22 PHOSPHATE OF SODA AND AMMONIA. 



adulterated with Glauber's salt will give a proportion- 

 ally smaller quantity of the phosphate. Since 45.12 

 parts of 2 MgO, PO 5 correspond to 100 parts of crys- 

 tallized sulphate of magnesia, a specimen of the latter 

 which yields, for example, only 40 parts of 2 MgO, 

 PO 5 would contain only 88.3 per cent, of true Epsom- 

 salt, and 11.7 per cent, of Glauber's-salt. 



In order to test Epsom-salt for Glauber's-salt, the 

 specimen is mixed with powdered charcoal, dried, and 

 heated in a crucible to bright redness. If sulphate of 

 soda be present, water will dissolve out of the cold 

 mass sulphide of sodium, which, when treated with 

 hydrochloric acid, is converted into chloride of sodium, 

 with evolution of sulphuretted hydrogen. 



Or the solution of the salt to be tested may be pre- 

 cipitated by hot saturated baryta-water, filtered, the 

 excess of baryta precipitated from the solution by a 

 mixture of ammonia and carbonate of ammonia, and 

 the filtrate evaporated, when, if any Glauber's-salt have 

 been present, carbonate of soda will be left. 



9. PHOSPHATE OF SODA AND AMMONIA* 

 NaO, NH 4 0, HO, P0 5 +8 HO. 



A weighed quantity of the salt is gradually and 

 cautiously heated in a platinum crucible, the heat being 

 finally raised to ignition, and continued till the salt is 

 in a state of tranquil fusion. The ammonia and water 

 are thus expelled, their joint amount being indicated 

 by the loss of weight. The fused residue is NaO, P0 5 . 



* Six parts of crystallized phosphate of soda are dissolved, with 

 the aid of heat, in 2 parts of water, and in this solution 2 parts of 

 chloride of ammonium are dissolved. Tlie filtered liquid deposits 

 crystals of the new salt which are purified by solution in hot atu- 

 mouiacal water and recrystallization. 



