344 Mr. W. Brande's Observations on the Effects 
water, very highly impregnated with carbonic acid, was taken 
under the same circumstances as in the former experiment, 
and the urine was voided at nearly similar intervals. 
The separation of the phosphates was less distinct, and less 
rapid. In two hours after the urine had been voided, there 
was a small deposit, composed principally of phosphate of 
lime ; there was also a distinct pellicle on the surface, consist- 
ing of the triple phosphate of ammonia and magnesia. This 
appearance, produced by the escape of the carbonic acid, 
which had before retained the ammoniaco-magnesian phos- 
phate in solution, and which now occasions its deposition on 
the surface, is by no means uncommon, even in the urine of 
healthy persons : in the present instance, it appears to prove, 
that carbonic acid passes off from the stomach, by the kidnies, 
for after taking the alkalies in water, very highly impregnated 
with it, the pellicle is uniformly produced, and is also much 
more abundant and distinct, than under any other circum- 
stances. 
In similar experiments with potash, the results were in all 
cases as similar as could be expected in researches of this 
nature. 
Experiment 3. On Magnesia. 
Magnesia was taken under circumstances similar to those 
of the soda in the former experiment : in the quantity of half 
a drachm, it produced no sensible effect upon the urine during 
the whole day. When taken in the dose of a drachm at nine 
o’clock in the morning, the urine voided at twelve o’clock be- 
came slightly turbid : at three o’clock the effect of the magnesia 
was at its maximum, and a distinct separation of the phosphates 
took place, partly in the form of a film, which when examined. 
