a general name for all calcareous substances when deprived of their fixed air; such as chalk, limestone, oyster-shells, &c., calcined. See CHEMISTRY, no 511, 748, 837, and 914.

Quicklime has the following properties. 1. It is entirely soluble in water, with which it unites so rapidly as to occasion considerable heat. When exposed to air, it imbibes moisture from thence. When united with as much water as is sufficient to make it a fluid paste, it is called flaked lime. Water saturated with quicklime is called lime-water. According to Brandt, lime-water contains about one part of quicklime to 700 or 800 parts of water. Slaked lime, or lime-water, being exposed to the atmosphere, attracts from thence particles of fixed air which float in it, by which means the quicklime is rendered mild, insoluble in water, and therefore appears on the surface of the lime-water, or of the flaked lime where this combination happens, in the state of mild or combined calcareous earth, convertible by a second calcination into quicklime, and is called cream of lime.

If the earth dissolved in lime-water be precipitated from thence by any substance containing fixed air, as by mild alkalis or magnesia, it will unite with this air, become mild, and resume its former weight and properties which it possessed before calcination. But if it be precipitated from the water by means of some substance quicklime, which does not contain fixable air, but which is more strongly disposed than the earth to unite with the water, for instance, spirit of wine, the earth thus precipitated will be in the state of quicklime, that is, caustic, and soluble in water.

2. Quicklime unites with acids without effervescence, which is nothing else than an extrication of the fixable air, of which quicklime has been already deprived. It nevertheless saturates as much acid as it would have done if it had not been calcined.

3. Quicklime is more powerfully disposed to unite with fixable air than fixed or volatile alkalis, or magnesia. Hence, when treated with these substances, it takes from them their fixable air, and is itself rendered mild, and restored to its original weight and properties. Thus two drams of chalk, having been by calcination reduced to one dram and eight grains of quicklime, were thrown into a filtrated solution of an ounce of mild fixed alkali in two ounces of water, and digested during some time; by which the calcareous earth became mild, and weighed one dram and 58 gr. By means of magnesia, the calcareous earth may be precipitated from lime-water; and this earth is found to be mild, and to have deprived the magnesia of its fixable air. By depriving alkalis of their fixable air, quicklime renders them more caustic and solvent, for the same reason that itself is by this privation of air rendered more caustic and powerfully solvent. This increase of causticity and dissolving power is consistent with a general rule, namely, that the more simple or less compounded any body is, that is, the less its general tendency to union is satisfied, the more disposed it is to unite with or dissolve other substances.

4. Quicklime has a disposition to unite with sulphur, with which it forms a heap of sulphur, similar to that made by sulphur united with an alkali, and, like this, soluble in water. It is also disposed to unite with oils and with animal and vegetable matters, with respect to which it discovers a caustic and corrosive property.

5. Quicklime mixed with sand forms a mass which hardens, and is used as a cement or mortar.

All these properties of quicklime have been the objects of consideration to the chemists and philosophers; who have, as usual, been divided in their opinions on the subject. The evident resemblance of the action of quicklime to fire, has given occasion for one party to derive all the active properties of this substance from fire; while, on the other hand, its want of heat, and incapacity of setting bodies on fire, unless by an accession of water, were objections altogether infirmountable. On the other hand, those who denied the materiality of fire, and affirmed that it consists only in a motion mechanically produced among the particles of bodies, were altogether at a loss to show a reason why this motion, or any thing resembling it, should continue perhaps for months after the exciting cause is taken away. To remove this difficulty, some have had recourse to the action of a latent acid communicated to the quicklime by the fire; and which one chemist (Mr Meyer) has distinguished by the name of acium pingue. But on this hypothesis it may be remarked in the first place, that the action of acids is as difficult to be explained as that of fire; and, in the second place, that as all substances, by calcination into quicklime, lose considerably of their weight, Quicklime, weight, it seems very improbable that they should acquire an acid or any other substance which could increase their weight. Besides, from the experiments of Dr Black, it appears that the diminution of weight in calcareous substances is owing to their parting with a quantity of fixed air, the weight of which is much more considerable than that of any moisture or fatty matter they contain. The loss of this fixed air is now also universally allowed to be the reason of the causticity of the quicklime, as its superior attraction for fixed air is looked upon to be the reason why it renders fixed and volatile alkalis caustic like itself. The only question therefore can be, By what means are the calcareous earths deprived of their fixed air? To this question the answer is evident, namely, that the action of the fire expels the fixed air; and if this is the case, it is evident, that to this action of fire, continued, the caustic properties of the lime are owing.

