in medicine and anatomy, anything belonging to the liver.

HEPATIC Air, a permanently elastic fluid, of a very disagreeable odour somewhat like that of rotten eggs, obtained in plenty from combinations of sulphur with earths, alkalies, metals, &c. and sometimes from combinations of alkalies with substances which do not appear to contain any sulphur.

The nature of this fluid has been particularly examined by Mr Kirwan, of whose experiments we have an account in the 76th volume of the Philosophical Transactions, and of which the results are as follow.

1. By weighing it in a glass bottle exhausted in the most perfect manner by an air-pump, its specific gravity is found to be to that of common air as 10,000 to 9038.

2. Though inflammable, it never detonates with common air; nor can it be fired in a narrow-mouthed vessel, unless mixed with a considerable proportion of this air. Mr Scheele found that it would take fire when mixed with two thirds of common air; but M. Sennebier informs us that it cannot be fired by the electric spark even when mixed with any quantity of respirable air. Mr Kirwan found one part of the hepatic air, and one and a half of common air, to burn blue without flashing or detonating; and that, during the combustion, sulphur is constantly deposited, and a smell of vitriolic acid perceived. Mixed with an equal part of nitrous air, it burns with a bluish, green, and yellow lambent flame: it deposits sulphur also; and in proportion as the latter is deposited, a candle dipped in the air burns more weakly, and is at last extinguished. Two parts of nitrous and one of hepatic air burn partially. tially with a green flame; the residuum extinguishing a candle, which reddens on coming into contact with the atmosphere. One part of common air being admitted to equal parts of nitrous and hepatic air, sulphur was instantly precipitated, and the three measures reduced to 2.4; which burned on the surface with a greenish flame, but extinguished the candle when sunk deeper. Four parts of hepatic, with one of common air, burned rapidly with a blue flame; and a mixture of equal parts of dephlogisticated and hepatic airs which had stood eight days, went off with a report like a pistol, and to instantaneously that the colour of the flame could scarcely be discerned.

3. Hepatic air turns the tincture of litmus red, which Bergman supposes it would not do if it were washed; but Mr Kirwan found no alteration after passing two measures through water, or even after boiling the air out of water impregnated with it. Nay, the same hepatic air which had once reddened litmus, continued to do so after being put to a fresh quantity of the tincture.

4. There is a considerable difference in the miscibility of hepatic air with water according to the materials from which the former is made. By slight agitation, water in the temperature of 66° imbibes two thirds of its bulk of air extracted from alkaline or calcareous hepar by means of marine acid. An equal quantity of water dissolves three-fourths of its bulk of hepatic air extracted by the same acid from martial hepar; eight-tenths of that extracted by means of the concentrated vitriolic acid, or the dilute nitrous or saccharine acids in the temperature of 60°; seven-tenths of that extracted by sedative acid; nine-tenths of that made with the acetous acid, and of that afforded by oil of olives; and lastly, its own bulk of that produced from a mixture of sugar and sulphur. In general, however, that produced by the greatest degree of heat seems to be the most easily miscible; though in some instances, particularly that of acetous hepatic air, this does not take place.

5. The union between hepatic air and water is not permanent. Even when the water has been boiled in order to expel the air it naturally contains previous to its union with the hepatic air, the fluid grows very soon turbid, and deposits the hepatic air in the form of sulphur, though the bottle be ever so well corked, or stand inverted in water or mercury. The absorption of the air by water, however, does not seem to occasion any decomposition in the former, as the quantity left will be absorbed like the former by adding more water. It cannot be expelled from water till it comes near the boiling point.

6. No kind of hepatic air, excepting that produced from charcoal, precipitates lime from lime-water; and even this does it only in a very slight degree, unless a large quantity of air passes through a small one of water.

7. The most sensible test of the presence of hepatic air is the solution of silver in the nitrous acid. This, according as the nitrous acid is more or less saturated with silver, becomes black, brown, or reddish brown, by the contact with hepatic air, however mixed with common air or any other permanently elastic fluid. When the acid is not saturated, or is in large proportion, the brown or black precipitate, which is nothing but sulphurated silver, is redissolved.

8. All hepatic air suffers some diminution by standing over mercury, and blackens the surface of the metal; particularly that made from charcoal.

9. Mixtures of hepatic air with common, dephlogisticated, and phlogisticated airs, continued for a long time either totally undiminished or very little so, as did those also with inflammable marine acid air and fixed air; only blackening the surface of the mercury.

10. Two measures of hepatic air being introduced to two of vitriolic air, a whitish yellow deposition immediately covered the top and sides of the jar, and both airs were without any agitation reduced to little more than one measure. As the glass, however, was obscured by a whitish scurf over its whole inside, it was found necessary to repeat the experiment. One cubic inch of hepatic air was then added to five of vitriolic air; and, in less than a minute, without any agitation, the sides of the glass were covered with a whitish scum apparently moist, and a diminution of more than one ounce measure took place. In four hours after, a second measure of hepatic air was introduced; which was followed by a second deposition of whitish matter and diminution of the air. Next day three other measures were added at the interval of four hours between each; when, finding still a farther diminution, another measure was added next day. The whole quantity of 11 ounce measures was thus reduced at last to three, which seemed to be little else than phlogisticated air. The water in which the sulphur precipitated from the hepatic air was washed, and appeared to contain some vitriolic acid and fixed air.

11. A mixture of two measures of nitrous, and as much hepatic air, was little altered at first even by agitation; but, on standing 36 hours, both were reduced by something more than one third of the whole. The mercury was not blackened, but particles of yellow sulphur were deposited both upon the sides of the glass and the surface of the metal. The air which remained had still an hepatic smell, and was somewhat more diminished by water: a candle burned naturally in the unabsorbed part. The water had all the properties of that which had absorbed hepatic air. On adding nine cubic inches of nitrous air to eight of hepatic, a yellowish cloud instantly appeared, a slight white scum was deposited on the sides of the jar; and the whole seemed to be diminished about two cubic inches, the temperature of the room being then 72°. In 48 hours the whole was reduced to six cubic inches, and the top and sides of the jar covered with a cake of white sulphur; the heat of the room being constantly between 60 and 70°. The residuum was examined in 24 hours after, and had a pretty strong smell of alkaline air. A candle burned in it naturally; and it did not affect tincture of litmus, lime-water, or acetous barytes. It was not affected by any kind of air except the dephlogisticated kind, and this produced only a slight redness and diminution; it produced also a slight white precipitate in solution of silver. Hence it appeared that this was dephlogisticated nitrous air, or, as our author thinks, it ought rather to be called deacidified nitrous air.

