PHOSPHATE OF MAGNESIA AND AMMONIA. 23 



The determination of the ammonia is effected as in 

 No. 5, with another portion of the salt. 



In order to determine the phosphoric acicl, the salt 

 is dissolved in water and mixed with chloride of am- 

 monium, ammonia and sulphate of magnesia, the pre- 

 cipitatate being treated as in No. 6. The ignited 

 2MgO, P0 5 contains 63.55 per cent, of phosphoric acid. 



For the direct determination of the soda, a weighed 

 quantity of the salt is dissolved in water, and the phos- 

 phoric acid precipitated by acetate of lead. From the 

 filtered liquid, the excess of oxide of lead is removed 

 by a mixture of ammonia and carbonate of ammonia, 

 the solution heated to ebullition, filtered, evaporated 

 to dryness and the residual acetate ignited, with access 

 of air, until the carbonate of soda is colorless. 



Asa control for the determination of the phosphoric 

 acid, the phosphate of lead may be decomposed by 

 heating with dilute sulphuric acid, and the phosphoric 

 acid precipitated from the filtrate by sulphate of mag- 

 nesia, as directed above. 



10. PHOSPHATE OF MAGNESIA AND AMMONIA* 

 2 MgO, NH 4 0, P0 5 + 12 HO. 



By ignition the salt is converted into 2 MgO, P0 5 . 



The ammonia is determined by dissolving the salt 

 in the smallest possible quantity of hydrochloric acid, 

 mixing the solution with bichloride of platinum and 

 alcohol, and treating the ammonio-chloride of platinum, 

 as in No. 5. 



In order to separate and determine the phosphoric 



* Prepared by precipitating a solution of sulphate of magnesia 

 to which much chloride of ammonium has been added, by phos- 

 phate of soda, and washing the precipitate with dilute ammonia. 