We come now to the discussion of the question, Whether quicklime is to be considered as a pure earth, or a combination of it with something else?—Most of the chemists, since the discovery of fixed air, have been inclined to think that quicklime is a pure earth uncombined with anything else, and that it approaches more nearly to the state of elementary earth than any other. But this opinion seems not to have a solid foundation; for there are other earths, such as the basis of alum, which, as far as they can be examined by us, are equally pure with quicklime, and yet discover not the smallest causticity, even after the most violent calcination. Besides, from the property which quicklime has of depriving alkaline salts of their fixed air, we may learn, that there exists in it, when kept by itself, a certain principle which prevents it from absorbing again the fixed air, with which it was once so closely united, except in certain circumstances. It is well known, that fixed alkalis, as well as those which are volatile, will absorb fixed air from the common atmosphere; and hence, that they are prepared in the most caustic state, they will in a very short time become mild by an exposure to the atmosphere; nay, it requires no small degree of care to prevent the atmosphere from having as much access to them as is necessary to change them from a caustic to a mild state. Now, these substances thus attract the fixed air from the atmosphere, it thence appears that the atmosphere parts very readily with the fixed air which it contains. The quicklime, however, though it has a greater attraction for fixed air than the alkalis, yet does not become near too soon mild from exposure to the air as the alkalis which have less attraction than itself. Hence the necessary inference must be, that quicklime, after being once calcined, instead of attracting, repels fixed air, unless it is placed in certain circumstances, wherein the repelling power is destroyed, and the attractive power again manifests itself. Now it is manifest, that the power which originally repelled the fixed air was the action of fire; and consequently, while the quicklime refuses to attract fixed air, we must conclude that it is the same action which prevents the union. Quicklime therefore is not a pure earth, but a combination of a pure earth with fire; just as chalk, or limestone uncalcined, is not a pure earth, but a combination of a pure earth with fixed air. In all chemical trials, then, where quicklime is used, the double elective attraction will manifest itself as much as in a combination of different salts, metals, and acids. Thus quicklime, when water is poured on quicklime, the attraction between that element and earth is stronger than the attraction between earth and fire. The consequence is, that the water expels the fire, just as vitriolic acid poured upon sea-salt expels the marine acid. The fire, then, having nothing with which it can form a chemical combination, becomes sensible to the touch, first making the lime very hot, and then gradually dissolving in the atmosphere. However, as the water combines with the earth but in very small quantity, it can only expel the fire from that quantity with which it does combine; and consequently the lime still retains its caustic quality, though in a degree somewhat milder than what it was originally. We must also consider, that water itself has a considerable attraction for fire as well as for earth; and the consequence of this must be, that part of the lime will be dissolved in the water, if more of that element is added than what the earth can absorb without losing the form of a dry powder. Hence the origin of lime-water, which is only a small quantity of lime in its caustic state dissolved in a large quantity of water. This dissolution is owing to the double attraction of fire to earth and water; for as long as the water can admit the calcined earth to that intimate union with itself which is called a chemical combination, the earth must still retain all the causticity which the fire gives it, and dissolve in the water. When the earth is in too large quantity to be thus combined with the water, the latter is only absorbed into the pores of the earth, where by its bulk it splits the stone or calcined matter all to pieces, and reduces it to an impalpable powder, expelling a proportionable quantity of fire from those pores which it now occupies. The water, however, is capable of radically dissolving but a very small portion of calcined earth; and therefore the same quantity of quicklime will serve for preparing lime-water a great number of times over; but at last a large quantity is left, which seems to be quite inert, and has lost the properties of quicklime. Those who have tried the experiment of lixiviating lime with fresh quantities of water till it ceases to be soluble, have fixed the proportion of soluble matter in the lime at about one-third of the whole; but from Dr Black's experiments it appears that quicklime may all be dissolved in water at once, provided the water is in sufficient quantity. Its inactivity, therefore, after repeated affusions of water, must be owing to some change produced by the water; but whether this is owing to an absorption of all the fire it contained by the great quantity of water, or to a supply of fixed air given by the water, has not yet been determined by any experiment.

If, instead of pouring cold water upon quicklime, we pour that which is already heated, the absorption is much less complete; because the water, having already a superfluous quantity of heat, is resisted by that which is contained in the quicklime in a latent state; and hence it is a general observation, that hot water is less proper for slaking lime than cold. But if we pour on any acid upon quicklime which contains a great quantity of fire in a latent state, and has likewise a violent attraction for the earth, a much greater degree of heat is produced than with simple water. With the vitriolic acid, indeed, this is not so well perceived, if the com- Quicklime, when calcareous earths are made use of; because their insolubility in this acid diminishes its effect: but if, instead of these earths, we take magnesia newly calcined, the heat is so great, that the aqueous vapour, not having time to evaporate slowly, is driven off with a considerable explosion. If the common calcareous earths, well calcined, are dissolved in the nitrous acid, a most violent degree of heat is produced; more indeed than in any other case where a liquid is concerned; for the nitrous acid itself contains a great deal of latent heat; the quicklime does the same; and by the intimate union of the earth with the acid, all this latent heat, at least a great part of it, both in the quicklime and spirit of nitre, is displaced, and attacks the aqueous fluid, as being nearest to it; from whence it is dissipated in the air, or absorbed by the neighbouring substances. The same thing happens, only in a less degree, when the marine acid is employed.

When quicklime is mixed with a solution of mild alkali, a double decomposition, and two new compositions, take place. The quicklime may be considered as a combination of earth and fire, while the alkali in the present case acts as a combination of salt and air. These two substances, therefore, are no sooner put into such circumstances as enable them to act on each other, than the quicklime attracts the air from the alkali, and gives its own fire in exchange, which the alkali takes up, and thus is rendered caustic, while the quicklime becomes mild. Nevertheless, though the alkali here seems to have the greater attraction for fire, and the quicklime for air; yet it appears that the alkali is by no means capable of keeping the fire which it has imbibed for any length of time: for no sooner is it exposed to the action of the air, than it parts with the fire which it had imbibed, regains its air, and becomes mild. This, however, in all probability is owing to its extreme solubility in water while in a caustic state; for quicklime itself, when dissolved in water, very easily regains its fixed air, nay, even more than it contains in a natural state. See the article Salt.