12. Mr Kirwan supposing that an uncombined acid in the nitrous air was the cause of precipitation, he deprived some nitrous air of this acid as perfectly as possible before mixing it with hepatic air; which was done... done by admitting alkaline air to it, and then washing out the ammoniacal compound in distilled water. By being deprived of its acid it lost about one-fifth of its bulk; and it was diminished by common air in the same manner that nitrous air usually is. Seven cubic inches of hepatic air were then admitted all at once to eight of the purified nitrous air. No cloud or other mark of any precipitation appeared; but in five hours the whole was reduced to five cubic inches, the temperature of the room being 76°; but the diminution went no further in 18 hours after. A much whiter sulphur was deposited than in the former experiment; and both in this and the former, that part which was intercepted by the rising of the mercury betwixt the metal and the side of the jar was of a yellow and red shining colour, and not black, as that deposited in mercury usually is. The residuum flamed with such violence as to extinguish a candle dipped into it, the flame being exceedingly white and vivid; though it did not detonate in the least, but rather appeared like deplogisticated air. The jar out of which it had been transferred had a strong alkaline smell. It was not in the least diminished by nitrous air, even when heated to 150 degrees.

Water poured into the jar in which the sulphur was deposited produced a bluish white cloud in solution of silver, though insipid to the taste; whence it appears, that whatever this air may be, it had been decarbed by hepatic air still more perfectly than that in which a candle burns naturally, but was by no means deplogisticated.

13. Perfectly pure alkaline and hepatic airs mixed together would probably destroy each other; but Mr Kirwan never had it in his power to do this entirely. Six measures of hepatic air from liver of sulphur, and six of alkaline air, immediately throw up a white cloud, leaving a whitish scum on the side of the jar, and are reduced to about one ounce measure. On adding water this is reduced to about one half; and a candle burns naturally in it. This residuum, however, was afterwards found to be only the common air of the vessels.

14. One measure of oil of vitriol, of the specific gravity of 1.863, absorbed two measures of hepatic air all to one-tenth; the acid being whitened by a copious deposition of sulphur.

15. A measure of red nitrous acid, of the specific gravity of 1.430, was introduced to an equal measure of hepatic air; red vapours instantly arose; and only one-tenth or one-twelfth of a measure remained in an aerial form; but as the acid acted on the mercury, it was necessary to use water, by which the whole was absorbed. No sulphur was precipitated on this occasion. The experiment was repeated in another manner, but with little success; so that Mr Kirwan, finding it so difficult to use the concentrated nitrous acid, determined to try its effects upon hepatic air by diluting the acid to such a degree that it could not act upon mercury without the assistance of heat. In this case the acid was whitened, eight-tenths of the air absorbed, and the residuum detonated. A still greater quantity was absorbed when the experiment was made with hepatic air made from liver of sulphur; but the residuum, instead of detonating, burned with a blue and greenish flame, depositing sulphur upon the sides of the jar. This dilute acid absorbed about three times its bulk of hepatic air; but on expelling the same from it again by heat, the fifth part only was obtained, and in this a cauldron burned naturally.

16. Two measures of alkaline hepatic air were absorbed by one of strong marine acid to one-fifth of a measure, after a slight agitation. On adding a third measure of hepatic air, the whole was absorbed to half a measure. The sulphur precipitated in this experiment was attracted by the mercury, and blackened it; which did not happen in the former cases, by reason of the stronger attraction of the acid for the sulphur. The residuum burned as pure hepatic air.

17. Distilled vinegar absorbs nearly its own bulk of hepatic air, and becomes slightly whitened; but by agitation it may be made to take up about twice its bulk, and then becomes very turbid.

18. One measure of caustic vegetable alkali, the specific gravity of which was 1.043, absorbed nearly four measures of alkaline hepatic air, which rendered it brown at first, but after some time it grew clear and deposited sulphur, blackening the surface of the mercury.

19. One measure of caustic volatile alkali, of the specific gravity of 0.9387, absorbed 18 of hepatic air. A greater quantity of alkali would absorb more hepatic air, fix measures of the alkaline air uniting to seven of the hepatic; and thus the strength of alkaline liquors, and their real contents, may, according to our author, be determined better than by any other method. The smoking liquor of Boyle (a strong volatile tincture of sulphur) may be easily prepared by putting volatile alkali in the middle vessel of Dr Nooth's apparatus, and decomposing liver of sulphur, or artificial pyrites in the lowermost one by means of marine acid.

20. Olive oil absorbs nearly its own bulk of hepatic air, and gets a greenish tinge from it.

21. Oil of turpentine absorbs more than its own bulk of this air, but then becomes turbid. A white cloud appears when water is put to the mixture.

22. Spirit of wine, of the specific gravity of 0.835, absorbed nearly three times its bulk of hepatic air, and became brown. Thus sulphur may be combined with spirit of wine more easily than by the method used by Count Louragais, the only one hitherto known. Water partly precipitates the sulphur.

23. New milk scarcely absorbs one-tenth of its bulk of this air, and is not in the least coagulated.

24. With an equal bulk of vitriolic ether the bulk of the air is at first increased; but afterwards one-half is absorbed, and a slight precipitation appears. The smell is compounded of that of ether and hepatic air; but on adding water it becomes very offensive, resembling that of putrefying animal substances.

