422 JDr. Prout’s description of an acid principle 
of water, or any other fluid capable of holding it in solution, 
it sometimes assumes the form of thin pearly scales. 
The purpuric acid is very little soluble in water. One tenth 
of a grain boiled for a considerable time in 1000 grains of water 
was not entirely dissolved. The water assumed a purple 
tint, which it retained after it was cold, though it became 
very slightly turbid on cooling.* The purpuric acid is inso- 
luble in alcohol and ether. In all the mineral acids, when 
concentrated, and in excess, and in solutions of the different 
alkalies, it dissolves readily ; but it is insoluble, or nearly so, 
in dilute sulphuric, muriatic, and phosphoric acids, and also 
in solutions of the oxalic, citric, and tartaric acids. Concen- 
trated nitric acid readily dissolves it with effervescence ; and 
if the acid be in excess, and heat be applied, a portion of the 
purpuric acid is decomposed, ammonia is formed, and on 
driving off the excess of nitric acid by heat, the purpurate of 
ammonia is obtained, precisely as if a little of the lithic acid 
had been treated in a similar manner. Chlorine, likewise, 
dissolves the purpuric acid, and apparently produces the 
same changes upon it as the nitric acid. It readily dissolves 
also by the assistance of heat, in concentrated acetic acid. 
The purpuric acid does not sensibly affect litmus paper, 
probably on account of its insoluble nature. When exposed 
to the air it does not deliquesce, but gradually assumes a 
purplish tint, apparently by attracting a little ammonia from 
* I am not quite sure whether the purple tint here mentioned depends upon the 
actual solution of a minute portion of the purpuric acid j and, consequently, whether 
it naturally forms a purple solution, or whether the colour be owing to the formation 
of a little ammonia from the decomposition of a minute proportion of the acid, which, 
combining with the remainder of the acid, forms the purpurate of ammonia. I 
incline to the latter opinion. 
