23 ° Mr. W. Brande on the Differences 
Sixty grains of another calculus of a considerable size, sup- 
posed from a superficial analysis, to consist of nearly pure 
urate of ammonia, were digested at a low temperature in one 
ounce of alcohol. In an hour the alcohol was decanted off, 
and fresh portions were added successively, as long as it ap- 
peared to act upon the calculus, which after having been care- 
fully dried in a temperature below 212 0 , weighed 54,-8. grains, 
so that 5.2 grains had been taken up by the alcohol. 
On evaporating the alcoholic solutions, a substance was 
obtained having all the properties of urea, with a small por- 
tion of saline matter, probably muriate of ammonia, as by the 
addition of potash, a slight ammoniacal odour was perceptible ; 
its quantity however was too minute for accurate examination. 
The remaining portion of the calculus, weighing 54.8 
grains, was treated with small portions of acetic acid, by 
which 6 . grains of the ammoniaco-magnesian phosphate were 
obtained. 
The part of the calculus remaining after this treatment, 
weighing 48.8 grains was perfectly soluble in a solution of 
pure potash ; it emitted no ammoniacal odour when acted upon 
by the alcali, and possessed the properties of pure uric acid. 
The following therefore is the composition of this calculus. 
Grains. 
Urea, and muriate of ammonia - - 5.2 
Ammoniaco-magnesian phosphate - 6 . 
Uric acid - - - 48.8 
60. 
From these and many similar experiments upon other cal- 
culi, hitherto generally supposed to consist of urate of am- 
