132 SPECIAL METHODS OF ANALYSIS. 



moistened lead-paper that is lield in the mouth of 

 the tube. {Hydrosulphurlc.) Sulpiiue. - - . 9 

 9. The first sohition, or F 2, after acidification with 

 hydrochloric acid, if not already acid, gives a white, 

 finely pulverulent precipitate with baric chloride. 



Sulphuric. - -10 



Sulphuric acid may be found also in the insoluble 

 substance in the course of the examination for 

 bases. 



10. If a very small quantity of the solution of the sub- 

 stance is added to ammonic molybdate, a pale yel- 

 low precipitate is formed, at once, or after some time, 

 a part of which adheres strongly to the sides of 

 the tube ; the precipitate is soluble in ammonia. 

 Phosphokic. 11 



11. To a portion of the hot solution, containing a 

 slight excess of acid, add about twice its volume 

 of alcohol, and then dilute sulphuric acid or am- 

 nionic sulphate, and filter if any precipitate is 

 formed, heat the filtrate until the alcohol is ex- 

 pelled, add ammonia in shght excess, and then 

 acetic acid until the ammonia is more than neutral- 

 ized, and finally calcic sulphate. A fine white pre- 

 cipitate appears, at once, or after some time. 

 Oxalic. 12 



12. To a smnll portion of the dilute nitric acid solu- 

 tion of the substance, or of the aqueous solution 

 acidified with nitric acid, add argentic nitrate. 



a. No precipitate is formed. (Traces of cyano- 

 gen or iodine may perhaps be found by applying 

 the tests in 12 5, and 13.) 17 



b. A precipitate is formed. 



Treat a small portion of the original substance 

 with a little dilute sulphuric acid, in a watch-glass, 

 and quickly invert another watch-glass, with a 