On the whole, then, the properties of quicklime may be explained in a very easy manner on Dr Black's principle of latent heat. That heat consists in a latent state in quicklime, as well as in vapour, we have incontrovertible proofs; because, in all cases where quicklime changes its nature and becomes more mild, a degree of heat is produced, and which is always proportionate to the change made on the quicklime. In the making of quicklime, therefore, the air is expelled, and a proportional quantity of fire enters; in dissolving it in an acid, flaking, &c., an acid, air, or water, expels part of the heat, which then becomes sensible. By long exposure to the air, the heat gradually evaporates; the fixed air resumes its place; and the quicklime being thus increased in bulk, embraces those bodies very closely which lie nearest to it; insomuch that, when mixed with sand and stones, it will harden with them almost into the solidity of a rock (see Cement and Mortar). When mixed with animal or vegetable substances, it destroys or decomposes them, both by the action of its internal heat, and by its attraction for a certain acid contained in the animal substances, and an oily matter in the vegetables; and hence its property of burning cloth, though its attraction for the oily matter just mentioned makes it an excellent whitener when properly applied. See Bleaching.

Quicksilver, or mercury, one of the perfect metals, and so fusible that it cannot be reduced to a solid state but by the most intense degree of cold, scarcely, if at all, under 40° below 0 of Fahrenheit's thermometer. See Congelation. For the method of extracting quicksilver from its ore, &c., see Metallurgy, p. 454, and 475. For the various preparations, &c., from it, see Chemistry Index at mercury and quicksilver, and Pharmacy Index at mercury and quicksilver. And for its use in medicine, see Medicine, no. 350, and Mercury.

It is found, 1. Native, as in the mines of India, Friuli, Lower Austria, Deux Ponts, &c., flowing through beds of stone, and collecting in the cliffs or cavities of rocks. In these mines, however, Mr Kirwan is of opinion that it is mixed with some other metal, as the globules into which it is divided are not perfectly spherical. In Sweden and Germany it has been found united to silver in form of a hard and somewhat brittle amalgam. It has also been observed visibly diffused through masses of clay or stone, of a white, red, or blue colour, and very heavy in Spain and Idria; and in Sicily in beds of chalk.

Mines of quicksilver, however, are very rare, inasmuch that, according to the calculations of Hoffman, there is 50 times more gold got every year out of the mines than mercury and its ores. But Dr Lewis, in his notes upon Newmann, says, that Cramer supposes that Hoffman only meant five times instead of 50; but neither the Latin nor the English edition of this author expresses any such thought; on the contrary, he adopts the same opinion; and only adds, that mercury is much more frequently met with than is commonly believed; but being so volatile in the fire, it often flies off in the roasting of ores, and escapes the attention of metallurgists.

According to Newmann, the mines of Idria have produced at the rate of 231,778 pounds weight of mercury per annum; but those of Almaden in Spain produce much more. The chemists of Dijon inform us, that their annual produce is five or six thousand quintals, or between five and six hundred thousand pounds weight. In the year 1717 there were upwards of 2,500,000 pounds of quicksilver sent from them to Mexico, for the amalgamation of the gold and silver ores of that country.

At Guacanvelica in Brazil the annual produce of the mines, according to Bomare, amounts to one million of pounds, which are carried overland to Lima, thence to Arica, and lastly to Potosi for the same purpose.

Besides these mines there are others in Brazil near Villa-Rica, where such a quantity of cinnabar and native running mercury are found near the surface of the earth, that the black slaves often collect it in good quantities, and sell it for a trifling price to the apothecaries; but none of these mines have ever been worked or taken notice of by the owners. Gold naturally amalgamated with mercury is likewise met with in the neighbourhood of that place; and it is said that almost all the gold mines of that country are worked out by simply washing them out with running water, after reducing into powder the hard ores, which are sometimes imbedded in quartzose and rocky matrices.

In the duchy of Deux Ponts and in the Lower Austria Aria the quicksilver flows from a schistose or stony matrice, and is probably, says Mr Kirwan, mixed with some other metal, as its globules are not perfectly spherical. The mines of Friuli are all in similar beds or strata. The metal is likewise found visibly diffused through masses of clay or very heavy stone, of a white, red, or blue colour; of which last kind are the mines of Spain, some of Idria, and of Sicily. Macfagni found fluid quicksilver, as well as native cinnabar and mineral ethiops, near the lake of Travele in the duchy of Sienna; but the quantity was so small as not to be worth the expense of working. On the other hand, the following mines afford profits to the owners after clearing all expenses, viz. those at Kremnitz in Hungary; at Horowitz in Bohemia; Zorge in Saxony; Wolfitein, Stahlberg, and Moefeld in the Palatinate. Mercury is also brought from Japan in the East Indies; but the greatest part of what is sold in Europe as Japan cinnabar is said to be manufactured in Holland.

Lemery, Pomet, and others, lay down some external marks by which we may distinguish those places where there are mines of quicksilver, viz. thick vapours like clouds arising in the months of April and May; the plants being much larger and greener than in other places; the trees seldom bearing flowers or fruit, and putting forth their leaves more slowly than in other places; but, according to Neumann, these marks are far from being certain. They are not met with in all places where there is quicksilver, and are observed in places where there is none. Abundance of these cloudy exhalations are met with in the Hartz forest in Germany; though no mercury has ever been found there; to which we may add, that though vast quantities of mercurial ores are found at Almaden in Spain, none of the above-mentioned indications are there to be met with.

Native mercury was formerly sought from the mines of Idria with great avidity by the alchemists for the purpose of making gold; and others have showed as ridiculous an attachment to the Hungarian cinnabar, supposing it to be impregnated with gold; nay, we are informed by Neumann, that not only the cinnabar, antimony, and copper of Hungary, but even the vine trees of that country were thought to be impregnated with the precious metal. Not many years ago a French chemist advertised that he had obtained a considerable quantity of gold from the ashes of vine twigs and stems, as well as of the garden soil where they grew; but the falsehood of these assertions was demonstrated by the count de Lauragais to the satisfaction of the Royal Academy of Sciences.

