150 ~~ Professor Dana on Morbid Animal Products. 
1. Examination of calculi containing Urate of Ammonia. 
Externally of a very light clay colour, or nearly of the 
wine yellow of Werner, internally of the same colour with 
a nucleus of a reddish hue; form, rounded and flattened on 
two or more sides ; size, from that of a large pea to that of 
a filbert ; appeared to be composed of nies layers, 
some of which had the reddish tinge of the n 
Water in which these calculi have been boiled, ‘deposits 
on cooling, a great number of small brilliant erystals, which 
are uric acid ; the liquor was separated from the crystals by 
a filter, and to it was added a few drops of the solution of 
potash, ammonia was disengaged and was not only evident 
by forming a cloud with muriatic acid, but also by the 
sme 
A strong odour of ammonia is evolved when a small 
quantity of the powdered calculi is rubbed in a mortar with 
caustic soda. 
_ Nitrate of silver added to the watery solution produces a 
ipitate, which differs in appearance from that produced 
aoe ticacid ; this precipitate was not soluble in water of 
pure ammonia ; when boiled to dryness in nitric acid, gave 
a pink coloured residuum, and when placed on platina foil, 
and exposed to the heat of a spirit lamp, the silver is reduced 
to its metallic state at a heat below redness ; this fact is not 
mentioned in any of the chemical authors which I possess, 
but I suppose that it cannot have ceckped the notice of Dr. 
Henry, in his researches upon the urates. These experi- 
ments are sufficient to prove that it is an an rat and not a 
muriate of silver which was precipitated. 
hol, separates from these calculi a Fail quantity of 
poe Eight grains of this calculus in fine powder were diges- 
ted in a large quantity of distilled water, and the solution, 
when cold was filtered. 
2. To the clear liquor was added a solution of nitrate of 
silver as long as it produced a precipitate ; the whole was 
rown on a filter, tipi well washed with 
water. The precipitate was of a yellowish colour, but 
e black when dry, exhibiting a close texture and a 
smooth resinous fracture, it weighed 3.85 grs. 
3. The precipitate being exposed to heat on platina foil, 
