as will saturate 10 of oxygen. Now 10 oxygen require 1.327 of hydrogen, and in 49.04 anthrazothionic acid there are 2.19 of hydrogen. Hence 1.327 hydrogen must be contained in 29.71 of acid. The number 29-71, therefore, is the equivalent for anthrazothionic acid; and if from this number we subtract 1-327, or the hydrogen, the remainder 28-39 will be the equivalent for anthrazothion. Future experiments must determine whether anthrazothionic acid will be formed when Lampadius's sulphuret of carbon and ammoniacal gas are made to pass over red hot potash.

ARTICLE III.

On the Sulphuretted Chyazic Acid of Porrett. By M. Vogel.

WHEN Mr. Porrett, an English chemist, was occupied in 1808, with examining the reciprocal action of prussian blue and sulphuret of potash, he discovered sulphuretted chyazic acid

The only set of experiments which has since appeared on this subject is contained in a memoir of M. Grotthuss of Courland.† This chemist made a great number of experiments on this acid and its salts, from which he has drawn as a conclusion that Porrett's acid is not composed of sulphur and prussic acid; but rather of the elements of that acid united to sulphur in very different proportions.

Formation of Sulphuretted Chyazic Acid.

Mr. Porrett has pointed out different methods more or less complicated of obtaining this acid. The method of M. Grotthuss seeming to me to present advantages, I repeated it by calcining in a covered crucible a mixture of two parts of prussiate of potash and one part of sulphur.

The black mass remaining in the crucible being boiled with alcohol of 38 degrees, gave a liquid, colourless after being filtered, which did not form prussian blue with the ferruginous salt, but communicated to them a dark cherry red colour.

The alcoholic solution, however, was very alkaline. Muriatic acid disengaged from it sulphuretted hydrogen gas, and acetate of lead occasioned a black precipitate. Hence it contained potash partly disengaged and partly combined with sulphuretted hydrogen. By M. Grotthuss's method then, we cannot obtain a pure sulphuretted chyazate, nor of consequence pure sulphuretted chyazic acid; for when the salt is mixed with diluted sulphuric acid and distilled, the acid which passes into the retort is contaminated with sulphuretted hydrogen.

* Translated from the Journ, de Pharm. Oct. 1818, p. 441.

+ A translation of this paper has just appeared in the Annals of Philosophy.

The reason why M. Grotthuss's process is unsatisfactory is, that the mixture of prussiate of potash and sulphur is exposed to too high a temperature; for I have ascertained that whenever this mixture is exposed to a red heat, or to the heat of a forge, as Grotthuss prescribes, potash is disengaged, and sulphuretted hydrogen formed. I have, therefore, varied the experiment, and have found that a pure sulphuretted chyazate may be formed by modifying the heat a good deal.

For this purpose, a mixture of equal parts of prussiate of potash and flowers of sulphur is put into a glass matrass, which is exposed to heat. After the matter has ceased to emit air bubbles, it is left for an hour in a state of fusion; but at a temperature greatly below a red heat. The matrass is then allowed to cool, it is broken in pieces, the black matter is reduced to powder, and hot water is poured upon it.* The filtered liquor is colourless, perfectly neutral, and contains no sulphuretted hydrogen. It is not altered when mixed with protosulphate of iron, and becomes red when mixed with persulphate of iron. If the filtered, colourless solution be left exposed for some time to the open air, or if it be placed in contact with nitrous acid in vapour, it becomes dark red, because it contains protoxide of iron combined with sulphuretted chyazic acid and potash. The newly prepared liquid, when mixed with ammonia, allows the green hydrate of iron to precipitate; while prussiate of potash throws down prussian blue.

