362 Mr. Porrett on Sulphiretted Chyazic Acid. (Mav; 
sulphuretted chyazic acid in combining with nine atoms of oxy- 
gen forms two atoms of sulphurous acid, two atoms of carbonic 
acid, one atom of water, and relinquishes one atom of azote. 
The formation of ammonia in liquid sulphuretted chyazic 
acid by the action of concentrated acids, and considered by 
Von Grotthuss as proving that the azote and hydrogen exist in 
it in the ratio of one to three, proves no such thing. I have 
often observed this formation; it never takes place without the 
simultaneous production of carbonic or sulphurous acid : hence 
in these instances water is decomposed which supplies the addi- 
tional hydrogen requisite. to form ammonia with the azote and 
hydrogen of the acid, and gives up a corresponding proportion 
of oxygen to the carbon or sulphur. 
I felt much surprise at Von Grotthuss’s confident denial of the 
production of prussic acid from sulphuretted chyazic acid, which 
I had asserted to take place when its sulphur is acidified. This 
production is so abundant not only in the cases in which | 
described it as occurring, but ina variety of others, as M. Vogel 
has since proved, that it is quite extraordinary that M. Grotihuss 
did not perceive it. . 
But as one mistake requires others to support it, so I find 
M. Grotthuss asserting, that “as Porrett did obtam prussic 
acid, there can be no doubt that he operated on a salt containing 
a prussiate mixed with it, which would be more readily the case 
as he employed no alcohol, nor indeed any method whatever, to 
separate sulphuretted chyazate of potash from the prussiates.” 
Now it so happens, that it was by the employment of alcohol 
that I first obtained the salt in question, as may be seen by refe- 
rence to the paper in which I announced its discovery, and 
which was published in the Transactions of the Society of Arts 
for 1809; and as to my not employing any other method of 
separating the prussiates, I beg to refer chemists to the follow- 
ing directions, which forma part of the process published in the 
Philosophical Transactions for 1814; and the object of which 
was to separate the prussic from the sulphurettec chyazic acid 
by taking advantage of the greater volatility of the former : 
“Let the clear liquor (containing the two acids united to 
potash) be brought to a decidedly acid state by the addition of 
sulphuric acid; then keep it for a short time at nearly the boil- 
ing point.” 
It is unnecessary to point out any further inaccuracies of 
M. Grotthuss on this subject, especially as some of them have 
been already noticed in M. Vogel’s paper on sulphuretted chya- 
zic acid. This. chemist has besides given an improvement on 
Von Grotthuss’s process for obtaining sulphuretted chyazate of 
potash. Ihave repeated the process in the mode recommended 
by M. Vogel, which I find to answer the purpose exceedingly well ; 
itappears, however, to be still susceptible of advantageous modifi- 
cations: one of these | consider to be a reduction of one quarter 
