IRON AND ALUMINA IN PHOSPHATES 237 



driven off. This treatment is necessary to prevent the iron phos- 

 phate precipitate from being contaminated with magnesia. The 

 precipitate is collected on a filter, washed four times with hot 

 water, or water containing neutral ammonium nitrate, dried, 

 ignited, and weighed. One-half of the weight of the precipitate 

 represents the weight of the ferric and aluminic oxids. The 

 magnesia is thrown out of the filtrate by saturation with ammonia 

 and allowing to stand 12 hours. The phosphoric acid, alkalies 

 and sulfuric acid are determined in the original sample by the 

 usual methods. Jones' variation of the E. Glaser method has 

 been generally approved by experience and is to be recommended 

 in general in place of the original process. 94 



209. Estimation of Iron and Alumina in Phosphates by Crispo's 

 Method. The phosphate of ferric iron is subject to a .slight de- 

 composition in presence of both hot and cold water with a ten- 

 dency to the production of basic compounds. It is soluble to a 

 slight extent in hot and cold acetic acid, almost insoluble in am- 

 monium acetate, and quite insoluble in ammonium chlorid and 

 nitrate. Aluminum phosphate is likewise soluble, to a slight de- 

 gree, in acetic acid and ammonium acetate, and insoluble in am- 

 monium chlorid and nitrate. The method of Crispo, as practiced 

 in the laboratory at Antwerp, for the separation of iron and alu- 

 mina in phosphates is based on the above properties. 95 Five grams 

 of the mineral phosphate are dissolved in 500 cubic centimeters 

 of aqua regia, containing 40 cubic centimeters of hydrochloric 

 acid of i.io, and 10 of nitric acid of 1.20 specific gravity. To 50 

 cubic centimeters of the filtered solution are added two of 

 ammonia (0.96) and 50 of a half-saturated solution of ammo- 

 nium chlorid, and the whole boiled. The liquid should remain 

 clear, but if it becomes cloudy add a little dilute nitric acid, drop 

 by drop, until the turbidity is removed, and then 10 cubic cen- 

 timeters of a saturated solution of ammonium acetate, boil for 

 three minutes, cool, and filter. The precipitate is washed twice 

 with a 10 per cent, solution of ammonium chlorid and redis- 

 solved with two cubic centimeters of nitric acid, and the filter 



94 von Griiber, Zeitschrift fur analytische Chemie, 1891, 30 : 206. 



95 First International Congress of Applied Chemistry, Brussels, 1894, 

 Proceedings : 20. 