25. On adding a measure and an half of nitrous solution of silver to one of hepatic air, the latter was absorbed immediately, and without any agitation, the solution at the same time becoming black. The remaining air admitted a candle to burn naturally in it. Hepatic air was likewise absorbed, but with more difficulty, and in smaller quantity, by the vitriols of iron and silver; the latter was blackened; the former became white at first, but darker by agitation; the residuum burned blue, as hepatic air usually does. 26. Sulphurated spirit of wine precipitates lime-water, which highly rectified spirit of wine will also do by itself. It also precipitates and gives a brown colour to acetous baro-felenite, which is likewise done by spirit of wine: the solution of silver is turned black or brown by it. Sulphur is precipitated from it by concentrated vitriolic acid, which cannot be done either by the nitrous or muriatic acids.

27. Water saturated with hepatic air turns the tincture of litmus red; does not affect lime-water; forms a cloud in the solution of acetous baro-felenite, though not in that of the marine: it does not alter the solutions of other earths. It produces a white precipitate in the solution of vitriol of iron, or solution of that metal in spirit of salt; in nitrous solution of copper it throws down a brown precipitate, and the colour of the liquid is changed from blue to green; the precipitate being redissolved by agitation. In solution of vitriol of copper it forms a black precipitate. It throws down a yellowish white precipitate in solution of tin in aqua-regia; a black one from solution of gold; a red and yellow one from that of antimony; and one of red mixed with white from solution of platinum. Black precipitates are formed with nitrous solutions of lead and silver; but if these are not perfectly saturated with metal, the solutions will be brown, or reddish brown, and may be redissolved by agitation. Nitrous solution of mercury is precipitated of a yellowish brown; corrosive sublimate of a yellow mixed with black, but which becomes white by agitation. Nitrous solution of bismuth becomes reddish brown, and even assumes a metallic appearance. Solution of cobalt becomes dark; that of arsenic in nitrous acid becomes yellow, mixed with red and white; forming realgar and orpiment. On dropping into hepatic water oil of vitriol of the specific gravity of 1.863, the mixture becomes slightly turbid; but on dropping into it the volatile vitriolic acid, a bluish white and much denser cloud is formed. A copious white precipitation is occasioned by the strong nitrous acid, whether philosophicated or not; but dilute nitrous acid produces no change. Green nitrous acid, the specific gravity 1.328, instantly produces sulphur. A flight cloud is produced by strong marine acid; but neither distilled vinegar nor acid of sugar has any such effect. According to Mr Bergman, hepatised water, in a well closed vessel, will dissolve iron in a few days; but the experiment did not succeed with Mr Kirwan, neither could he dissolve any other metal in this water, though the sulphur united with many of them into an insoluble mass; whence our author concludes, that metallic substances cannot be found in hepatised waters.

28. Colourless alkaline liquors acquire a brownish tinge from hepatic air; the residuum they leave being of the same nature with what they absorb. A caustic fixed alkaline liquor, saturated with this air, precipitates barites from the acetous acid of a yellowish white colour; decomposing likewise other earthy solutions, and the precipitate varying according to their purity; a test which our author supposes may be improved to such a degree as to supply the place of the Prussian alkali. It precipitates also solution of vitriol of iron as well as marine salt of iron, of a black colour; but the latter generally whitens by agitation. Solutions of silver and lead are also precipitated black with some mixture of white: that of gold is also blackened; and solution of platina becomes brown. Solutions of copper let fall a reddish black or brown precipitate. Sublimate yields a precipitate partly white and black, and partly orange and greenish. A nitrous solution of arsenic forms a yellow and orange precipitate; and that of regulus of antimony in aqua-regia, an orange precipitate mixed with black. Nitrous solution of zinc yields a dirty white precipitate; that of bismuth a brown mixed with white; and that of cobalt a brown and black precipitate. Prussian alkali yields a purple precipitate, which is easily redissolved. Tincture of radishes, our author's test for alkalies, was turned green.

29. On adding a few grains of iron, copper, lead, tin, zinc, bismuth, regulus of antimony, and arsenic, to a solution of liver of sulphur, all the metals were found to attract sulphur from the fixed alkali, excepting zinc and tin. Iron, arsenic, regulus of antimony, and lead, were most altered; copper next, and bismuth the least. No part of the metals appeared to be dissolved.

30. Water saturated with the condensed residuum of alkaline and hepatic air, i.e., with the purest volatile liver of sulphur, does not precipitate marine felenite, though it forms a flight brown and white cloud in that of marine baro-felenite. It throws down a black precipitate in solution of vitriol of iron, and a black and white one in that of marine salt of iron; but by agitation this became entirely white. Vitriol of copper, and nitrous salt of the same metal, are both precipitated of a brown and red colour. Tin dissolved in aqua-regia yields a yellowish precipitate; gold, a dilute yellow and reddish brown; platina, a flesh-coloured precipitate; and regulus of antimony, a yellowish red. Silver is precipitated black, as well as lead, from the nitrous and acetous acids. Corrosive sublimate became red for a moment; but in a little time its precipitate appeared partly black and partly white. A similar precipitate is afforded also by the nitrous solution of bismuth; but partly mixed with a reddish-brown colour, and has something likewise of a metallic appearance; the precipitate of cobalt is black, or deep brown. Solutions of arsenic yield precipitates of a yellow colour, and more or less red; those of zinc of a dirty white.—All these colours, however, vary, as the liquors are more or less saturated previous to and after their mixture, and the time they have stood together.

From these experiments Mr Kirwan concludes, that hepatic air consists merely of sulphur rarefied by elementary fire, or the matter of heat. Some have supposed that it consists of liver of sulphur itself volatilised; but this our author denies, for the following reasons: 1. It is evidently, tho' weakly, acid; reddening litmus, and precipitating acetous baro-felenite, though none of the other solutions of earths. 2. It may be extracted from materials which either contain no alkali at all, or next to none; as iron, sugar, oil, charcoal, &c. 3. It is not decomposed by marine or fixed air; by which nevertheless liver of sulphur may be decomposed.