The reduction of mercury into a solid state, so that it might be employed like silver, was another favourite alchemical pursuit. But all processes and operations of this kind, says Neumann, if they have mercury in them, are no other than hard amalgams. When melted lead or tin are just becoming consistent after fusion, if a stick be thrust into the metal, and the hole filled with quicksilver, as soon as the whole is cold, the mercury is found solid. Macquer informs us, that mercury becomes equally solid by being exposed to the fumes of lead. Maurice Hoffman, as quoted by Neumann, even gives a process for reducing mercury, thus coagulated, to a state of malleability, viz. by repeatedly melting and quenching it in linseed oil. Thus, he tells us, we obtain a metal which can be formed into rings and other utensils. But here the mercury is entirely dissipated by the repeated fusions, and nothing but the original lead is left. Wallerius, after mentioning strong soap-leys, or caustic lixivium, and some other liquors proper for fixing quicksilver, tells us, that by means of a certain gradatory water, the composition of which he learned from Creuling de Aureo Vellere, he could make a coagulum of mercury whenever he pleased, of such consistency that great part of it would resist cupellation; but what this gradatory water was, he has not thought proper to lay before the public.

2. Native precipitate perfs, in which the metal is mineralized by aerial acid. This was lately found in Idria, in hard compact masses of a brownish red colour and granular texture, mixed with some globules of native mercury. An hundred parts of it afford 91 of running mercury.

Various little globules of mercury were contained in this ore, which are rendered very visible by being heated, but are soon reabsorbed by cooling. On exposing it to the fire in an iron spoon, the red colour soon became more vivid, but turned yellowish on cooling. Distilled in a pneumatic apparatus, a quantity of dephlogisticated air was produced, though less by one fourth than what should have been produced by an equal quantity of cinnabar. On distilling an ounce of this ore in a glass retort, a little yellow powder was left, which weighed a fourth part of a grain, and stained the bottom of the retort in a manner similar to what is done by the calx of silver to white glass in similar circumstances. On cupelling this powder with 144 grains of lead wrapped up in paper, the increased weight of the lead over that of the test of comparison showed that the calx was reduced into its metallic state of silver and mixed with that of lead.

3. Mineralized by the vitriolic and marine acids. This kind of ore was first discovered in the year 1776, at Obermofchel in the duchy of Deux Ponts. It has a spar-like appearance, and is either bright and white, or yellow or black, and mixed with cinnabar in a stony matrix. The native marine salt of mercury is in the state of corrosive sublimate.

4. Native cinnabar, in which the metal is mineralized by sulphur. This is of different shades from a yellowish to a deep red; and is found either pure in hard friable masses, either shapeless or crystallized in cubes, and sometimes transparent, or intermixed with clay or stone, or interspersed through the ores of other metals, particularly those of silver, copper, or martial pyrites. Its texture is either radiated, striated, scaly, or granular. An hundred parts of cinnabar contain about 80 of mercury and 20 of sulphur; but artificial cinnabar contains a little more sulphur, and hence its colour is darker. Its specific gravity is about 7.000; it sublimes in close vessels, and is decomposed and volatilized in open ones. It is found in the duchy of Deux Ponts, in the Palatinate, in Hungary, Friuli, and Almaden in Spain, and in South America, especially at Guanacavelica in Peru. It is sometimes compact, and sometimes found in transparent, ruby-coloured crystals, and often in a kind of scales or flattened laminae. It is called native vermilion, and cinnabar in flowers, when it is in the form of a very bright red powder. It is also found in different earths, in selenite mixed with iron, with pyrites, and with sulphur. Mr Foucroy enumerates the following varieties: 1. Transparent cinnabar, red and crystallized in very short triangular prisms, terminated by triangular pyramids. 2. Transparent red cinnabar, in octohedral crystals, consisting of two triangular pyramids united at their bases and truncated. 3. Solid compact cinnabar, of a brown or bright red; it is sometimes foliated. 4. Red cinnabar distributed in flake, on a flothy matrix, or on solid cinnabar. It is sometimes composed of needles like cobalt. 5. Cinnabar in flowers, or native vermilion. It is of a bright red colour, and satiny appearance, adhering to different matrices, in form of a very fine powder. It is sometimes crystallized in very small needles, and then greatly resembles the foregoing.

The finer coloured ores of mercury are never worked for extracting the metal, but used entirely as pigments; but they have been very injudiciously preferred for medicinal uses to the more pure factitious cinnabars; for we seldom meet with any native cinnabar that has not some earthy or tony matter intermixed with it, nor with two pieces that perfectly agree. There are three varieties principally distinguished in the shops; viz. 1. Cinnabar in masses weighing from one to six ounces or more. 2. In grains, prepared by breaking the worst coloured masses, and picking out the best coloured bits. 3. Washed cinnabar, prepared by washing over the lighter impurities that are to be found in it. No native cinnabar should ever be employed in medicine without being previously purified by sublimation. Neumann informs us that he never met with any native cinnabar which did not leave a grey ash or sand, amounting, among different parcels, from one ninth to one fifth of the mineral employed. The residuum had no gold in it, though the colour of its solution and precipitate gave some expectation of it at first sight.

Neumann remarks, that though vitriolic acid forms with mercury a lively yellow concrete, viz. turbith mineral, and with the inflammable principle a yellow sulphur; and though sulphur itself forms with mercury a beautiful red cinnabar; yet the same vitriolic acid destroys the red colour entirely, rendering it as white as milk. This change is not immediately produced on common cinnabar by the vitriolic acid; but, on being digested over a strong sand heat in a glass cup, it soon becomes as white as cream; and the vitriolic acid takes the form of a strong sulphureous and volatile vapour, very suffocating and corrosive; emitting very piercing fumes for some time, which turned the paper that covered it black, and destroyed its texture.

