A Memoir on the Uric Acid. 399 
According to Dr. Pearson, the acid is soluble 
in only 800 times its weight of water; and 
Scheele states the quantity required at still 
less, viz. 300 parts. It is to be observed, how- 
ever, that Scheele employed, for his expe- 
riments, only the pulverized calculus, and 
not the purified acid. 
4. The watery solution reddens the infusion 
of litmus, but produces no change on the 
solution of alkaline carbonates. . 
5. When a small portion of the dry acid 
is heated on a bit of window glass with a few 
drops of nitric acid, and the mixture is eva- 
porated to dryness, the residuum has a beau- 
tiful red colour. The addition of a few drops 
of water greatly increases its intensity ; and 
occasions it to resemble that of carmine. This 
colour is communicated to the skin, to wood, 
nd to other animal and vegetable substances. 
It is also soluble in water, and the solution 
has the hue of an acidulated infusion of rose 
leaves; but soon loses it and becomes limpid, 
even when secured from the access of air. The 
colour is destroyed by all acids, and by pure 
alkalis; and is not restored again by any che- 
mical agent which I have employed with this 
view. Fourcroy (p) ascribes this charac- 
(p) Systéme, 4to. V. 516. 
