1835.] on Urine. , 9 



formed doubtless that they may constitute soluble com- 

 pounds, which may be withdrawn from the blood and 

 thrown out of the system by the urine. 



Oxalic acid is a common ingredient in urinary calculi, 

 always I believe united to lime ; and oxalate of lime is said 

 to have been observed in some rare instances deposited 

 from urine under the form of gravel. It is obvious from 

 this that it must sometimes exist in urine, and therefore be 

 secreted or separated from the blood in the kidneys. But 

 I have never myself had an opportunity of examining any 

 urine containing oxalic acid, nor have I even heard of any 

 person who had. 



Small calculi composed of carbonate of lime occur some- 

 times though rarely in man ; but such calculi from the 

 inferior animals are abundant, especially from the horse 

 and cow. This is another reason for admitting at least 

 the occasional presence of carbonic acid in urine. 



The analysis of urine is rather a difficult process, and 

 different specimens differ so much from each other, that it 

 is difficult to give a general view of the constituents that 

 may not in some cases mislead. I shall, therefore, describe 

 an analysis of healthy urine of the specific gravity 1*0185, 

 which I made some years ago. I employed in the analysis 

 11^ cubic inches of urine, or 2957*45 grains ; but for the 

 sake of clearness I have reduced the constituents to what 

 they would have been had I employed only 1000 grains of 

 the urine. 



1 . The urine was mixed with caustic ammonia till it was 

 rendered sensibly alkaline, and left 24 hours in a covered 

 glass jar ; a white precipitate fell, which being collected, 

 washed and ignited, weighed 0*209 grains. It was phos- 

 phate of lime ; for it dissolved without effervescence in 

 nitric and muriatic acids, and was again precipitated by 

 caustic ammonia. 



2. The residual liquid was gently heated to drive off the 

 ammonia and then mixed with a solution of nitrate of lime 

 and left as before for 24 hours in a covered glass jar. A 

 white precipitate fell, which being collected, washed and 

 ignited, weighed 2*01 grains ; it was phosphate of lime, and 

 indicated the presence of 1*131 grains of phosphoric acid 

 in the urine. 



