of Magnesia in Calculous Complaints. 143 
With a view to ascertain their comparative effects on 
healthy urine, when taken under the same circumstances, the 
following experiments were made. 
Experiment j. On Soda . 
Two drachms of subcarbonate of soda were taken on an 
empty stomach at nine o'clock in the morning, dissolved in 
three ounces of water, and immediately afterwards, a large 
cup of warm tea. 
In six minutes, about one ounce of urine was voided ; in 
twenty minutes six ounces more ; and after two hours, a 
similar quantity. 
The first portion became very turbid, within ten minutes 
after it had been voided, and deposited a copious sediment of 
the phosphates, in consequence of the action of the alkali upon 
the urine. It slightly restored the blue colour to litmus paper 
reddened with vinegar : the alkali therefore, was not merely 
in sufficient quantity to saturate the uncombined acid in the 
urine, and consequently to throw down the phosphates, but 
it was in excess, and the urine was voided alkaline. 
The urine voided after twenty minutes, also deposited a 
cloud of the phosphates, but the transparency of that voided 
two hours after the alkali had been taken, was not disturbed. 
Here, therefore, the effect of the alkali upon the urine, was 
at its maximum, probably in less than a quarter of an hour 
after it had been taken into the stomach, and in less than two 
hours, the whole of the alkali had passed off. 
Experiment 2. On Soda, with excess of Carbonic Acid. 
The same quantity of soda, dissolved in eight ounces of 
