24,0 Mh W. Brande on the Differences 
If however we attend to what would take place in the body, 
we shall find the circumstances very different. 
That alkaline carbonates and sub-carbonates exert no action 
upon uric acid I consider to be completely established, both by 
the experiments of several eminent chemists, and those I have 
myself made upon the subject ; and as there is at all times a 
quantity of uncombined acid in the urine, it follows that al- 
though the alcali may arrive at the kidnies in its pure state, it 
will there unite with the uncombined acid, and be rendered 
incapable of exerting any action upon the calculus in the 
bladder. Besides phosphoric acid, the urine always contains 
a quantity of uncombined carbonic acid ; this is proved by 
placing a quantity of recently voided urine under the receiver 
of an air pump; during the exhaustion, a large quantity of 
carbonic acid gas makes its escape : and when urine is dis- 
tilled at very low temperatures, carbonic acid gas is given off : 
and also, when lime water is poured into urine, a precipitate 
appears, consisting of phosphate and carbonate of lime. 
Lime water, on account of the insoluble compounds which 
lime forms with carbonic, and phosphoric acids, is even more 
objectionable as a solvent, than the alkalies. 
It may however be said, that if these means prevent the 
increase of a calculus, material relief is afforded to the patient. 
How far the exhibition of alkaline remedies can be recom- 
mended upon these grounds, will appear, when the circum- 
stances which attend the formation of the second species of 
calculous sediment or deposition in the urine, are considered. 
The ammoniaco-magnesian phosphate appears under two 
forms : it is either voided in a solid state, or in solution. In 
the former case it bears a good deal of resemblance to a white 
