termed triple Prussiates, 551 
combined with any sulphur. That sulphur existed in this acid, 
both before and after this experiment, was however proved, 
by heating it in a mixture of nitric acid with muriate of barytes, 
by which means sulphate of barytes was quickly formed and 
precipitated. 
From these analytical experiments on the red tinging acid, 
it appears to me that the following inferences may be drawn, 
1st. That this acid contains sulphur. ABCDEG. 
sdly. That this sulphur constitutes two-thirds of the weight 
of the dry acid. C. 
3dly. That it exists in it, not as a foreign body in solution, 
but as an element. FG. 
4thly. That when the sulphur is acidified, the other consti- 
tuents of this acid unite in the form of Prussic acid, and that 
therefore they consist of the same elements as that acid. DE. 
The results of these analytical experiments shew clearly 
why, in the synthetical ones, the presence of sulphur for form- 
ing it from Prussic acid was indispensible ; they do not how- 
ever so obviously shew why, besides the sulphur, the presence 
of both hydrogen and an alkali are requisite ; probably the 
use of the hydrogen is to bring a sufficient quantity of sulphur 
into a state in which it is soluble in the alkali, while that of 
the alkali, by virtue of the mysterious power often termed 
disposing affinity, favours the formation of the stronger or red 
tinging acid, in consequence of its having a greater attraction 
for it than for the weaker Prussic. 
I shall now drop the term red tinging acid, used merely in 
relating these experiments to avoid anticipating its nature, and 
having, as I think, proved that this acid is composed of sul- 
phur and of the same elements as the Prussic acid, and that 
4 B 2 
