this is, that the quantity which cannot be retained by the earth, exerts its force upon the phlogiston; which having already as much as it can hold, not only the superfluous quantity is discharged, but also part of that which the phlogiston had absorbed before. The burning indeed is very slow and weak, because the phlogiston is obstinately retained by the earth, which both impedes the ignition, and prevents the dissipation of the phlogiston in vapour. However, as soon as the lime has by its action impeded the farther extrication of the phlogiston, the balance is restored, the fire goes out, and the phosphorus ceases to be luminous. Heat, Phosphorus will kindle it again; but thus a larger quantity of phlogistic matter is dissipated, and the phosphorus is soon destroyed. Light does the same, but in a much more moderate degree; and therefore the phosphorus may be frequently rekindled by means of light, and will continue its splendor for a long time. But if the light is too long continued, or too violent, it will produce the same consequence whether it is attended with perceptible heat or not.

With regard to the phosphorus of urine, the case is the same; only, instead of the calcareous earth, we have here an acid joined with phlogiston. The latter is in exceeding small quantity, and of consequence so loaded with fire that the least additional heat, rubbing, or alteration in the weather, forces more fire upon it than it can bear, and therefore part of it is continually flashing off in those coruscations formerly mentioned. The reason why this phosphorus flashes like lightning, and the others give only a steady light like coals, is, that the compound is very volatile. It requires indeed a violent fire to distil it at first; but in the distillation so much fire is imbued, that it seems ever afterwards ready to evaporate spontaneously; and therefore phosphorus, when once made, is easily redistilled in close vessels.

It now remains only to show the reason why the phosphorus of urine and some others will shine under water, or in an exhausted receiver, while rotten wood, &c. will not. This seems to arise from the quantity of fire which they have internally, and which requires no supply from the external air, as in the case of common fire: and hence the phosphorus of urine shines more briskly in vacuo than in the air; because the pressure of the atmosphere is then taken off, and the evaporation of the phlogistic matter promoted. The light of fishes and rotten wood seems to be of an electric nature; and therefore ceases when the air is exhausted, as on this fluid all the phenomena of electricity are found to depend.

With regard to the various colours of phosphoric light, some have imagined that the earthly substance was capable of imbibing a certain quantity of light, and emitting it afterwards in the very same state, and having the same colour which it had before. But this is now known to be a mistake, and the light of the phosphorus is found to be owing to a true accension, though weak, as in other burning bodies. Hence it is very probable that the colour of the light depends upon the degree of accension; for we see that even in common fires the colour depends in a great measure on the strength of the flame. Thus the flame of a candle, where it is not well kindled at bottom, always appears blue. The flame of a small quantity of sulphur, or of spirit of wine, is blue; but if a large quantity of either of these substances be set on fire, the flame will in many places appear white. A strong flame mixed with much smoke appears red; a weak one in similar circumstances appears brown, &c.—Hence if the phosphoric is weakly kindled it will emit a brown, violet, blue, or green flame; if strongly, a red or white one.

It has already been mentioned, that almost all terrestrial bodies have a phosphoric quality: however this, in most of them, is extremely weak, and continues only for a very short time. Signor Beccaria, who discovered this property, in order to find out what substances were phosphoric and what were not, had a machine contrived like a dark lanthorn, in which he included himself, in order to perceive with the greater facility any small quantity of light which might be emitted by the substances which he designed to examine. In the side of the machine was a cylinder capable of being turned about without admitting any light. Upon this were patted the substances he designed to examine, and by turning the cylinder he immediately brought them from the light of the sun into intense darkness; in which situation there were but few substances which did not afford a sufficient quantity of light to render themselves visible. This phenomenon, however, is evidently similar to an optical illusion by which we are made to see what is not present before us; for if we look very intensely upon anything for some time, suffering no more light to enter our eyes than what is reflected from that object, we will imagine that we still see it, though we remove into the dark or shut our eyes. The reason of this is, that the nervous fluid being once put in motion after a certain manner, continues that motion for a short space of time after the moving cause is removed. In like manner, as the light is partly reflected from bodies, and partly penetrates them, when any body is exposed to the light, and then is suddenly brought into a dark place, the etherial fluid within its substance being once put into motion does not cease to move immediately, but for a time produces that vibration which we call light; for the substance of light is present in the most intense darkness as well as in sunshine. Hence almost all substances are capable of emitting light in the dark, after being exposed to a vigorous sunshine; though the reason of their doing so may be very different from that by which the phosphorus become luminous.

