222 Mr. Porrett’s experiments relative to the 
in the hydroguretted sulphurets, of converting the prussic 
acid at the moment they detach it from prussiate of mer- 
cury, into sulphuretted chyazic acid ; which being much 
less volatile, and having a stronger attraction for alkaline 
bases than the prussic, could not escape from the liquid, 
and would give me the quantity of prussic acid it repre- 
sented, by deducting from its weight, that of the sulphur 
which I knew to exist in it. I therefore dissolved 10 grains of 
prussiate of mercury in hot water, and poured hydroguretted 
sulphuret of soda into the solution until it no longer occa- 
sioned a black precipitate. This black precipitate when dry, 
weighed 9.3 grains ; to the liquid from which it was separated, 
I added a few drops of diluted sulphuric acid ; these caused a 
separation of a minute quantity of sulphur, which was got rid 
of by subsidence, after which I poured into it an aqueous 
solution of the two sulphates of copper, and of black oxide 
of iron, in which the former salt was to the latter by weight, 
as 2 is to 3, until no farther effect was produced. By these 
means I threw down the whole of the sulphuretted chyazic 
acid contained in the liquid, and collected it combined with 
protoxide of copper, in the form of an insoluble white salt, 
which weighed 9.7 grains. 
But as 100 grains of this salt contain 40.62 grains of sul- 
phuretted chyazic acid, composed of 26.39 sulphur and 14.23 
prussic acid, according to my analysis, Phil. Tran, for 1814, 
page 549, Exp. C, (corrected by calculations in the Table 
facing page 230 of the present paper), therefore the before 
mentioned 9.7 grains represent 1.38 of prussic acid, which 
according to this experiment is the quantity existing in 
10 grains of prussiate of mercury. 
