§ 113. URINE. 221 



Estimate the amount of sodic chlorine or of chlorine on 

 the basis of the standard of the solution already determ- 

 ined (§ 86). 



2. TJrea. — In a second portion of 15 c.c. of the liquid, 

 proceed to determine urea with tlie same standard solution 

 (§ 86). Subtract from the total amount of standard so- 

 lution required the amount used in 1, and also make the 

 correction required for dilution of the solution. 



h. Hippuric acid. — Evaporate 200 c.c. of the urine 

 down to 50 c.c, and precipitate the acid as directed in § 

 76. It may be well to first digest the urine with animal 

 charcoal in the proportion of 2 grms. of charcoal to 10 c. 

 c. of the liquid, in order to decolorize it. 



There are usually only traces of uric acid in the urine 

 of herbivora, and it need not be estimated ; but in the 

 urine of carnivora, the proportion of uric acid generally 

 exceeds that of the hippuric. 



According to the process of Meissner and Shepard, for 

 separating these two acids, evaporate the urine until it be- 

 gins to crystallize, add so much absolute alcohol to the hot 

 liquid that a further addition causes no more precipitation, 

 let the mixture cool, and filter it ; the best absolute alcohol 

 must be used, and it must not be spared, else succinic 

 acid may remain in solution with the hippuric and cause 

 trouble. Evaporate the alcoholic solution, at first in a 

 flask on the water-bath, until all the alcohol and the water 

 are expelled and only a brown syrup remains, that solidi- 

 fies to a crystalline mass on cooling ; extract this mass, 

 while yet warm and liquid, with ether and a few drops of 

 hydrochloric acid added after the ether, agitate the mix- 

 ture violently, and repeat the process two or three times 

 with fresh portions of ether. If the alcohol and water 

 were not carefully removed in the preceding evaporation, 

 some of the urea will pass into this ethorial solution. 



Collect all the etherial extracts, distil off most of the 

 ether, and let the rest evaporate spontaneously in the air. 