Many entertaining experiments may be made with other ex-

the various kinds of phosphorus, especially with that of peptins urine. This last, however, is sometimes dangerous on account of the violence with which it burns. If dissolved in oil of cloves, it loses this property, but continues to be as luminous as before; so that this mixture, called liquid phosphorus, may be used with safety. As on some occasions it may be wished to have it in powder, it is proper to observe that this may be done with safety by pouring some hot water upon the phosphorus in a glass mortar. The compound melts, and while in a soft state is easily reducible to powder of any degree of fineness.

Mr Margraff endeavoured to combine phosphorus with metals by distillation; but zinc and copper were the only two metals that showed any signs of combination (See Chemistry, No. 1413.) The great analogy, however, that has been observed between the properties of phosphorus and those of sulphur and arsenic, induced M. Pelletier long ago to suspect, that phosphorus would really combine with metals, and that the essential point was to retain the phosphorus in contact with the metal in a state of fusion. This happy idea led him to a method from which he has obtained all the success that could be desired. Of this we have already given a very contracted account after the word Phos- Phosphorus in the Index to our article Chemistry; we shall now extend that account, by giving that in the first volume of Annals of Chemistry.

"Each of the combinations which are now to be described, M. Pelletier has termed phosphorated metal.

"M. Pelletier mixed half an ounce of gold of parting, in powder, with an ounce of phosphoric glass and about a dram of powdered charcoal; he put this mixture into a crucible, covering it with a small quantity of charcoal powders; and then applied a degree of heat sufficient to melt the gold. During the operation, a considerable quantity of vapours of phosphorus was disengaged, but all the phosphorus which was produced was not dissipated; a small quantity united with the gold, which was whiter than in its natural state, broke under the hammer, and had also a crystallized appearance.

"Twenty-four grains of this phosphorated gold, placed on a cupel in a heated muffle, lost only one grain, and the button of gold that remained had the peculiar colour of that metal.

"A mixture consisting of an ounce of platina, an ounce of phosphoric glass, and a dram of powdered charcoal, being put into a crucible, and covered with a little charcoal powder, M. Pelletier gave it a degree of heat nearly equal to what would have fused gold: this he continued for an hour. Having broken the crucible, he found underneath a blackish glass a small button of a silver white, weighing more than an ounce. On the inferior part of the button were well defined crystals of the same substance, the figure of which was a perfect cube. The same experiment, frequently repeated, constantly afforded the same result.

"The phosphorated platina is very brittle, pretty hard, and strikes fire with steel; it is not acted upon by the magnet, and when it is exposed naked to a fire capable of fusing it, the phosphorus is disengaged, and burns on its surface. Exposed to the fire in a cupelling furnace on porcelain tests, the phosphorated platina leaves a black glass, which surrounds the metallic substance. The colour of the glass is owing to iron contained in the platina; and if it continue exposed to the same heat in fresh tests, the portions of glass that form latterly have not so deep a colour, are more or less greenish, have sometimes a bluish tinge, and become at last of a transparent white. This observation led M. Pelletier to imagine, that phosphorus was well adapted for separating iron from platina, and that it was one of the best means of separating it entirely from that metal. But the glass which results from the combustion of the phosphorus and its combination with the oxyd (calx) of iron, forms a crust which obstructs the combustion of the phosphorus that still remains combined with the platina. To overcome this obstacle, M. Pelletier thought of exposing the phosphorated platina to the fire, in cupels made of calcined bones, which, as they easily absorb the glass of lead, ought also to have the property of absorbing the phosphoric glass. He repeated the operation, therefore, several times successively, changing the cupel. A button of platina, which had been thus operated on four times, he presented to the academy: in this state it was capable of being reduced into plates, but was brittle when heated.

