prepared from the liihic or uric acid . 423 
the atmosphere, or perhaps from the evolution from itself of 
a little of the same alkali by spontaneous decomposition. 
Submitted to heat, it neither melts nor sublimes, but 
acquires a purple hue from the formation of ammonia, and 
afterwards burns gradually, without yielding any remarkable 
odour. Subjected alone to heat in close vessels, it yields a 
considerable proportion of the carbonate of ammonia, some 
prussic acid, and a little fluid having an oily appearance; 
while a portion of pulverulent charcoal remains. When 
given quantities were burnt with the oxide of copper, in the 
manner formerly described by me,* data were obtained, 
which appeared to show that one hundred parts consist of 
Hydrogen 4.54 corresponding with 2 atoms or proportions. 
Carbon 27.27 — — 3 ditto. 
Oxygen 36.3 6 — 2 ditto. 
Azote gt-Si — — — 1 ditto. 
The purpuric acid combines with the alkalies, alkaline 
earths, and metallic oxides. It is capable of expelling the 
carbonic acid from the alkaline carbonates, by the assistance 
of heat, and does not, as far as I have observed, combine 
with any other acid. These are circumstances sufficient, as 
Dr. Wollaston has observed, to distinguish it from an oxide, 
and to establish its character as an acid. On the supposition 
then, that it be named the purpuric acid , its compounds with 
different bases must be denominated purpurates : on some of 
the most remarkable of which I shall now proceed to make 
a few remarks. 
Purpurate of ammonia. This salt crystallizes in quadran» 
gular prisms, which, when viewed by transmitted light, are 
* See Medico-Chirurgical Transactions, vol. ?iii, p. 526. 
