64 PRACTICAL AGRICULTURAL CHEMISTRY [211-215 



TESTS FOR CARBON, NITROGEN, CHLORINE, 

 AND SULPHUR IN ORGANIC COMPOUNDS 



CARBON (C).— Use sugar. 



211. Heated on platinum foil, carbonaceous substances 

 generally blacken, from the separation of carbon. On con- 

 tinued heating the black substance burns away. 



212. Copper Oxide (CuO), when heated with any 

 substance containing carbon, sets free carbon dioxide. To 

 perform this experiment mix a little sugar with three times 

 its bulk of copper oxide and place at the bottom of a dry 

 test-tube ; cover with a little CuO. Fit a tube bent twice 

 at right angles through the cork ; let this tube dip into 

 another test-tube containing lime-water, and heat the mix- 

 ture. The lime-water will become milky. 



NITROGEN (N).— Use urea, CO(NH 2 ) 2 . 



213. Soda-lime, on heating with most nitrogenous 

 substances, liberates ammonia, which may be recognised 

 by its smell and its action on turmeric-paper. 



214. Sodium (Na) forms sodium cyanide when heated 

 in a test-tube with most organic nitrogenous substances. 

 On extracting with water, filtering, and adding a solution of 

 ferrous sulphate containing a drop of ferric chloride and 

 finally hydrochloric acid in excess, a precipitate of Prussian 

 blue is left. 



CHLORINE (CI).— Use chloral hydrate. 



215. Lime (CaO) when heated in a test-tube with an 

 organic-chlorine compound forms calcic chloride (CaCl 2 ). 

 On dissolving in dilute nitric acid (HN0 3 ), filtering, and 

 adding silver nitrate (AgN0 3 ), a white precipitate is formed. 



