SOLUTION OF REVERTED PHOSPHATES 149 



and is transferred to a precipitating glass of about 300 cubic 

 centimeters capacity. 



137. Solution of the Reverted Phosphates by Ammonium Citrate. 

 The filter from the above process is detached from the funnel 

 and is introduced into a flask marked at 150 cubic centimeters 

 together with 60 cubic centimeters of alkaline ammonium citrate 

 prepared in the following manner : 

 Pure citric acid, 400 grams. 

 Ammonia of 22, 500 cubic centimeters. 



The ammonia is poured upon the crystals of citric acid in a 

 large dish. The mass becomes heated, and the solution takes place 

 rapidly. When it is complete and the solution is cold, it is poured 

 into a flask of one liter capacity, and the flask is filled up to the 

 mark with strong ammonia. It is preserved for use in a well 

 stoppered bottle. The solution must be strongly alkaline. 



The flask in which the filter paper is introduced, together with 

 the ammonium citrate, is stoppered and shaken violently in order 

 to disintegrate the filter paper and get the reverted phosphates 

 in suspension. There are added then about 60 cubic centi- 

 meters of distilled water, and the flask is shaken and left for 

 12 hours at least, or at most for 24 hours. The volume is 

 made up to 150 cubic centimeters with distilled water, and after 

 mixture the solution is filtered. 



There are thus obtained two solutions, one with water and one 

 with the alkaline ammonium citrate, which can be precipitated 

 together or separately, according to circumstances. The usual 

 process is to combine equal volumes of 25, 50, or 100 cubic 

 centimeters, representing one-quarter, one-half or one gram of 

 the material according to its presumed richness, in a precipitat- 

 ing flask to which are added from 10 to 20 cubic centimeters of 

 the solution of magnesia made up as follows : 



Magnesium carbonate, 50 grams. 

 Ammonium chlorid, 100 grams. 

 Water, 500 cubic centimeters. 



Hydrochloric acid, 120 cubic centimeters. 



After complete solution of the solid matters in the above, add 