When the object in view is to obtain sulphuretted chyazic acid, this oxide of iron occasions no obstacle. But if we wish to get a pure sulphuretted chyazate, we must drop into the solution caustic potash till the whole iron is precipitated, The liquid is then filtered while still hot, and evaporated to dryness. The salt obtained is very soluble in alcohol. It does not become red when exposed to the air; but it is very deliquescent, and ought, therefore, to be immediately put into a well stopped bottle. The process for obtaining pure sulphuretted chyazate of potash may, therefore, be reduced to this:

Keep a mixture of equal weights of prussiate of potash in powder and flowers of sulphur in fusion in a matrass for an hour. When the mass has cooled and been reduced to powder, treat it with twice its weight of distilled water, and into the distilled solution drop potash as long as any precipitate falls. Filter a second time, and evaporate the liquid to dryness.

Extraction of Sulphuretted Chyazic Acid.

After having obtained a pure sulphuretted chyazate, it is possible to procure likewise a pure sulphuretted chyazic acid.

*To determine whether the mass has been kept a sufficient time in a state of fusion, and whether all the common prussiate of potash has been decomposed, dissolve a little of it in water, and try the solution with sulphate of iron. If no prussian blue is formed, the decomposition is complete. If it is, we must treat the powder with boiling alcohol, or fuse it a second time.

For this purpose I dissolved an ounce of sulphuretted chyazate of potash in an ounce of water; I poured the solution into a tubulated retort, and added six gros of concentrated sulphuric acid, previously diluted with its own weight of water. The retort having a receiver fitted to it was placed upon a sand bath, and heated.

The product of this distillation is a limpid, colourless liquid. What comes over first contains more water than the succeeding portions. It becomes more and more acid as the process advances. The distillation may be continued as long as the liquid passes over colourless; and this colourless liquid only should be regarded as pure sulphuretted chyazic acid. It ought to be preserved in small bottles, which should be quite filled with it. The liquid which comes over last is yellow, and contains a little sulphur in solution, and sometimes even hydrosulphuret of ammonia. It ought not to be added to the colourless acid.

There remains in the crucible, besides sulphate of potash, a powder of a deep orange colour, containing sulphur and charcoal.*

Properties of pure Sulphuretted Chyazic Acid.

When most concentrated, it is a colourless liquid with a pungent smell, reddening vegetable blues, and having an acid taste. Its specific gravity at the temperature of 61° is 1.0203.

To satisfy myself whether my sulphuretted chyazic acid contained any prussic acid, I super-saturated it with potash, and added to the newly prepared solution protosulphate of iron. But not the least prussian blue was formed, even when an acid was added to the liquid.

Neither does it contain any sulphuric or sulphurous acid; for it is not precipitated by barytes water. The white crystalline precipitate, produced by acetate of lead, is entirely soluble in cold water. This last experiment proves likewise that the acid contains no sulphuretted hydrogen.

Action of Heat on Sulphuretted Chyazic Acid.

The acid requires, when the barometer stands at 28.24 inches, a temperature of 21610, to cause it to boil.

When acid is boiled in a glass filled with mercury, the column of mercury sinks completely, and recovers its former height when the acid is allowed to cool. Hence the acid, when boiled, is converted into vapour, but not into gas.

When the acid is poured into a red hot platinum crucible, sulphur is disengaged, and at last burns with a blue flame.

But no

* I have likewise distilled sulphuretted chyazate of potash with an addition of phosphoric acid, and have obtained very pure sulphuretted chyazic acid. orange powder remains in the retort; and it appears that sulphuretted chyazic acid is not decomposed by phosphoric acid.

I passed the vapour of the acid through a red hot porcelain tube, and obtained at the furthest extremity of it, sulphur, sulphuretted chyazic acid undecomposed, and prussic acid, which was partly saturated with ammonia. But I found no charcoal in the tube; though I have no doubt that if the acid be passed very slowly through a red hot tube, it will be completely decomposed, and will deposit charcoal.

When the acid is passed through a red hot porcelain tube filled with iron turnings, we obtain sulphuret of iron, prussic acid, and sulphuretted hydrogen.

Sulphuretted chyazic acid crystallizes in six-sided prisms at the temperature of 544°.

Action of Air.