"Since the reading of his memoir, M. Pelletier has pursued his process, and has advanced so far as to be able totally to free the platina from the phosphorus, so that it may be worked when heated: thus he has procured us a method of purifying this metal more advantageous probably than any hitherto attempted. The phosphorated platina detonates strongly when it is thrown on nitre in fusion. A mixture of phosphorated platina, and oxygenated muriate of potash (dephlogisticated digestive salt), thrown into a red hot crucible, produces a brisk detonation, and the platina remains pure in the crucible.

"Half an ounce of silver, treated with an ounce of phosphoric glass and two drams of charcoal, acquired an increase of weight of one dram. The phosphorated formed was white: it appeared granulated— as it were crystallized: it broke under the hammer, but was capable of being cut with a knife. Placed in a cupel in a heated muffle, the phosphorus was disengaged, and the silver remained quite pure.

"In preparing phosphorus in the large way, M. Pelletier observed, that the phosphoric acid attacked in some degree the copper basins, which are in other respects very convenient for this operation; and in the retorts which he made use of for the distillation, he found phosphorated copper, sometimes in small distinct grains, at others in large masses, according as the degree of heat which finished the operation was more or less intense. This phosphorated he exhibited to the academy, and thence it was mentioned in the chemical nomenclature. The phosphorated of copper is also obtainable by a process similar to that which we have described for obtaining that of gold, silver, and platina. The proportions which M. Pelletier employed were an ounce of shreds of copper, an ounce of phosphoric glass, and a dram of powdered charcoal. This phosphorated appears whitish, is sometimes variegated with the different colours of the rainbow; changes on exposure to the air like pyrites, loses its lustre, and assumes a blackish hue.

"Margraff had formed phosphorated copper by distilling the oxyd of copper, called crocus veneris, with phosphorus; and M. Pelletier also obtained it by the same process: but he did not observe the property attributed to it by Margraff, of running when applied to a candle. Having placed the phosphorated in a cupel in a heated muffle, it was fused, the phosphorus inflamed on its surface; a blackish substance resembling scorce remained in the cupel, which was penetrated with a glass that gave it a blue colour.

"The phosphorated of iron produced by the fusion of an ounce of phosphoric glass, and an ounce of shreds of iron, mixed with half a dram of powdered charcoal, was very brittle, and broke white, with a striated and granulated appearance: in one cavity it was crystallized in rhomboidal prisms. It is the same substance which Bergman conceived to be a peculiar metal.

"This phosphorated, placed in a cupel in a heated muffle, soon entered into a state of fusion; in the cupel remained a brittle substance, which is an oxyd of iron, and the cupel was penetrated with a matter similar to that which M. Pelletier had observed on treating in the same manner phosphorated platina, obtained from platina not purified." "The phosphor of lead, obtained by the process already described, appears little different from common lead. It is malleable, and easily cut with a knife, but it loses its lustre sooner than lead, and when melted on charcoal by the blow-pipe, the phosphorus burns, leaving the lead behind.

"The phosphor of tin, which M. Pelletier obtained by his process, was divided into several grains, because he had not given a sufficient degree of fire to unite them. These grains did not appear different from the metal itself; but being melted with the blow-pipe, the phosphorus burnt on the surface of the metal, as in the similar experiment with lead.

"In fusing tin or lead with the charcoal powder and phosphoric glass, care must be taken not to urge the fire, as the phosphorus easily flies off from either of those metals.

"From the experiments of M. Pelletier, it appears that phosphorus may be combined with gold, platinum, silver, copper, iron, tin, and lead; and that it deprives the five former metals of their ductility. M. Pelletier proposes to make further experiments, to ascertain whether it be possible or not to combine a greater quantity of phosphorus with the two latter, and whether they will retain their malleability in that case. In another memoir he will examine the action of phosphorus on semi-metals: he proposes also to ascertain the order of its affinity with the metals and semi-metals.

"It is much to be wished that M. Pelletier may carry to perfection a work which will enrich chemistry with a species of combination hitherto almost entirely unknown, and which he has discovered means of effecting by a process equally simple and ingenious."