5. Black ore of mercury, in which the metal is mineralized by sulphur and copper. This is of a blackish grey colour, a glaify texture, brittle, heavy, and decrepitating strongly when heated. It is found at Muffel Landberg. An ore of this kind is also found in the duchy of Deux Ponts. In the sulphur of Idria a black cinnabar is likewise said to be found, which retains its colour in sublimation; but this is not yet sufficiently confirmed, though it is too bold an assertion of Dr J. R. Forster that no such cinnabar has ever been found. He adds, that a certain learned man thought he had discovered some near the copper ores at Lauterberg; but that it proved to be a red copper salt, which is still to be met with in that place.

6. Pyritous mercurial ore was brought from Dau- phiny by Mr Montigny in 1768. It is grey, whitish, and friable. An hundred parts yielded one of mercury, one half of silver, the remainder being iron, cobalt, sulphur, and arsenic.

7. An ore of mercury, in which the metal is mineralized with iron by sulphur, is mentioned by Sir Torben Bergman in his Scandia, sect. 177. He says that it is doubtful whether this does not belong to the species of cinnabar, as the iron is perhaps only mechanically diffused thereon. Mr Mongez informs us, that there are but few instances of cinnabar in which iron is not found in its calcined form, though, in the act of the ore being reduced, it passes to its metallic state, and becomes capable of being acted upon by the loadstone.

Another pyritous ore of cinnabar was found at Me- nidot, near St. Lo in Lower Normandy. It consisted of differently sized grains of a red brown colour: they had a vitriolic taste and sulphureous smell. Pyritous ores of this kind are likewise found at Almaden in Spain, and at Stahlberg in the Palatinate. The cinnabaric pyrites of this last place are of a dodecaedral form.

8. Mr Gellert informs us, that an ore of quicksilver is met with in Idria, where the mercury lies in an earth or stone, as if it were in a dead form; and has the appearance of a red-brown iron-stone, but much heavier. It contains from three quarters to seven-eighths of the purest mercury, leaving after distillation a very black strong earth, giving also some marks of cinnabar. For, as we do not know the ultimate divisibility of mercury, we cannot justly determine the point of its fluidity, although its globules may be no more differ- entible.

The river-ore, which is most common in Idria, and has its name from its colour, resembles an indurated iron-clay; but its weight discovers it to have metallic contents. An hundred weight of it sometimes yields 80 pounds of quicksilver.

The brand-ore, or burning ore of the Germans, likewise belongs to this species. It may be lighted at a candle, and yields from 9 to 50 pounds of metal in the 100.

9. Dr Gmelin informs us, that cinnabar mixed with arsenic or realgar is said to be found in Japan; and that at Morshild the cinnabar and white calx of arsenic present themselves in the same rock.

10. Besides the ores already mentioned, we sometimes meet with quicksilver natively amalgamated with gold, silver, and other metals. This is taken notice of by Bergman; and from the authorities of Monet and Prof. Gmelin, Mr Kirwan informs us, that in Sweden and Germany this metal has been found united to silver in an hard and brittle amalgam. M. de L'Isle had a specimen of this ore from Germany; which, as M. Mongez informs us, is imbedded in a quartzose mass, and mixed with cinnabar. A specimen brought from the mine called Carolina, in a crystalline form, was deposited in the royal cabinet at the king's garden at Paris. M. de L'Isle likewise informs us, that a specimen of native gold was brought from Hungary, which, according to Countiedt, was probably an amalgam of mercury and gold. It is composed of quadrangular prisms, of a greyish yellow colour, and brittle texture. Neumann likewise observes, that sometimes a mineral, containing... containing gold or silver, is met with among mercurial ores, though very rarely.

These natural amalgams account for the great specific gravity of some kinds of quicksilver. This may proceed from a natural mixture of gold, though, according to Boerhaave, it may also arise from its being redistilled a great number of times. By a similar mode of reasoning we may conclude, that the smaller specific gravities of quicksilver proceed from its amalgamation with silver, lead, and other metals or semimetals, which in spite of repeated distillations may still preserve their union with it; for Dr Boerhaave informs us that he could not, by any number of distillations, free mercury perfectly either from tin or lead.

M. Magellan, in his notes on Cronstedt's Mineralogy, says, "That mercury is many times found amalgamated with lead, is easily evinced by the process of M. Groffe mentioned by Macquer in his Elements of Chemistry, where the method of extracting mercury from some solutions of lead is described; but the same Macquer, in his Chemical Dictionary, positively affirms, that, though Beecher and Knebel have both given other processes for extracting mercury from lead, and though the method pointed out by M. Groffe is easier than the others, nevertheless it does not succeed if the lead be quite pure without any amalgamation with mercury. And Boerhaave has expressly made the same assertion, complaining of those authors who affirm the contrary."

Dr Black, however, seems to be of a different opinion; and, in his public course of lectures, teaches that, "by some processes of the more difficult kind, mercury may be extracted from lead;" though he cautions us, at the same time, not to infer from this, or any other chemical process, the possibility of the transmutation of metals.

