152 Professor Dana on Morbid Animal Products. 
By the theory, urate of silver, containing six proportions 
of acid, consists of 
6 atoms uric acid 26 x6=156 
1 atom oxide silver - - 118. 
My analyses gives uric acid - - 157.33 
oxide of silver 118— 
Urate of ammonia, by the theory consists of 
Uric acid, (6 proportions 26 x6) 156 
Ammonia, 1 proportion - - - 17 
My analysis gives, uric acid, 156.4 and ammonia, 17 
I regret that circumstances would not permit me to ex~ 
amine a larger quantity of these calculi; they will not be 
distinguished from uric acid by the general tests proposed 
by Dr. Marcert, for the detection of this substance, for they 
are totally volatile before the blowpipe, and give a pink col- 
oured residuum with nitricacid; their colour, and the odour 
of ammonia developed by an alkali will distinguish them 
from uric acid calculi ; the effect of heat on the precipitate 
they afford by nitrate of silver, is sufficient to distinguish 
them. 
2, Examination of some concretions found ina box, labelled 
“ Coneretions growing in a Parrot, from Dr. Oliver, 
1759” in the Nichols collection. 
Colour light grey, form irregular, rounded ; smooth to 
the touch ; splintery fracture; hard; cut without difficulty 
by the knife, and exhibit a wax yellow colour internally. 
1. Exposed to heat, evolve an odour resembling that of 
burning bread; by continuing the heat, the odour becomes 
like that of burning feathers; a bulky charcoal of difficult 
incineration remains. When exposed to the flame of a spirit 
lamp, they take fire and burn with a bright light. 
2. Sulphuric acid is blackened by them, and by the aid 
of heat it chars them; diluted sulphuric acid dissolves 
them, and the surface of the solution becomes oily on the 
addition of ammonia. 
3. When digested in acetic acid, they become pulpy and 
transparent, and increased in bulk, and are dissolved in 
part. The acetic acid solution affords a white precipitate 
by prussiate of potash, hence these concretions consist of 
