tions of the first two ingredients are very nearly reversed. Klaproth obtained from 04 to 05 of copper, and from 0:22 to 0.27 of iron. This renders it obvious, that the two ores were not in the same state. I have little doubt, that the difference, however, is merely apparent, and that it arose, altogether, from a quantity of iron pyrites, and perhaps also of arsenic pyrites, which I could not separate from the gray copper ore which I examined. Both of these minerals could be distinctly seen in many of the specimens, intimately mixed with the gray copper; and I have no doubt, that the same mixture existed, even in those specimens which were selected as purest. The difference in the proportions of copper and arsenic, obtained by Klaproth in his various analyses, is so considerable, as to lead to a suspicion, that even his specimens, in all probability, contained a mixture of foreign matter.

IV.

Researches on the Oximuriatic Acid, its Nature and Combinations; and on the Elements of the Muriatic Acid. With some Experiments on Sulphur and Phosphorus, made in the Laboratory of the Royal Institution. By H. Davy, Esq. Sec. R. S. Prof. Chem. R. I. F. R. S. E.

(Concluded from vol. XXVII, p. 337.) I SHALL occupy the time of the society for a few minutes

only, for the purpose of detailing a few observations connected with the Bakerian lectures delivered in the last two years; particularly those parts of them relating to sulphur and phosphorus, which new and more minute inquiries have enabled me to correct or extend.

I have already mentioned, that there are considerable Differences in differences in the results of experiments made on the action the results of

Gehlen's Jour. vol. V, p. 9, 11, 13.

of

experiments

of potassium on sulphur and phosphorus, and their combion sulphur and nations with hidrogen, according to different circumstances phosphorus. of the process. I shall now refer to such of these circumstances, as I have been fully able to investigate.

Sulphur con

The able researches of Dr. Thompson have shown, that tains an acid, sulphur, in its usual state, contains small quantities of acid matter; and though, in my first experiments, I conceived that by employing crystallized native sulphur, which had been recently sublimed in nitrogen, I should avoid the presence of any foreign matter, yet I am inclined to believe, 1 that this is not the case; for, by sublining some similar sulphur in nitrogen, I find, that litmus paper placed in the upper part of the retort is slightly reddened.

even when sublimed in nitrogen.

Retort must be lined with

sulphur when combining

with potassi.

um.

When potassium is made to unite with sulphur, if the retort employed is not lined with sulphur, some of the potassium is destroyed by acting upon the glass; and when large quantities of sulphur are used, it is very difficult to decompose the whole of the sulphuret of potassium by an Sulphuretted acid sulphuretted hidrogen likewise is soluble in muriatic hidrogen acid; and this circumstance led me to underrate the quanit underrated. tity of sulphuretted hidrogen given off in experiments of this kind.

evolved from

Another er

out.

In acting upon sulphuretted hidrogen by potassium in tour pointed my early experiments, I used large quantities of the gas and of the metal; and in these cases I have reason to believe, that the violence of the combustion occasioned the decomposition of a considerable quantity of the gas; and, in consequence, led me to form erroneous conclusions con-, cerning the nature of this curious operation.'

More accurate

In all late experiments, in which sulphur, or sulphuretted ducting these hidrogen was concerned, I have used inuriatic acid satu

mode of con

* This circumstance has been pointed out by Messrs Gay-Lussac and Thenard, in a paper printed in the Journal de Physique for Decem❤ ber, in which these gentlemen endeavour to show, that, whether potassium has been acted upon by large or small quantities of sulphur, and under all circumstances, it evolves a quantity of gas exactly equal to that which it produces by the action of water. I have been able to gain no results so precise on this subject. I have in another place (the same journal in which their memoir has appeared) offered some observations on their inquiries.

rated

limed from

cuo not acid.

rated with sulphuretted hidrogen over mercury. I have em- experiments. ployed sulphur distilled from iron pyrites in vacuo, which Sulphur subdid not in the slightest degree affect litmus paper, and I pyrites in va have combined it with potassium in retorts of green glass, or plate glass lined with sulphur, and filled with very pure nitrogen or hidrogen. In making potassium act upon sulphuretted hidrogen, I have employed the gas only in the quantities of from 1 to 3 cubical inches, and have made the combination in narrow curved tubes of green glass over

form.

dry mercury. With all these precautions, and after having Results not made a great number of experiments, I am not able to perfectly unigain perfectly uniform results. Yet there is a sufficient correspondence between them, to enable me to form conclusions, which I may venture to say cannot be far from the truth.

When 1 grain of potassium, which would give by the Action of potaction of water about 1 cubical inch and of hidrogen, is assium on sulphur, in small made to act upon about half a grain of sulphur, some proportion, sulphur sublimes during the combination, which always. takes place with heat and light; and from to' of a I cubical inch of sulphúretted hidrogen is evolved. The compound acted on by muriatic acid, saturated with sulphuretted hidrogen, affords from to of a cubical inch of pure sulphuretted hidrogen.