Mercury is not in any way altered by the action of light. Its dilatation by heat is extremely regular, as has lately been shown, in a very great variety of experiments, by Dr Adair Crawford; for which reason it is used as the measure of heat, and thermometers are usually filled with this metal. When opposed to the heat of about 600° of Fahrenheit, it boils and is dispersed in an invisible fume; which, however, has been observed to have the elasticity of the steam of water, and to burst an iron box in which it was attempted to confine it. If it be made to boil in a close vessel fitted with a proper apparatus, it will all come over in its proper form, and leave any fixed matter it might contain in the retort. This affords an easy method of purifying it from the base metals with which it is frequently adulterated; though even in this way it is necessary to raise the fire cautiously, or a part of the fixed metal will be carried up along with the mercury. And even with all the care that can be taken, it has been found impossible, as has been already said, to free it perfectly from a mixture of the base metals by any number of distillations.

By a very great number of distillations, however, it was said that some change might be made upon this metal; and that it became not only purer, but specifically heavier, by such an operation. Boerhaave, after making it undergo this operation 511 times, found some difference; but three years after, in a Memoir inserted in the Philosophical Transactions for 1736, he acknowledged, that, on repeating the operation 877 times, its specific gravity, as shown by Dr Gravefande's nice hydrostatic balance, appeared to be no more than 13,500 to distilled water.

Boerhaave died (says Mr Magellan in his Notes on Cronstedt's Mineralogy) two years after, on the 23rd of September 1738; and left his papers to his two nephews, Herman, who died the 7th of October 1753, and Kaw, who died five years after. On their deaths the manuscripts fell into the hands of Charles Frederick Krute physician to the Emperor of Russia. This gentleman published a short extract from Boerhaave's Diary in the ninth volume of the Novi Commentarii of the Imperial Academy of Petersburgh, of which the following are the results.

"The specific gravity of the purest gold to that of distilled water is

| Distillation | Specific Gravity | |--------------|-----------------| | Once | 19,024 | | Distilled 1009 times | 13,570 | | Once from its amalgam with gold | 13,550 | | 750 times from the same amalgam | 13,520 | | 877 times from the same | 13,500 | | Once from its amalgam with silver | 13,550 | | 217 times from the same amalgam | 13,500 |

It is evident, therefore, by these facts, that mercury does not acquire any additional increase to its specific gravity by the mere repetition of simple distillations, nor by its amalgamations with gold or silver, provided it be afterwards properly separated by fire."

It is certain, however, that there are very considerable differences in the specific gravity of different specimens of quicksilver; and authors have by no means agreed in fixing the standard.—Bergman states it at 14,110; and Mutschelbroek affirms that such was the specific gravity of Boerhaave's quicksilver that had been distilled 511 times; but some modern authors, among whom is M. Fourcroy, state the specific gravity of this metal at no more than 13,000. Modern experiments, however, show that it is generally about 13,500 or 13,600. "This (says Mr Magellan) I am informed was the mean specific gravity found by the late Lord Cavendish, after the repeated and nice trials he made upon 50 different specimens of quicksilver, on which he employed all his industry and attention to determine this point.

"The hydrostatic experiments I lately undertook of this kind upon ten different specimens of mercury, two of which were revived from natural and artificial cinabar by the operator of Mr Kirwan, confirmed me in the same opinion.

"The temperature of the atmosphere was nearly the mean, viz. at the 50th degree of Fahrenheit's thermometer; and the scales employed were so nice, that they turned with the hundredth part of a grain when loaded with four pounds weight.—The method made use of to ascertain these specific gravities is the easiest of all. A phial of white glass with a ground stopple was counterbalanced with lead or other matter in a nice pair of scales. The substance to be tried was introduced into the phial and weighed together, and the weight we suppose = a. The remaining space of the phial being then filled with distilled water, we suppose the weight now to be = b. Lastly, the phial was filled with distilled water, and the weight supposed = c. It is evi-

[Continued on next page] dent, that \( b - a = d \), the quantity of water in the second operation; \( c - d = e \), the water whose bulk is equal to that of the substance; and that \( \frac{a}{c} \) is the specific gravity sought for.—Particular care was taken that no bubble of air remained in the inside. For this purpose a very small groove was made with a file on the inside of the glass stopper; and this was introduced likewise without admitting any air, leaving the superfluous water to rush out.

"The greatest specific gravity of any of those specimens was 13.620, and the least 13.450. The heaviest was neither of the two that had been distilled from cinabar, but a common quicksilver bought at Apothecaries Hall, London; and the lightest was taken from a barometer of the best and dearest kind made by one of the most reputed instrument-makers in England.

"The most obvious cause of this difference of specific gravity in quicksilver seems to be its mixture or amalgamation with other metals. Certainly, when united to gold, its gravity must of course be specifically augmented: on the contrary, it must be lessened when united with any other metal, platinum only excepted; and the same must be the case whether water or any other moisture is mixed with it; for in such a case the metal will be found heavier after evaporation. A simple boiling of the quicksilver over the fire in an open vessel will completely free it from this mixture; and no careful maker of experiments should neglect the preparation before he undertakes to employ mercury in any process, or for any purpose of the philosophical kind. The boiling must be continued for 20 or 30 minutes in order to expel the whole moisture.

Another cause by which the specific gravity of quicksilver becomes subject to alteration is the difference of temperature of the atmosphere at the time of making the experiment. Nor is it quicksilver alone, but every other substance whose specific gravity is affected by this cause in a greater or lesser degree; insomuch that Mr Magellan does not hesitate to pronounce the labours of all those who have undertaken to compose tables of specific gravities, without regard to this circumstance, to be, if not entirely useless, at least incapable of affording proper satisfaction in the nice inquiries that depend on this knowledge.

In Eifenehrn's table of specific gravities it is asserted, that a cubic inch of mercury in summer weighs seven ounces, one gros, 66 grains; but in winter it weighs 20 grains more; the whole weight then being seven ounces, two gros, 14 grains (allowing 72 grains to the gros). This, however, leaves the matter almost in as great uncertainty as before; the summer and winter temperature being widely different in different places, and very often even in the same place. Unless therefore the temperature of the air is attended to at every experiment in taking the specific gravity of any substance whatever, there can be no certainty of the result.

