226 Dr. Wollaston on Cystic Oxide, 
lion from alkaline solutions, are the acetic and citric acids. 
But the tartaric acid may occasion an appearance of precipita- 
tion, by forming a supertartrate with the alkali employed. 
The combination of this substance with acids, may be made 
to crystallize without difficulty, and they form slender spicula 
radiating from a center, wffiich readily dissolve again in water, 
unless they have been injured by being in any degree over- 
heated. 
The muriatic salt is decomposed by the heat of boiling 
water, on account of the volatility of the acid, and the rest 
are easily destroyed by a greater excess of heat. 
The salt formed by combination with nitric acid, does not 
yield oxalic acid, and does not become red, as the uric acid 
does, when similarly treated ; but it turns brown, becoming 
gradually darker, till it is ultimately black. 
When the combinations with alkalies are evaporated, they 
leave small granular crystals ; but as I was desirous of ren- 
dering my experiments as numerous as a limited quantity 
would permit, the portion which I could employ in any one 
experiment was too small for me to attempt to determine the 
form of such crystals. 
When a hot solution in potash was neutralized by distilled 
vinegar, the precipitate did not immediately take place, but 
formed gradually during the cooling of the liquor in minute 
crystals, some at the surface of the fluid, and others attached 
to the sides of the vessel. The only definite form which I 
could observe, was that of flat hexagonal plates, but I could 
discern nothing which enabled me to judge of the primitive 
form of the crystal. On the surface of the calculus belonging 
to Guy’s Hospital, some minute crystals may be discerned, of 
