Superphosphate 3 



(a) Weight of Ca3P208 in 200 grams rock phos- 



phate, grams. 



(b) Weight of H2SO4 required for 200 grams rock 



phosphate, grams. 



(c) Volum of chamber acid required for 200 grams 



rock phosphate, cc. 



(d) Volum to which the (c) cc. of chamber acid must 



be diluted, cc. 



- Procedure. — Measure out the volum (c) 

 of chamber acid and pour it into (d-c) cubic 

 centimeters of water in a porcelain dish. 

 Weigh out 200 grams of the rock phosphate 

 and stir it slowly into the acid. Let the 

 mixture stay in the evaporating dish until 

 the next exercise. The hydrofluoric acid 

 fumes that arise are to be avoided. 



Notebook; Test for Soluble Phosphates. 



— Shake a little of the superphosphate with 

 water, filter the solution, add to the filtrate a 

 solution of ammonium molybdate and warm 

 the liquid gently in a test tub^. If the yellow 

 precipitate of ammonium phosphomolybdate 

 does not form after a few seconds its ap- 

 pearance may be hast end by adding a gram 

 or two of solid ammonium nitrate. The 

 addition of ammonium hydroxid followd 

 by nitric acid will accomplish the same result 

 including the heating; when this is done the 

 solution must be left acidic with nitric acid. 



If some of the natural rock phosphate is 



