£6 PRACTICAL AGRICULTURAL CHEMISTRY [222-227 



If organic matter is present the following additional 

 tests should be performed : — 



224. Carbon. — Heat with CuO (212). Evolution of 

 CO 2 shows presence of carbon. 



225. Chlorine. — Heat with lime (215), dissolve in 

 dilute HNO3, an d test with AgN0 3 solution ; a white pre- 

 cipitate indicates presence of chlorine. 



226. Sulphur. — Heat with dilute hydrochloric acid 

 and KCIO3 (216) ; filter, and add BaCl 2 solution ; a white 

 precipitate shows presence of sulphur. 



22TJ. Nitrogen. — If ammonium salts are absent (221) 

 heat the substance with soda-lime ; the evolution of 

 ammonia gas (213) indicates organic nitrogen. 



If ammonium salts are present heat the substance with 

 KHO solution until ammonia gas ceases to be evolved ; 

 filter, mix the residue with soda-lime, and heat in an 