When more sulphur is used, so as to be from twice to and in larger ten times the weight of the potassium, the quantity of sul- proportion. phuretted hidrogen evolved by the action of the acid is from to; but if heat be applied to the combination, so as to drive off the superfluous sulphur, the quantity of gas collected is very little inferior to that produced from the combination in which a small proportion of sulphur is used; and I am inclined to believe, from the phenomena presented in a great number of experiments, that sulphur and potassium, when heated together under common circumstances, combine only in one proportion, in They combine which the metal is to the sulphur nearly as 3 to 1 in weight; only in one proportion, and in which the quantities are such, that the compound burns into neutral sulphate of potash.

When a grain of potassium is made to act upon about Action of pot11 cubical inches of sulphuretted hidrogen, all the hidrogen phuretted his

VOL. XXVIII.—JAN. 1811.

D

is

assium on sul

drogen, in due is set free, and a sulphuret of potassium, containing one proportion; fourth of sulphur, is formed, exactly the same as that produced by the immediate combination of sulphur and the metal.

and in larger proportion.

Potassium

phosphorus only in one proportion.

When sulphuretted hidrogen is employed in larger quantities, there is an absorption of this gas, and a volume is taken up about equal to the quantity of hidrogen disengaged; and a compound of sulphuretted hidrogen and sulphuret of potassium is formed, which gives sulphuretted hidrogen by the action of an acid, nearly double in quantity to that given by the sulphuret of potassium.

From a number of experiments, I am inclined to becombines with lieve, that potassium and phosphorus, in whatever quantities they are heated together, combine only in one proportion, a grain of potassium requiring about of a grain of phosphorus to form a phosphuret; which, when acted upon by muriatic acid, produces from to 4% of a cubical inch of phosphuretted hidrogen.

Action of potassium on phosphuretted

Half a grain of potassium decomposes nearly three cubical inches of phosphuretted hidrogen, and sets free idrogen. rather more than four cubical inches of hidrogen; and the phosphuret formed seems to be of the same kind as that produced by direct combination of the metal with phosphorus.

Weight of an ultimate atom of sulphur de

If, according to Mr. Dalton's ideas of proportion, the quantity in which sulphur enters into its combinations were duced from its to be deduced from its union with potassium, in which it compounds. seems to form about the weight of the compound, the number representing it would be 13.5. I have lately weighed sulphuretted hidrogen, and sulphureous acid gas, with great care the specific gravity of the first at mean temperature and pressure, from my experiments, is 10645, which differs very little from the estimation of Mr. Kirwan: that of sulphureous acid gas I find is 20967. Sulphuretted hidrogen, as I have shown, contains an equal volume of hidrogen; and on this datum the number representing sulphur is 13.4. I have never been able to burn sulphur in oxigen without forming sulphuric acid in small quantities; but in several experiments I have obtained from 92 to 98 parts of sulphureous acid from 100

Sp. grav. of eulphuretted hidrogen and sulphureous asid gas.

of

of oxigen in volume; from which I am inclined to believe, that sulphureous acid consists of sulphur dissolved in an equal volume of oxigen; which would give the number as 13.7* nearly, considering the acid gas as containing 1 portion of sulphur, and 2 of oxigen; and these estimations do not differ from each other materially.

I have made several experiments on the combustion of Weight of an phosphorus in oxigen gas. From the most accurate, I am ultimate atom of phosphoinclined to conclude that 25 of phosphorus absorb in com- rus. bustion about 34 of oxigen in weight; and considering phosphoric acid as composed of 3 proportions of oxigen and 1 of phosphorus, the number representing phosphorus will be about 16.5, which is not very remote from the number that may be deduced from the composition of phosphoret of potassium.

bined in them,

The numbers, which represent the proportions in which Sulphur and phosphorus sulphur and phosphorus unite with other bodies, are such, may contain as do not exclude the existence of combined portions of oxigen and hioxigen and hidrogen in their constitution; but it may be drogan comquestioned, whether the opinion which I formed, that the inflammable gas disengaged from them by electricity is necessary to the peculiar form in which these bodies exist, is not erroneous. Phosphorus, as I have stated in the last Bakerian lecture, is capable of forming a solid hydruret: and a part of the sulphur distilled from iron pyrites is usually of a soft consistence, and emits the smell of sulphuretted hidrogen, and probably contains that body. It and probably is not unlikely, that in all cases phosphorus and sulphur in no case perfectly free

The estimation from the composition of sulphuretted hidrogen must be considered as most accurate, and that from the formation of the sulphuret of potassium as least accurate: for it was only by combining sulphur and potassium in small proportions, and ascertaining in what cases uncombined sulphur could be distilled from the compound, that I gained my conclusious concerning the composition of the sulphuret of potassium.

In the last Bakerian lecture, I have estimated the specific gravity of sulphuretted hidrogen at $5 grains the 100 cubical inches, which was not far from the men, between the estimations of Mr Kirwan and Mr Thenard. According to this experiment, sulphuretted hidrogen is composed of 1 portion of hidrogen, represented by 1, and 1 of sulphur represented by 13 4.

D2

contain