URIC ACID, URATES, ETC. 



105 



ammonium benzoate are given off. The latter is decom- 

 posed, giving the odour of ammonia, while there is an 

 aromatic odour of oil of bitter almonds. 



(6.) Examine the colourless four-sided prisms with the 

 microscope (Fig. 28). 



7. Preparation of Hippuric Acid. Take 100 cc. of cow's urine, 

 and evaporate it to one half its bulk ; add hydrochloric acid, and 

 set it aside. The brown mass is collected, dried between folds of 

 blotting-paper, re-dissolved in a very small quantity of water, 

 and mixed with charcoal, then filtered and set aside to crystallise. 



8. Creatinin (C 4 H 7 lSr 3 0) is a derivative of the creatin of muscle. 

 If creatin be boiled with acids or with water for a long time, it 

 loses water, and becomes converted into a strong base creatinin. 



Fig. 29. Creatinin-zinc-chloride. a, Balls with radiating marks; b, crystal- 

 lised from water ; c, rarer forms from an alcoholic extract. 



Quantity, 0-5 to 1 gramme (7 to 15 grs.) It is easily soluble in 

 water and alcohol, and forms colourless oblique rhombic crystals. 

 It unites with acids, and also with salts, chiefly with ZnCl 2 ; the 

 ereatinin-zinc-chloride is used as a microscopic test for its pre- 

 sence. It rarely occurs as a deposit, and nothing is known of its 

 clinical significance. 



