40 PRACTICAL AGRICULTURAL CHEMISTRY [104-106 



When quite dry, remove the substance from the filter-paper 

 to a mortar, and there mix it with about three times its 

 weight of soda-lime. Heat some of this mixture in an 

 ignition-tube and test the evolved gases with turmeric-paper. 

 A brown coloration given to the paper indicates organic 

 nitrogen. The reason for the preliminary washing with 

 water is to remove any sulphate of ammonia or other sub- 

 stance which might contain ammoniacal nitrogen. 



* 104. Test for Ammoniacal Nitrogen.— Warm a 

 little of the manure in a test-tube with caustic-potash 

 solution ; test the vapour which comes off with turmeric- 

 paper as directed in paragraph 86. Should the paper turn 

 brown, ammonical nitrogen is present in the manure ; and 

 since sulphate of ammonia is the principal substance in 

 manures which contain nitrogen in this form, we may 

 usually assume that the brown coloration indicates that 

 sulphate of ammonia was present in the manure. 



* 105. Testfor Nitric Nitrogen.— Nitric nitrogen is 

 generally added to manures in the form of nitrate of soda, 

 but many natural manures contain nitrate of lime. This is 

 especially the case with bat's guano. For this test use the 

 clear liquid saved from paragraph 103. Follow out exactly 

 the test described in paragraph 87. Should the indigo be 

 bleached the manure contains nitric nitrogen. 



* 106. Test for Potash. — Heat a little of the manure 

 on platinum foil in the Bunsen flame until all the carbo- 

 naceous matter is burned off. Remove the ash which is left to 

 a watch-glass and moisten it with hydrochloric acid. Test the 

 substance in the flame on a loop of platinum wire, viewing 

 the colour through an indigo-prism or a piece of cobalt-blue 

 glass. Should the flame, when viewed thus, appear crimson, 

 the manure contains potash. The most usual forms in 

 which potash is added to mixed manures are sulphate of 

 potash, muriate of potash, and kainit, which is a double 

 sulphate of potash and magnesia. 