Our author informs us, that he was formerly of opinion that sulphur was held in solution in hepatic air, either by means of vitriolic or marine air: but neither of these is essential to the constitution of hepatic air as such, since it is producible from materials that contain neither of these acids; and from whatever substance: it is obtained, it always affords the same character, viz. that of the vitriolic acid exceedingly weakened, such an acid as we may suppose sulphur itself to be. This substance indeed, even in its concrete state, manifests the properties of an acid, by uniting with alkalies, calcareous and ponderous earths, as well as with most metals, which a very weak acid might be supposed to do.

As phosphorus bears a considerable resemblance in its constitution to sulphur, Mr Kirwan determined to make some experiments upon it in similar circumstances. He therefore gently heated 10 or 12 grains of phosphorus mixed with about half an ounce of caustic fixed alkaline solution in a very small vial furnished with a bent tube, and received the air over mercury. Two small explosions took place on the first application of heat, attended with a yellow flame and white smoke, which penetrated through the mercury into the receiver. This was followed by an equable production of air; but at last the phosphorus began to swell and froth up, burst with a loud explosion, and a violent flame immediately issued from it. Only about eight cubic inches of air were obtained. These were but very slightly diminished by agitation in water; after which a cloudiness took place, but the air soon recovered its transparency. Water impregnated with it slightly reddened tincture of litmus, but did not affect Prussian alkali. It had no effect upon the nitrous solutions of copper, lead, zinc, or cobalt; nor on those of iron or tin in marine acid and aqua-regia; nor on the vitriolic solutions of iron, copper, tin, lead, zinc, regulus of antimony, arsenic, or manganese; nor on the marine solutions of iron, copper, lead, zinc, cobalt, arsenic, or manganese. The nitrous solution of silver was precipitated of a black colour, and the vitriolic of a brown; nitrous solution of mercury, made without heat, precipitated a brown or black powder; but vitriol of mercury first became reddish, and afterwards white; corrosive sublimate a yellow mixed with red and white. Gold dissolved in aqua-regia is precipitated of a purplish black, and in the vitriolic acid of a brownish red and black; but regulus of antimony dissolved in aqua-regia is precipitated of a white colour. Nitrous solution of bismuth let fall a sediment at first white, and afterwards brown; vitriol of bismuth and marine salt of bismuth were also precipitated brown, the latter being redissolved by agitation. Nitrous solution of arsenic also became brown, but the precipitate was redissolved by agitation. On impregnating water with this air, without allowing the air to burn over it, the liquid scarcely made any alteration in tincture of litmus, nor did it precipitate lime-water; but caused a black precipitate in solution of silver; a white one in solution of regulus of antimony in aqua-regia, and a whitish yellow one in that of corrosive sublimate.

On letting up a measure of water to this air, and through that some bubbles of common air, every bubble flamed, and produced a white smoke until about half the quantity of common air was introduced that had been used of phosphoric; but without any apparent increase of the original bulk. The flame produced a small commotion each time, and smoke descended after the inflammation into the water; the smoke still continuing to be produced on the introduction of common air, after the flame had ceased. Bubbles of phosphoric air, escaping through mercury in

to the atmosphere, flame, crackle, and smell, exactly like the electric spark. This property of phosphoric hepatic air was known to M. Gingembre in the year 1783.

On letting up half a measure of nitrous to one of phosphoric air, a white smoke appeared, with a very slight diminution; the transparency being soon restored, and a slight scum deposited on the sides of the jar. No smoke or diminution was produced by adding another half measure of nitrous air; but on adding water, and agitating the air in it, much more was absorbed. On turning up the jar, the nitrous air first escaped in form of a red vapour, and this was followed by a whitish smoke. The water had a phosphoric smell, and precipitated the solution of silver brown.

An equal measure of alkaline air scarcely diminished phosphoric air; and on adding water, little more seemed to be taken up than the alkaline air, though a smoke appeared on turning up the jar, but without any flame. Water thus impregnated smelled exactly like onions, and turned the tincture of radishes green. Solution of silver was precipitated of a black colour; that of copper in the nitrous acid, of a brown; the precipitate being redissolved by agitation, and the liquor then assuming a green colour. Corrosive sublimate let fall a yellow precipitate mixed with black. Iron was precipitated white both from the vitriolic and marine acids; but a pale yellow solution of it in the nitrous acid was not affected, and a red solution in the same acid was only clotted. Regulus of antimony was precipitated of a white colour from aqua-regia, cobalt of a slight reddish from the nitrous acid, and bismuth of a brown colour from the same. Neither the nitrous solutions of lead or zinc were affected; nor those of tin in the marine acid or in aqua-regia. Fixed air, mixed with an equal proportion of phosphoric air, produced a white smoke, some diminution, and a yellow precipitate. On agitating the mixture in water the fixed air was taken up all to one-tenth; the residue smoked, but did not take fire.

Some precipitate per se being introduced to a small portion of phosphoric air, the former soon grew black, and a white smoke appeared. In two days the precipitate became solid, acquiring a pale white colour, shining like steel. The air lost its inflammability; though Mr Kirwan supposes that this might be owing to some other cause: for two days after this air was made, a yellow scum was observed on the sides of the jar in which a quantity of it had rested all night over water; and the spontaneous inflammability was lost next morning. The temperature of the air was then 53°; and when it inflamed before 68°.

From these experiments our author concludes, that phosphoric air is nothing else but phosphorus itself in an aerial state; differing from sulphurous or hepatic air in this, that it requires much less latent heat to throw it into an aerial state, and therefore may be disengaged from fixed alkalies without any acid.

Hepatic air may be obtained in a great number of different ways, and from a variety of substances. The most common method in which it has been procured, is by decomposing the hepatic sulphuris or combination of sulphur and fixed alkaline salt by means of an acid. Mr Kirwan has examined the circumstances attending the formation of liver of sulphur; making his first experiment periment by melting together equal parts of the mineral alkali and flowers of sulphur in a covered crucible. On slightly heating the mixture, it emitted a bluish smoke, which gradually became whiter as the heat was augmented; and at last, when the bottom of the crucible became slightly red, the smoke was perfectly white and inflammable. To investigate the nature of this smoke, a pure fixed alkali was made by deflagrating equal parts of cream of tartar and nitre in a red-hot crucible in the usual way. This alkali, in a very dry state, was mixed with a small quantity of flowers of sulphur, and the mixture distilled in a small coated retort; the air being received over quicksilver.