Quicksilver always feels cold when touched in the common temperature of the atmosphere. Our sensations, according to Fourcroy, deceive us in this case, for a thermometer dipped in quicksilver always shows the common temperature. "The great continuity of contact between the live skin and numerous metallic particles in an equal space, and which are proportional to its great specific gravity, necessarily produces a strong sensation of its own temperature, this being always much less than that of a living body; and the multiplicity of these points of contact being all at once applied to this organ of sensation, must be more powerfully felt than whenever we touch any other matter that is lighter in itself, or of a less density."

Notwithstanding this apparent coldness, however, quicksilver, when exposed to the same degree of heat, and in the same circumstances with various other substances, soon becomes hotter to the touch than any of them. "The fundamental principle of this (says Mr Magellan) consists in the small quantity of specific fire, or the least capacity which mercury is endowed with of receiving heat. This is such, that, compared with the capacity of water for the same purpose, it is in the ratio of 0.033 to 100, as appears by the table of the quantities of specific fire contained in various bodies.—This table, published in Magellan's Essay on Elementary Fire, was grounded upon various important experiments and observations made by Mr Kirwan, in consequence of the new Theory of Fire discovered by Dr Crawford. Hence it follows, that if equal quantities of heat be communicated to equal quantities of water and mercury, the latter will have a temperature 30 times greater than that of the water; that is to say, in the inverse ratio of their respective capacities, or as 1 to 30 (=0.033 : 1.000), in the same manner as it must happen, when equal measures of corn or any fluid are thrown into vessels whose bottoms are as 30 to 1; for then their heights must necessarily be in their inverse ratio, viz. of 1 to 30, &c. See Chemistry, no 1225, &c.

Quicksilver does not appear to dissolve in water; but Fourcroy remarks, that physicians are in the practice of suspending a bag full of it in vermifuge pills during their ebullition, and that experience has evinced the good effects of it. Lemerdy affirms, that in this process there is no loss of weight; but this is denied by others. Fourcroy affirms, that this metal, rubbed between the fingers, emits a perceptible odour, though Magellan says he tried the experiment many times without success.

Fourcroy likewise affirms, that mercury when pure emits a phosphoric light by agitation, particularly in hot seasons. This phenomenon has certainly been observed in the mercury of the barometer; but its appearance on other occasions rests entirely on the authority of Mr Fourcroy. Even in the barometer it does not take place, unless the Torricellian vacuum be not perfectly made in the space at the top of the tube. Phials of glass nearly exhausted of air, and containing some quicksilver hermetically sealed up, will, on being shaken, produce as much light in the dark as is sufficient to show the hour on the dial-plate of a watch. But if a perfect vacuum be produced by nicely boiling the quicksilver within the glass, no appearance of this kind is to be perceived. The phenomenon is certainly of the electrical kind; and its not appearing in the perfect vacuum is owing to the difficulty there is in setting in motion any large quantity of electric matter by itself, which indeed can scarce be done without producing very violent effects. See Electricity-Index.

Mercury unites with all the metals and semimetals, excepting iron and regulus of antimony. These compounds are called amalgams; and Mr Machy has observed, served, that in forming them a certain degree of cold is produced. He made the experiment by covering the ball of a thermometer with tin-foil, and then dipping it into quicksilver; upon which that in the thermometer fell some degrees; which agrees perfectly well with the doctrine of latent heat first discovered by Dr Black, as it shows that in this, as well as other cases, where a body passes from a solid into a fluid state, a degree of cold is produced.—The following observations on the amalgams of mercury with different metals are extracted from the Memoirs of the Academicians of Dijon.

1. The amalgam of gold and mercury crystallizes into quadrangular pyramids. Six ounces of mercury are retained by one of gold in this crystallization; but that with silver retains a third part more of quicksilver.

2. The amalgam with silver is likewise susceptible of crystallization, and assumes the form of a tree; every ounce of silver retaining eight of mercury. This amalgam, by means of the nitrous acid, well freed from the vitriolic solution of silver in the same, forms that curious kind of vegetation mentioned in the article Chemistry, no 754, called Arbor Diana, or Arbor Philosophorum.—The following is recommended by Mr Magellan as the shortest process:

"Diffuse 238 grains of silver, and half as much quicksilver, in pure nitrous acid. Add to the solution, when made, five ounces (of 576 grains each) of distilled water. Put this solution into a spherical vessel of white glass, at the bottom of which must already be put 432 grains of an amalgam of silver of the confluence of butter: let the vessel be kept in a quiet place, free from any shaking or external agitation; and at the end of some few hours the figure of a bush or tree of silver will be formed within the water of the glass vessel. The metals contained in the solution and in the amalgam attract each other, and a number of small tetrahedral crystals are formed, which lay hold at one another's end, and form the appearance of a vegetation."

3. Copper is amalgamated with mercury with great difficulty, and only by mixing blue vitriol with mercury and water in an iron retort over the fire. The acid then attacks the vessel, and the copper is precipitated in a metallic state, which, by stirring it with an hot iron spatula, unites to the mercury, but does not crystallize.

4. Two ounces of melted lead poured on a pound of mercury produce a half-fluid amalgam, which being decanted gives some crystals like those of silver. One ounce of these crystals retains an ounce and an half of mercury.

5. The amalgam of tin crystallizes into thin shining lamellae, with polygonous cavities between one another. Two ounces of tin retain six of mercury in this crystallization.