In the 10th volume of the same Annals we find an account of the action of lime, and of some metallic oxides on phosphorus, by Dr Raymond.

M. Gengembre discovered, that by boiling phosphorus in a solution of potash, a peculiar kind of gas was produced, which had the singular property of taking fire on coming into contact with the atmosphere, and to which the French chemists have given the appellation of phosphorized hydrogen gas. Dr Raymond thought of varying the process, in order to discover whether this gas might not be produced in some other way. He took two ounces of lime flaked in the air, a dram of phosphorus cut small, with half an ounce of water, which he mixed up into a soft paste, and put into a stone retort; to this retort a tube was fitted, the internal diameter of which, he says, ought not to exceed a line and a half, communicating with a receiver full of water. As soon as the retort was well heated, the phosphorized hydrogen gas was generated so abundantly, that, from the quantity of ingredients here mentioned, no less than three quarts of it were obtained. The residuum was found to have all the characters of the native phosphat of lime. Hence the Doctor supposes, that the water was decomposed during the process, and that its oxygen served to acidify the phosphorus; which, in this state, was combined with the lime, and formed the phosphat; while its hydrogen, assuming a gaseous state, carried with it a part of the phosphorus, to which the property of taking fire by contact with the air must be ascribed. The gas soon loses this property, and the phosphorus is condensed on the sides of the receiver: great caution, however, is necessary; for though a part of the gas may seem to have deposited its phosphorus, and to be reduced to pure hydrogen, yet another part, in the same receiver, may retain enough to cause a formidable explosion, when in contact with air.

The facility with which water was thus decomposed led the author to suspect that a similar effect might be produced by the same mixture in the mean temperature of the atmosphere. Accordingly he found that in ten days time a small quantity of hydrogen gas was generated in the vials, in which the ingredients were placed: this, however, was not phosphorized, the heat not being sufficient to volatilize the phosphorus.

Animated by this success, Dr Raymond resolved to try what could be effected by metallic oxides. He made two mixtures like the former: but instead of lime, he substituted in the one the white oxide of zinc, and in the other the black oxide of iron. After long distillation with great heat, he obtained from both phosphorized hydrogen gas: but it was produced in much less time, and in greater quantity, from the oxide of zinc than from that of iron; which he ascribes to the close affinity of the former to the phosphoric acid.

In the 12th volume of the same valuable work, we have an account of a process for making Kunkel's making phosphorus from urine, which is shorter and more economical than that by which Messrs Scheele and Ghan extract it from the bones of animals, by M. Giobert. This method is founded on the property of the metallic salts to separate the phosphoric acid from urine, which Mangraff, we believe, first discovered: but M. Giobert has greatly improved on the process directed by the German chemist, as he avoids the tedious and disagreeable operations of evaporating the urine, and exposing it to putrefaction. He tells us, that it is indifferent whether the urine be that of healthy or diseased persons; and that of horses is nearly as good for this purpose as that which is human. He gradually pours into it a solution of lead in the nitric acid, till the precipitation ceases which this had occasioned; the whole is then diluted with a considerable quantity of water, and afterward filtrated through a linen cloth. The precipitate, which is phosphat of lead, must be made up into a paste with powder of charcoal, and well dried in an iron or copper pan: it must afterward be distilled; when it will yield, first, an ammoniacal, and then an empyreumatic, oil; these oils proceed from the urine, from which it is difficult to purify the phosphat. As soon as the oil ceases to come over, a clean receiver must be applied, and the fire be greatly increased. The phosphorus generally appears in about half an hour; and, within eight hours, twelve or fourteen ounces of it may thus be obtained. If the process be conducted with care, M. Giobert thinks that a hundred parts of phosphat of lead will yield between fourteen and eighteen of phosphorus.

If on the phosphat of lead thus precipitated from urine, a solution of sulphat of ammonia be poured, and this, after digesting during twelve hours, be filtered and evaporated, phosphat of ammonia will be obtained; and if sulphat of soda be used, the result will be phosphat of soda.

Acid of Phosphorus. This acid, called also the microcosmic...