106 76. BASES AND ACIDS WITH REAGENTS. 



cipitated acid on a dried and weighed filter, and add 0.045 

 mgr. to the amount of uric acid found, for every cubic 

 centimetre of wash-water passed through the filter. 



If hippuric acid was present, it must be dissolved out 

 of this precipitate by treating it several times with alco- 

 hol of 83" |„. 



HIPPURIC ACID. HC^H^NOa. 179. 



76. This acid is slightly soluble in cold water, but 

 readily soluble in boiling water and in alcohol, and slight- 

 ly soluble in ether. 



Ferric and plumbic hippurates are quite insoluble in 

 water ; all others are soluble. 



QuantitatiTC estimation* — Precipitate the concentrated 

 solution of the acid with hydrochloric acid, and let the 

 mixture stand in the cold 48 hours ; collect the precipitate 

 on a dried and weighed filter, wash it with small portions 

 of very cold water, until the washings are colorless and 

 give only a faint turbidity with argentic nitrate, dry at 

 100°, and weigh. For every 6 c.c. of wash-water that 

 passed through the filter add 0.01 grm. to the amount of 

 hippuric acid found. 



If uric acid is present, the precipitate, after being 

 weighed, must be treated with alcohol, and the residue of 

 uric acid weighed again. The difference between the two 

 weights will be the hippuric acid. 



For a better method of separating the two acids see 

 urine, § 113, A. 



TANNIC ACID. 



77. Tannic acid is soluble in water, alcohol, and ether; 

 alkaline tannates are soluble in water, but others are diffi- 

 cultly soluble. 



Reactions. — Tannic acid gives a violet-black precipi- 



