1819.] Sulphuretted Chyazic Acid. 103 
For this purpose I dissolved an ounce of sulphuretted chy- 
azate of potash m 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 con- 
tains a little sulphur in solution, and sometimes even hydrosul- 
phuret ofammonia. 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 pun- 
gent smell, reddening vegetable blues, and having an acid taste. 
Its specific gravity at the temperature of 612° 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 2161°, 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. 
* T have likewise distilled sulphuretted chyazate of potash with an addition of 
phosphoric acid, and have obtained very pure sulphuretted chyazic acid. Butno 
orange powder remains in the retort; and it appears that sulphuretted chyazic 
acid is not decomposed by phosphoric acid. : 
