WAGNER'S METHOD FOR PHOSPHORIC ACID 201 



below. After filling to the mark with water it is shaken for half 

 an hour and filtered. To 50 cubic centimeters of the filtrate are 

 added 100 cubic centimeters of molybdic solution and the whole 

 heated to 80. After cooling, the precipitate is filtered and the 

 phosphoric acid estimated in the usual way. 



The acid ammonium citrate solution used is made as follows: 

 Dissolve 1 60 grams of citric acid with enough ammonia to repre- 

 sent about 28 grams of nitrogen and make up with water to one 

 liter. 



The molybdic solution is made by dissolving 125 grams of 

 molybdic acid in a slight excess of 2.5 per cent, of ammonia, 

 adding 400 grams of ammonium nitrate, diluting to one liter and 

 pouring the solution into one liter of nitric acid having a specific 

 gravity of 1.19. After allowing to stand at room temperature 

 for one day the mixture is filtered and is then ready for use. 



175. Wagner's Method for Phosphoric Acid. The directions giv- 

 en by Wagner for determining the phosphoric acid in slags and 

 raw phosphates soluble in citrate solutions are the following: 51 

 Five grams of the material as it is sent into commerce, without 

 grinding or sifting, are placed in a half-liter flask, covered with 

 nearly a quarter liter of water, and then 200 cubic centimeters of 

 citrate solution added, prepared as described below. The flask 

 is filled to the mark with water. The flasks, which are of the 

 shape shown in the figure, are closed with rubber stoppers, and 

 without delay placed for half an hour in a rotating apparatus, 

 ( Fig. 1 1 ) , which is turned on its axis from 30 to 40 times a min- 

 ute. If a shaking apparatus be used instead of the one men- 

 tioned, 200 cubic centimeters of the citrate solution should be 

 placed in a half-liter flask, filled to the mark with water, and the 

 contents poured into a liter flask containing the phosphate. This 

 flask should be placed in a nearly horizontal position in the ap- 

 paratus and the agitation be continued for half an hour. On 

 removal from the apparatus the mixture is filtered and 50 cubic 

 centimeters thereof treated with double that quantity of molybdic 

 solution at 80 and the precipitate separated after cooling. The 

 precipitate is carefully washed with one per cent, nitric acid mix- 



" Chemiker-Zeitung, 1894, 18 : 1933. 