On the first application of heat, one cubic inch and an half of slightly phlogiticated air was obtained, but without any fixed air. This was the common air contained in the vessels, but altered by being in contact with the alkali and sulphur. On augmenting the heat, about 18 inches of air were obtained, of a reddish colour, seemingly a mixture of nitrous and common air; acting slightly on mercury. After this, 20 cubic inches of the same kind mixed with some fixed air were obtained. These were succeeded by 64 inches of fixed air almost perfectly pure. The bottom of the retort was now red-hot; some sulphur was sublimed in the neck; and when all was cold, an hepar sulphuris was found in the bulb.

From this experiment Mr Kirwan concludes, that the blue smoke above mentioned consists chiefly of fixed air and the white of sulphur; but that neither hepatic nor vitriolic air are formed unless the retort be large enough to admit as much air as is necessary for burning part of the sulphur. He concludes also, that hepar sulphuris will yield no hepatic air unless with the help of an acid; "and I believe this (says he) to be true, when the experiment is made in the dry way, and nearly so in the moist way: for having added 200 grains of sulphur to a concentrated solution of strong caustic vegetable alkali by a strong and long-continued heat, I obtained only one cubic inch of hepatic air; yet it is well known, that a strong solution of liver of sulphur constantly emits an hepatic smell, even in the temperature of the atmosphere; and the substance so emitted contains as much hepatic air as discourses silver and lead, and even their solutions; which shows that an incomparably small quantity of this air is sufficient to produce the effect. To discover whether this extraction of hepatic air might be caused by the deposition of fixed air from the atmosphere, I threw some pulverized calcareous hepar into aerated water, and by the application of heat endeavoured to obtain hepatic air, but in vain: and indeed the very circumstance that the hepatic smell and its effects are always strongest the first instant that a bottle of the hepatic solution is opened, seems to indicate that fixed air is no way concerned in its production. The best liver of sulphur is made of equal parts of salt of tartar and sulphur; but as about one-fifth of the salt of tartar consists of air which escapes during the operation, it seems that the proportion of sulphur predominates in the resulting compound; yet, as some of the sulphur also sublimes and burns, it is not easy to fix the exact proportion. One hundred grains of the best, that is to say the reddest liver of sulphur, afford with dilute marine acid about 40 inches of hepatic air in the temperature of 60°; a quantity equivalent to about 13 grains of sulphur, as will be seen in the sequel."

Hepatic air is best produced by marine acid: the concentrated nitrous acid produces nitrous air; but if diluted with 20 times its bulk of water, it produces the hepatic kind by the affluence of heat. Concentrated vitriolic acid poured upon liver of sulphur affords but little hepatic air without the affluence of heat; though it constantly decomposes the hepar; "and (adds our author) it is partly for this reason that the proportion of air is so small; for it is during the gradual decomposition of sulphureous compounds that hepatic air is produced." Hepatic air, but not in a pure state, is extracted by distilled vinegar; its smell being mixed with that of the vegetable acid. Some quantity of this air is produced by the saccharine acid in the temperature of 59°, and by sedative salt in that of boiling water or nearly so; but neither the arsenical nor aerial acids produce any.

Having prepared some hepar sulphuris with an over proportion of sulphur, an hepatic air was procured by means of concentrated vitriolic acid; but so loaded with sulphur, that it deposited some in the tube through which it was transmitted, and on the upper part of the glass receiver. On transferring it to another receiver, though then perfectly clear and transparent, in quantity about five cubic inches, yet next morning it was reduced to one inch, the inside of the glass being covered with a thick coat of sulphur; the small quantity of elastic fluid which remained being changed from hepatic to vitriolic air. "Hence (says Mr Kirwan) it appears, first, that a species of elastic fluid may exist in a state intermediate between the aerial and vaporous, which is not permanently elastic like air, nor immediately condensed by cold like vapour; but which, by the gradual loss of its specific heat, may be reduced to a concrete form. 2. That so large a quantity of sulphur may be combined with vitriolic air, as to enable it to exhibit the properties of hepatic air for some time at least. A mixture of three parts of pulverized quicklime and one of sulphur, heated to whiteness in a covered crucible for one hour, became of a flaky hardness; and, being treated with marine acid, afforded hepatic air. On heating a piece of this stone in pure water, it becomes bluish; and hence the origin of blue marbles generally found near hot sulphurated waters. A calcareous hepar may also be formed in the moist way."

Magnesia deprived of its fixed air, and heated in the same manner with sulphur, afforded no hepatic air. It was procured, however, from a mixture of three parts of iron-filings and one of sulphur melted together, and treated with marine acid. This sulphurated iron dissolved in marine acid affords almost entirely hepatic air, and very little of the inflammable kind. Equal parts of iron-filings and sulphur mixed together, and made into a paste with water, after heating and becoming black, afforded hepatic air when an acid was poured on it; but this was mixed with inflammable air, probably proceeding from uncombined iron. After a few days this mixture lost its power of producing hepatic air. Mr Bergman has also remarked, that combinations of sulphur with some other metals yield hepatic air.

Hepatic air was obtained by pouring some olive-oil upon a few grains of sulphur, and heating the mixture in a vial with a bent tube. It was likewise obtained in great plenty from equal parts of sulphur and powdered charcoal, out of which the air had previously been expelled as much as possible: "yet (says our author) it is hardly possible to free charcoal wholly from foreign air, for it soon reattracts it when exposed to the atmosphere."

Six grains of pyrophorus mixed with alum and sugar effervesced with marine acid, and afforded two cubic inches and an half of hepatic air. This pyrophorus had been made six years before, and was kept in a tube hermetically sealed, and for several summers exposed to the light of the sun. It was so combustible, that some grains of it took fire while it was introduced into the vial out of which the hepatic air had been expelled.

