1819.] — Mr. Porrett on Sulphuretted Chyazic Acid. 359 
triple prussiates, in the Philosophical Transactions for 1814, I 
stated that from five gr. of sulphuretted chyazate of copper, 
decomposed by nitric acid, I had obtained, by means of iron, 
2-82 gr. of metallic copper, which, reckoned as protoxide, is 
equal to 3-173 gr. or to 63°44 per cent. 
I have since found that this determination was not quite accu- 
rate, the quantity of copper having been overstated by about 1d 
of a grain ; the true quantity is 2°45 gr. equal to 2°75 of protox- 
ide, or to 55 per cent. Therefore sulphuretted chyazate of 
protoxide of copper is composed of 
ACIG, paccurce S40! dese. S008 =' atom 
Wage. 45, «asc alte Db o éé& ele oe, «90500 =. 1 atom 
100 163-94 = 1 atom 
In the same paper it will be seen, that by acidifying the sul- 
hur in five gr. of the above compound, and adding a salt of 
Seeiee, I had obtained 8°86 gr. of sulphate of barytes represent- 
ing 1-20 gr. of sulphur; on repeating this experiment with all 
imaginable care, I have obtained about 1th of a grain more, the 
quantity being 9 gr. equal to 1:22 sulphur. Von Grotthuss, who 
also repeated this experiment, obtained only 8-1 gr. ; but he has 
certainly underrated it. 
Now as 5 gr. of this compound contain 1:22 gr. of sulphur, 
100 must contain 24-4, and this deducted from 45, leaves 20°6 
gr. as the weight of the other constituents of the acid in 100 gr. 
of the sulphuretted chyazate. These other constituents I have 
long since stated to be the elements of prussic acid in the propor- 
tions in which they exist in that acid; and notwithstanding Von 
Grotthuss’s denial of this statement, I must be allowed to per- 
sist in it; an experiment which I shall presently describe will 
fully justify me in so doing. 
We have it now in our power to state the constituents of sul- 
phuretted chyazate of copper more in detail, as follows: 
IS eR ER eae 24:4.. 40:00 = 2 atoms 
Carbon, azote, and hydro- 
gen, in the proportions 
which form prussicacid 20°6.. 33:94 = 1 atom of prussic acid 
Sulphuretted chyazic acid 45°0.. 73-94 = latom 
?rotoxide of copper .... 55°0,.. 90°00 = latom 
——— —Ee 
100:0 163°:94 = ] atom 
3ut in order to put the composition of this salt and of its acid 
outof all doubt, [ undertook the analysis of it by combustion 
with peroxide of copper; for this purpose 1 mixed 4°8 gr. of it 
mtitately by trituration with 12 gr. of the peroxide, the mixture 
was pit into a glass tube made to answer as a small retort, and 
