1 1 8 ORGANIC NITROGEN O US MANURES 



cent.) caustic soda, free ammonia is liberated from the 

 ammonium salts and the amides present, and the 

 ammonia may be recognised in the usual way. 



Protein Material — The material remaining after 

 heating the dung with dilute soda and driving off all 

 the loosely combined nitrogen, is dried and heated in 

 a tube with soda-lime, when more ammonia will be 

 produced, showing the presence of complex nitrogenous 

 bodies. 



{U) Phosphoric Acid and Potash. — Twenty to 30 

 grams of the manure are extracted by boiling with 

 hydrochloric acid. The solution is filtered, and the 

 potassium salts and phosphates may be recognised in 

 the filtrate by the usual tests. 



{c) Humus. — If this has not already been done 

 (p. 60), humus should be prepared from well-rotted 

 manure by the method already described {loc. cit.). 



Liquid Excrement. 



The urine of animals, which is largely absorbed by their litter 

 and is thus a constituent of fresh farmyard manure, is one of the 

 latter's most valuable constituents. It contains simple nitrogen 

 compounds like urea, uric acid, and ammonia, as well as soluble 

 phosphates and potassium salts, the various constituents being 

 almost ready for plant nutrition and requiring but slight further 

 changes actually to become so. The concentration of the liquid 

 excrement of the various animals in manurial constituents increases 

 in the order — pig, sheep, cow, horse. 



101. Separation of Urea from Human Urine. 



Urea, CO(NH2)2, the most important constituent of 

 urine is prepared from it as follows : — About 2 litres of 

 urine, containing about 30 to 40 grams of urea, are 

 evaporated down to small bulk (200 or 300 c.c), 

 allowed to cool, and mixed with 50 c.c. of nitric acid. If 

 no precipitation occurs the liquid is further evaporated 