A mixture of two parts of white sugar (previously melted in order to free it of water) with one part of sulphur, when heated to about 600 or 700 degrees, gave out hepatic air very rapidly. This air had a smell very much resembling that of onions, but contained neither fixed air nor any other acid. Sugar and sulphur melted together gave out no hepatic air when treated with acids. Water, spirit of wine, and marine acid, decompose this mixture, dissolving the sugar, and leaving the sulphur.

Twelve grains of sulphur heated in a retort, filled with metallic inflammable air, afforded no hepatic air; though the retort smelled of it when cold, and for some time after.

Eighteen grains of liver of sulphur exposed for four days to six cubic inches of fixed air, the thermometer at 70°, was somewhat whitened on the surface; the air not having an hepatic smell, but rather that of bread. It seemed to have taken up some sulphur, which was separated by lime-water. It was not in the least diminished; and therefore seems to have received an addition of hepatic air, or rather of sulphur.

On exposing a quantity of sulphureo-martial paste to fixed air for five days, the latter was not at all diminished, but received a slight addition of inflammable air. The paste itself, taken out of this air and exposed to the atmosphere, heated very strongly.

Three grains of sulphur exposed to twelve inches of marine air was not diminished in four days. On adding a cubic inch of water to this air, it was all absorbed to one inch, which had an hepatic smell, as had also the water, the latter evidently containing sulphur.

Hepatic air is found naturally in coal-pits, and has been discovered by Mr Bergman to be the principle on which the sulphureous properties of many mineral waters depend. There is also great reason to think that it is the peculiar production of the putrefaction of many, if not all, animal substances. Rotten eggs and corrupted water are known to emit this species of air, and also to discolour metallic substances, in the same manner. M. Viellard has lately discovered several other indications of this air in putrefied blood. In the 80th volume of Philosophical Transactions, p. 391, Dr Crawford gives an account of some experiments, from which it appears, that a kind of hepatic air is contained in the virus of cancers. Having obtained a portion of this ichor from a cancerous breast, he divided it into three parts, which were put into separate vials after being properly diluted with water. To one of these he added some vegetable fixed alkali, to another a little concentrated vitriolic acid, and to the third some syrup of violets. No change was produced by the vegetable alkali; but on the addition of the acid, a deep brown colour was produced, and a brisk effervescence took place, at the same time that the peculiar odour of the cancerous matter was greatly augmented, and diffused itself to a considerable distance. A faint green colour was communicated to the third portion which had the syrup of violets.

As the cancerous matter on which these experiments were made had been previously kept some days, Dr Crawford suspected that it might thus have acquired its alkaline property; as Mr Geber has shown, that animal substances, when newly putrefied, do not contain any alkali. He repeated the experiment, therefore, on some matter recently procured from a cancerous penis. A manifest effervescence, though less than the foregoing, also took place in this case; the liquor acquired a brown colour, and the fetor increased. A portion of the same matter, diffused through distilled water, communicated a green colour as before; but in some cases the change was scarcely perceptible, though in all the experiments which were made the existence of an alkali one way or other was manifested.

The air extricated from the cancerous matter seemed by its smell to resemble rotten eggs more than any other species; but to investigate the matter fully, some portion of the virus was diffused through distilled water, the liquor filtered, and a small quantity of nitrous solution of silver dropped into it. An ash-coloured precipitate soon appeared diffused like a cloud through the liquid, and at the end of two hours the colour of the mixture was changed to a deep brown. The fetid smell was now rendered much fainter, and was entirely destroyed by an addition of concentrated nitrous acid, or by dephlogisticated spirit of salt; either of which substances would also have destroyed the smell of hepatic air.

On adding the vitriolic acid to common pus, no effervescence was produced, nor was the colour of the liquor changed, neither did any sensible precipitation take place for several hours. On repeating the experiment, however, with matter obtained from a venereal bubo, the liquid became slightly turbid on the addition of nitrated silver, and at the end of two hours it had acquired a brownish cast. The same effects took place with the matter which issued from a carious bone; but in both cases the precipitation was much less than with the cancerous matter.

To procure some quantity of the air in its separate state, a quantity of reddish cancerous matter was mixed with about thrice its weight of distilled water. On adding a little vitriolic acid to this mixture, an effervescence ensued, and the air was received in a vial over mercury. When one-half of the mercury was expelled from the vial, the latter was inverted over distilled water; and the portion of mercury that remained in it being suffered to descend, and the water to rise into its place, the vial was closely corked. The air and water were then briskly agitated together; and the vial being a second time inverted over distilled water, the cork was removed. It now appeared, by the height to which the water rose, that part of the air had been absorbed; and on dropping in a little nitrate... ted silver into it, a purplish cloud, inclining to red, was produced. In this experiment, the change of colour was at first scarcely perceptible, but became very distinct in a few minutes. The quantity of aerial fluid, however, which can thus be extricated by the addition of acid without heat is not very considerable; if heat be applied, a larger quantity of elastic fluid will be produced, having the smell of cancerous matter; but in that case it will be mixed with vitriolic acid air.

To obtain this air in as pure a state as possible, a portion of the cancerous virus, properly diluted with distilled water, was introduced into a small vial, a little vitriolic acid added, the vessel filled with distilled water, and a crooked tube also filled with water fitted to its neck. The extremity of the tube being then introduced into the neck of a bottle inverted in water, and the flame of a candle applied to the bottom of the vial, air began to rise in white bubbles, having a very fetid smell similar to that of cancerous matter; and the water impregnated with it occasioned a dark brown precipitate in a solution of nitric acid. On separating the crooked tube from the vial, a very offensive white vapour, resembling in smell the air produced in the foregoing experiment, arose from the mixture, and continued to ascend for near half an hour. A portion of the liquor filtered, and mixed with a little concentrated nitrous acid, had its smell entirely destroyed; a slight effervescence being produced, and a flaky substance separated from the liquor and floating through it.

On examining the alkaline matter which had been separated from the cancerous virus, it was found, as had indeed been concluded a priori, to be the volatile alkali. It seemed probable that this alkali was united to the fixed air with which the cancerous matter was impregnated, because the peculiar smell of the matter was greatly augmented by the addition of the vitriolic acid; and this was confirmed by the following experiments.