6. Mercury amalgamates with bismuth by means of heat, and produces crystals of an octohedral form, and lamellated triangles and hexagons. They are black on the upper surface, and shining underneath. In this crystallization the bismuth retains double its weight of mercury.

7. Zinc, in fusion, poured upon mercury, produces a crackling noise resembling that produced by a hot body thrown into boiling water. It crystallizes very well into lamellated hexagonal figures, leaving cavities among themselves. One ounce of zinc retains two and an half of mercury in this crystallization.

8. Quicksilver does not amalgamate with arsenic, except by heat, and then only in very small quantity. This metal answers very important purposes both in medicine and the arts. Though it has no perceptible taste, it produces very remarkable effects on the stomach and intestines of animals, as well as on the surface of the skin. Insects and worms are extremely sensible of this effect, and the metal, almost in any state, is exceedingly pernicious to them. Physicians, therefore, employ it as an excellent vermifuge (see Medicine, p. 341), and it is likewise one of the most powerful remedies in the materia medica for many obstinate disorders besides those of the venereal kind, in which its efficacy has long been celebrated. "Even the most virulent product of mercury (says Mr Magellan), known by the name of sublimate corrosive, which is the most violent poison, is often taken internally in very minute doses, under the direction of skilful physicians, and produces the most happy effects in a great variety of cases even of the most desperate kind. This is a fact which I have experienced myself, in a dreadful scrofulous complaint which I suffered for above four years, with reflexes and violent pains in the eyes and head. None of the most able physicians in London and Paris I consulted afforded me any effectual relief, till I had the good fortune to consult Mr Sacre surgeon-oculist at Antwerp. His prescription consisted of three grains of sublimate dissolved in a pint of common proof spirit. The dose consisted in taking every morning two spoonfuls of it in a pint of new milk. In less than two months I began to feel relief; and in three months time was completely cured. The first methodical practice of this remedy was communicated to the celebrated Van Swieten, first physician to the Emperor's court, by the late Dr A. R. Sanches, then chief physician to the court of Petersburg, as appears by the last volume of the Commentaries of the same Van Swieten, published in 1772. This volume was published after the author's death; but he had enjoyed during his life the glory of being the author of this wonderful remedy, which continues to bear his name among the ignorant and inaccurate physicians of our times."

But whatever uses this salt may be put to when taken in small quantities, it is certainly not less violent than arsenic itself, if taken in a large dose; and the danger is the greater, on account of the difficult solution of the salt, which requires for this purpose 19 times its weight of water. Alkaline salts, however, prove a very effectual antidote, and will instantly relieve the symptoms; but, on account of the insolubility of the poisonous salt, the disorders occasioned by it soon return, and require a repetition of the same remedy. In cases where alkaline salts are not immediately at hand, soap dissolved in water will answer the same purpose; or if this also should not be instantly procurable, chalk, lime, spirit of hartshorn, or magnesia alba, might be used with good effect.

Quicksilver is employed in Chili and Peru to extract gold and silver, when native, from the earthy matters with which they are mixed. The principle on which this method is founded is the strong mutual attraction betwixt mercury and the precious metals. By reason of this the smallest particles either of gold or silver form an amalgam with the mercury, part of which is strained off, and the remainder either separated by distillation... stillation in iron retorts, or by a kind of distillation per defecation; putting it in a kind of metallic sieve over a vessel of water, to receive the mercury, which is driven down by a fire lighted in a vessel above the amalgam.

The amalgam with gold serves also to gild copper or silver, so that they appear as if made of solid gold.—For this purpose the pieces are to be well cleaned, and then dipped in a weak aquafortis; then in a nitrous solution of quicksilver, which covers them with a kind of silvering. After this the amalgam of gold is very equally spread over them; which being done, the piece is exposed to a heat sufficient to volatilize the quicksilver, and the gold is then left strongly adhering to the metal. The only use to which the amalgam of mercury with lead has hitherto been applied, is the luting glass vessels in which specimens of natural history are to be preserved in spirit of wine. For this it is more proper than any other substance, having an excellent effect in preventing evaporation. The amalgam of tin is commonly employed in making looking-glasses or mirrors. The thin sheet of tin is laid down on a large flat table of stone; a proper quantity of mercury, in which some tin has already been dissolved to prevent it from destroying the tin sheet, is rubbed over with a bunch of cloth like a flat bung, and the glass carefully slid up on it from one end to the other, in such a manner that the dirty crust of the quicksilver is driven off before its edge; and the glass is then loaded with weights all over: by inclining gradually the stone table, the superfluous mercury is discharged; and in a few hours both cohere together. This amalgam is used for exciting the electricity of glass globes in the common electrical machines, but is said to be inferior in strength to that made with zinc.

Quicksilver heated by itself, with access of air, is by degrees converted into a red powder, improperly called Mercurus precipitatus per se. It consists of the calx of the metal united with the basis of dephlogisticated or pure air, which may be expelled from it again by a strong heat; and this was the first method by which Dr Priestley obtained this kind of air.

Mercury is not altered by the contact of air: It is only observed, that it becomes tarnished by the particles of dust which the air deposits; and from that circumstance mercury has been called the loadstone of dust.—Though all bodies have this property, it seems more remarkable in mercury than any other, on account of its great splendour; but it is not in the least changed by this circumstance, nothing more being necessary to restore it to its original brilliancy than filtration through a piece of shamoys leather.

The volatility of mercury prevents it from uniting with earths in the way of fusion; though M. Fourcroy is of opinion that its red calx, or precipitate per se, might perhaps fix in glasses, and colour them, as is observed in the calx of arsenic.