METHOD OF LASNE 249 



Third Phosphate in products such as farm-yard manure, poud- 

 rette, guano, etc. 



Fourth Phosphates which have been treated by chemical pro- 

 cesses producing superphosphates whether from bone or mineral 

 phosphates, precipitated phosphates, ammoniaco-magnesium phos- 

 phates, etc. 



Fifth Phosphates which are produced in metallurgical opera- 

 tions, such as basic slag, etc. 



The methods employed for these various processes are not es- 

 sentially different from those which are already described. There 

 are certain slight variations in the methods of preparation which 

 are of interest but do not introduce any new principles or methods 

 of procedure. 



219. Method of Lasne. 8 With ordinary phosphates, contain- 

 ing as much as three per cent, of alumina a convenient quantity 

 to use is two grams. If the phosphate be poor in alumina, a 

 larger quantity may be employed. The phosphate in a fine powder 

 is dissolved in hydrochloric acid with or without the addition of 

 nitric acid, as may be desired. The solution is evaporated to 

 dryness, moistened several times with hydrochloric acid and 

 again dried to render the silica totally insoluble. The soluble 

 parts of the residue are taken up in dilute hydrochloric acid 

 (one part strong acid to 20 of water) so as not to have more than 

 1.5 grams of HC1 to each gram of phosphate. The solution may 

 be either filtered and washed or made up to a known volume, fil- 

 tered through a dry filter and an aliquot part of the filtrate em- 

 ployed for the subsequent analysis. 



A convenient quantity of the filtrate to employ is one which cor- 

 responds to 1.25 grams of the original phosphate in case two 

 grams have been taken. 



Meanwhile, there should be prepared a solution of five grams 

 of caustic soda free of alumina and silica. This is dissolved in a 

 nickel dish with about 10 cubic centimeters of water. The quan- 

 tity of soda to be employed is to be calculated as follows : Two 

 grams per gram of the phosphate and one gram for each 100 

 cubic centimeters of the final volume employed. There is added 

 8 Bulletin de la Societ^ chimique de Paris, 1896, [3], 15:6, 118, 146, 

 237- 