1. A portion of cancerous matter was diffused through distilled water, and distilled in a small retort with a graduated heat until the bottom of the vessel became red hot. The common air, which first came over, was greatly impregnated with the smell of the cancerous matter; however, its qualities were not greatly impaired by the tinct of nitrous air; two measures of it, with one of nitrous air, occupying the space of little less than two measures. When the water began to boil, a large quantity of aqueous vapour arose; which, as soon as it came into contact with the air, produced a white smoke. The smell was now perceived to be similar to that of boiled animal substances; but no permanently elastic fluid was mixed with the aqueous vapour. When the greater part of the water was evaporated, the jar containing the first portion of air was removed, and the neck of the retort introduced beneath an inverted vessel filled with mercury. A considerable quantity of air smelling like burnt bones was now extricated, which was mixed with a yellow empyreumatic oil. On agitating some of it with water, part of the air was imbibed. Nitric acid, dropped into the water thus impregnated, produced a reddish precipitate.

2. One measure of the air obtained in the foregoing experiment was mixed with an equal quantity of alkaline air. In three hours the whole occupied only the bulk of one measure and two-tenths, and an oily film was now left upon the inner surface of the tube; and in eight days the interior surface of the tube was covered with slender films of a yellowish colour spread irregularly upon it. The upper surface of the mercury within the tube was corroded; in some places having a reddish burnished appearance, in others it was changed into an ash-coloured powder interspersed with brown spots. On removing the tube from the mercury, the air that remained in it had a strong fetid smell, resembling that of burned bones.

3. To discover whether other animal substances yield an aerial fluid similar to that produced from the cancerous virus, a portion of the flesh of the neck of a chicken was distilled in a small coated glass-retort till it became red hot. A thin phlegm of a yellowish colour first came over; this was succeeded by a yellow empyreumatic oil; and at the same time a permanently elastic fluid, smelling like burned feathers, began to be discharged. A slip of paper tinged with limewater, and reddened by acetic acid, being held over this fluid, presently became blue. The remainder of the air was very fetid, and highly inflammable. By agitation in water one-half of it was absorbed; the remainder was inflammable, and burned first with a slight explosion, and afterwards with a blue lambent flame. On dropping a nitrous solution of silver into the water impregnated with this air, the mixture deposited a brown precipitate.

4. On treating putrid veal by distillation with a graduated heat, the products were found to be nearly similar to those already mentioned. The air obtained was highly inflammable, about one-half of it was absorbed by water; and the liquid thus impregnated let fall a brown precipitate on the addition of nitrous solution of silver. On adding some dephlogisticated marine acid to another portion of this liquor, a brisk effervescence took place, and a whitish gelatinous matter was separated; and this substance being evaporated to dryness, became black on the addition of the concentrated vitriolic acid. On agitation with water, part of the air was absorbed as in the former experiment, and the remainder burned with a lambent flame. This air, however, extricated from putrid veal, had less of an empyreumatic smell than that which was discharged from fresh animal substances, being rather like that of putrefying animal matters.

From these experiments our author concludes, that the air extracted from animal substances consists of two distinct fluids, the one soluble and the other insoluble in water. The insoluble part burns with a lambent flame, and has all the characters of heavy inflammable air; but the soluble part resembles that which is produced from cancerous matter by the vitriolic acid; having a fetid odour, decomposing nitric acid, combining with caustic volatile alkali, and possessing many of the properties of common hepatic air. In many particulars, however, the animal hepatic air differs from the common. The smell is considerably different, and in the decomposition of animal hepatic air no sulphur is separated, but a kind of flaky matter which is evidently an animal substance, as turning black by the vitriolic acid. The following experiment is a decisive proof proof that no sulphur is contained in animal hepatic air. "Equal parts of pure air, and of air extricated from fresh beef by distillation, were fired by the electric shock in a strong glass tube over mercury. A little distilled water was then introduced through the mercury into the tube, and was agitated with the air which it contained. A portion of this water being filtered, and a small quantity of muriated barytes being dropped into it, the mixture remained perfectly transparent. Hence it appears, that the air extricated by distillation from fresh beef does not contain sulphur, as that substance would have been changed by burning into the vitriolic acid, and the muriated barytes would have been decomposed. The same experiment was frequently repeated with air extricated by distillation from the putrid as well as from the fresh muscular fibres of animals; but in no instance could the least vestige of vitriolic acid be discovered.

5. To analyse in a more perfect manner these kinds of animal airs, and to determine their products when combined with pure air, about an ounce of the lean of fresh mutton was exposed to a red heat in a small coated glass retort. Very near one half of the air produced towards the end was absorbed by water, and two-thirds of that which came over about the middle. A separate portion of the air, disengaged towards the end of the distillation, being allowed to remain over mercury for seven hours, it was found gradually to diminish in bulk; and a fluid, having the colour and smell of a thin empyreumatic oil, was collected at the bottom of the jar. This appearance, however, is not constant: the air, when placed over mercury, sometimes diminishes, and at other times retains its original bulk. Only one-eighth part of this air was absorbed by water. "Hence (says the Doctor) it appears, that a portion of the air extricated from animal substances by heat, resembles a species of hepatic air which was first discovered by Mr Kirwan, and which exists in an intermediate state between the aerial and the vaporous; this fluid not being permanently elastic like air, nor immediately condensed by cold like vapour, but gradually assuming the nonelastic form, in consequence probably of the tendency of its several parts to unite with one another."

