TENDENCY TO CALCULOUS DISEASES. 
75 
takes place, with equal freedom, after the muriate of ammonia has been with- 
drawn from it, as before. I would also add, that on heating dilute muriatic 
acid on the calculus, from which muriate of ammonia has been withdrawn by 
distilled water, muriate of ammonia is formed, by the union of such muriatic 
acid, with the ammonia which is in combination with the lithic acid in the cal- 
culus ; an increase in the weight of the calculus, when thoroughly dried, is 
found to have taken place; and the newly formed muriate of ammonia, is freely 
given up to distilled water. It is not only cognizable by its mode of crystalli- 
zation, but by its ready sublimation ; by the extrication of ammonia from it by 
pure potash ; by the deposition of triple phosphate on the addition of magnesia 
and phosphoric acid ; and the formation of luna cornea, through the means of 
its muriatic acid, on the addition of nitrate of silver. 
The existence of muriate of ammonia in lithate of ammonia calculi, led me 
to inquire, whether, as that substance is always found in urine, some portion of 
it may not insinuate itself into the other species of calculi, and not be an 
attendant on lithate of ammonia alone. On examining various urinary con- 
cretions with a view to this point, I have always found that muriate of am- 
monia is distinctly traceable in common lithic acid. It likewise exists in 
calculi of the mixed phosphates, and in those of oxalate and phosphate of lime; 
and is also capable of being detected in that very rare species of calculus, the 
cystic oxide*. The quantity, however, is exceedingly minute ; but though 
perfectly sensible to appropriate re-agents, it is incapable of being detected by 
any development of ammonia which pure potash can render evident, either to 
the senses or to vegetable colours. 
From these circumstances I am disposed to infer, that the ammonia by 
which so many of the lithic calculi are distinguished, which have come under 
my notice, is usually in actual combination with lithic acid, and does not arise 
* The distilled water which takes up muriate of ammonia from calculi, withdraws likewise a certain 
portion of the lithic acid, or lithate of ammonia, from which hardly any calculus, except, perhaps, the 
cystic oxide, is altogether free. The peculiar crystallization in which the cystic oxide is disposed to 
be thrown down, in combination with the triple crystals, (when the latter are produced by the ad- 
dition of magnesia and phosphoric acid to water, which has been boiled over that curious substance,) 
may render the existence of the triple crystals a little doubtful. On dissolving the latter, however, 
by acetic acid, which does not touch the cystic oxide, the triple crystals become apparent on the ad- 
dition of carbonate of ammonia. 
L 2 