When pure concentrated acid is exposed to the air in an open vessel, it soon begins to evaporate. A slip of paper, with which the mouth of the vessel was covered, became red; while the acid assumed a yellow colour, and deposited sulphur.*

Mr. Porrett states that the acid becomes red on the contact of air, and that it is oxydized; but I cannot adopt his opinion. The red colour doubtless proceeded from some protoxide of iron which had passed into peroxide by the contact of the air, or it might, perhaps, have been occasioned by the contact of paper, or other organic bodies floating about in the air. The sensibility of this acid for peroxide of iron is so great that it cannot be filtered through paper, or placed in contact with cork, without becoming red.

Action of Chlorine.

When sulphuretted chyazic acid was mixed with liquid chlorine, this last substance lost its odour and its yellow colour. The mixture was now precipitated by muriate of barytes, which was not the case before. Hence sulphuric acid had been formed; but no sulphur was deposited.

Neither does chlorine precipitate sulphur from the sulphuretted chyazate of potash; though M. Grotthuss has founded a mode of analyzing this acid upon the separation of the sulphur in this case. I have already shown that the sulphuretted chyazate of potash, procured by Grotthuss, by means of a red heat, contained sulphuretted hydrogen. This was the reason why chlorine precipitated sulphur from it.

Sulphuretted chyazic acid is completely decomposed, when agitated with chlorine; for the mixed liquid, after being saturated with potash, is no longer reddened by persulphate of iron. But prussian blue is formed, which is insoluble in muriatic acid. When a mixture of sulphuretted chyazic acid and chlorine is slightly heated, a very distinct odour of prussic acid becomes perceptible, If this vapour is made to pass into lime water, we

* When exposed in small bottles to the rays of the sun, it becomes likewise yellow, and deposits sulphur.

obtain prussiate of lime, which forms prussian blue with ferruginous solutions.

When sulphuretted chyazic acid is poured into a vessel filled with chlorine gas, the temperature rises considerably. The whole of the sulphur is converted into sulphuric acid, and of course no sulphur is precipitated.

Thus it appears that the action of chlorine upon sulphuretted chyazic acid consists in converting the sulphur into sulphuric acid, and setting the prussic acid at liberty. It is necessary to employ a slight excess of chlorine in order to acidify the whole of the sulphur; but if the proportion used be too great, it would combine with the prussic acid when set at liberty.

The opinion of Mr. Porrett, that sulphuretted chyazic acid is a compound of prussic acid and sulphur, is not so absurd as M. Grotthuss conceives it to be; for can it be said that the chlorine formed prussic acid? This would be a thing without example in chemical science.

The sudden death which sulphuretted chyazic acid produces in animals seems still further to favour the notion, that it is not merely the elements, but the prussic acid itself, which acts. It is a most striking fact that prussic acid, when it combines with sulphur, loses its most remarkable properties.

Nitric or nitrous acid does not precipitate sulphur from sulphuretted chyazic acid. All the sulphur is converted into sulphuric acid, and the prussic acid becomes free. Concentrated sulphuric acid is the only acid which precipitates sulphur from sulphuretted chyazic acid.*

Action of Iodine.

When sulphuretted chyazic acid was boiled with iodine, there passed into the receiver, which contained lime water, a quantity of prussic acid. The liquid which remained in the crucible had a reddish brown colour, and was very acid, but did not contain prussic acid. When this liquid was neutralized by ammonia, it became colourless. It was precipitated red by corrosive sublimate; orange yellow by acetate of lead; and green by protonitrate of mercury. The sulphuretted chyazic acid of course had been decomposed, and hydriodic acid formed.

On an analogous Property between Sulphuretted Chyazic Acid and Meconic Acid.

Sulphuretted chyazic acid, when mixed with ferruginous salts, produces exactly the same appearances as meconic acid. Neither of these acids occasions any change of colour in the protosalts; but both of them dissolve the peroxide of iron, and form with it

When I placed sulphuretted chyazic acid in the circuit of a Voltaic battery of 50 pair of plates, I observed at the negative pole a considerable disengagement of gas, while sulphur was deposited round the positive pole,