6. To determine the proportion of fixed air contained in that produced from the lean of animal substances, a quantity of air extracted from mutton was received over mercury in a large vial with a narrow neck. When the vial was little more than half filled, the remaining portion of the mercury was displaced by introducing water that had been previously boiled. The vial being then closely corked, the air and water were briskly agitated together; and the liquor, thus impregnated with the soluble part of the animal air, was put into a vial to the bottom of which heat was applied. Thus a part of the air was again disengaged, and received in a tube inverted over mercury; and the process continued till the liquor no longer rendered lime-water turbid. On agitating the air a second time with water, and comparing the bulk after agitation with that before it, it appeared that the quantity absorbed was about one-fourth part. From this experiment also it appeared, that animal hepatic air, when once absorbed by water, is not capable of being again disengaged by a boiling heat; for after the fixed air had all been expelled, the liquor was made to boil nearly for half an hour, but no permanently elastic fluid could be disengaged: that portion of the liquor which remained had a faint yellow colour, and smelled strongly of animal hepatic air, depositing also a brown precipitate upon the addition of nitrated silver. "It appears therefore (says the Doctor), that the soluble part of the air disengaged from animal substances by heat, consists of three distinct fluids; of alkaline air, fixed, and animal hepatic air. It seemed extremely probable, that these three aerial fluids, slowly combining together, formed the oily empyreumatic substance which was collected at the bottom of the jar, while the air was undergoing the diminution described above. In this conclusion I was confirmed by trials that were made with the empyreumatic oil that came over in the latter part of the distillation: for when it was examined by chemical tests soon after it was obtained, it was found to contain fixed air, volatile alkali, and animal hepatic air."

7. To determine the products resulting from the combustion of pure air with the animal hepatic air, one portion of the air extracted from the lean of mutton was agitated with water, the other was not. One measure of the former was introduced over mercury into a strong glass tube, and then mixed with one measure and an half of pure air. A small shock being made to pass through it, a violent explosion took place; and the space occupied by the air in the tube was reduced from an inch and two-tenths to nine-tenths of an inch. On agitating the residuum with water, five-tenths were absorbed; and the portion absorbed appeared to be fixed air by its precipitating lime-water. Five parts of nitrous air being mixed with an equal quantity of the insoluble residuum, a diminution of three parts took place; whence it appears that one-fifth of the insoluble residuum was pure air. Hence it appears that fixed air was produced by the inflammation of deploglificated and animal hepatic air.

8. One measure of that portion of animal air which had not been agitated with water was mixed with a measure and an half of pure air, and fired by the electric shock. Previous to the deflagration, the two airs occupied the space of 1.15 inches, but afterwards it was reduced to 1.1. On agitation with water, about one-third was absorbed; a portion of the insoluble residuum burned with a faint blue flame.

9. As it appeared from these experiments, that a measure and an half of deploglificated air was not sufficient to saturate one of the animal air that had not been agitated with water, the experiment was repeated in the following manner. Two parts of pure air, with one of the animal kind, occupied the space of eight-tenths of an inch; but when fired by the electric shock, the residuum stood at a little less than half an inch, and this residuum was almost wholly absorbed on agitation with lime-water. By a subsequent trial it was found, that nearly one-half of the animal air used in this experiment was soluble in water. When equal parts of pure and animal air were burned together, a considerable increase of bulk almost invariably took place; and when the animal was to the pure air as 21 to 15, the bulk of the mixture was increased one half. The residuum of the air was inflammable.

10. To investigate the cause of this augmentation of bulk, three measures of animal were mixed with two of pure air; and several strong electric shocks were made to pass through the mixture, but without being able to set it on fire. On adding half a measure more of pure air, it took fire; and the bulk was augmented from .9 to 1.3 inches. Three measures of the residuum were then mixed with three of pure air, and the mixture fired by the electric shock; the bulk of the mixture being reduced from one inch to .56. On agitation with lime-water, two-thirds were absorbed, and the remainder consisted almost entirely of pure air.

Having accidentally taken two or three small shocks through some alkaline air, and not observing any sensible increase of bulk, the Doctor mixed it with an equal quantity of pure air, not apprehending that any decomposition had taken place. Contrary to expectation, however, the two fluids entered rapidly into combination with each other the moment that the electric shock was made to pass through them. The jar, which he held loosely in his hand, as it was inverted over the jar, was carried obliquely upward with great violence; the fland of the prime conductor was broken, and the cylinder shattered into a thousand pieces. The experiment, however, was afterwards falsly repeated with a very strong apparatus; the jar being pressed down with a plate of iron for the purpose of retaining it in its place.

"It appeared (says the Doctor), that when the alkaline and pure air were immediately mixed together, and a small shock was made to pass through them, they would not take fire; but when three or four shocks were previously taken through the alkaline air, and the latter was afterwards mixed with an equal quantity of pure air, they exploded with great violence. One-sixth of the residuum was alkaline, the remainder phlogisticated air."

Several other experiments are related by the Doctor in this paper, which tend to show that animal hepatic air is extricated in large quantity by the process of putrefaction. By distilling a green cabbage leaf, he also obtained an aerial fluid, in most of its properties resembling animal hepatic air. The fetid smell of this gas is destroyed by exposing it to remain in contact with pure air for several weeks; and so effectually by the vapour of dephlogisticated marine acid, that he was induced to try the efficacy of this fluid as an application to cancers. In some cases it appeared to be of service, though some ulcerated cancers were found so irritable, that they could bear no application whatever. The liquid itself appears to be unsafe when taken inwardly. Dr Crawford having taken 20 drops of it largely diluted with water, found himself affected with an obtuse pain and sense of constriction in his stomach and bowels, which resisted the use of emetics and laxatives, but yielded to sulphureous water. He found afterwards, that the manganese which had been used in the distillation of the acid, contained a small quantity of lead. He relates also, on the authority of Dr Ingenhouz, that a Dutchman of his acquaintance some time ago drank a considerable quantity of the dephlogisticated marine acid; the effects it produced were so violent, that he narrowly escaped with his life. These deleterious qualities our author attributes to lead; though it can by no means be proved that manganese is more innocent; and it is also exceedingly probable that some of this femiment rises in the preparation of what is called the dephlogisticated or oxygenated marine acid.

**HEPATIC Aloes**, the inspissated juice of a species of Aloe.

**HEPATIC Stone.** See Liver Stone.

**HEPATIC Water.** See Hepatic Sulphuris.

**HEPATICA,** in botany, a species of Anemone.

**HEPATITIS,** in medicine, an inflammation of the liver. See Medicine-Index.