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])ETERMIXATIOX OF PHOSPHORIC OXIDE. 



The Determixatiox of Small Amounts. 



Tlie process is particularly useful for determining- very 

 small quantities of phosphoric oxide. For this purpose it 

 compares favourably with colorimetric processes, in that the 

 phosphate solution may contain substances which interfere 

 Avith the coloiir comparison, and the standard solution need 

 not be adjusted to the composition of the solution, to be tested. 

 The full method may be carried out, or, if the volume of the 

 phosphate solution be small, the volumes of tiie reag-ents 

 may be reduced proportionately. In the latter case "we have 

 found that the precipitate is usually obtained in a finely 

 divided state and is somewhat difficult to filter and wash. 

 One-hundredth normal alkali and acid imxj be used ; the end 

 point is quite sharp. The following- results were obtained 

 on a solution of dicalcium ])hosphate in nitric acid ; they 

 illustrate the possibilities of the method when applied to the 

 determination of small (luantities : — 



Eegular Method: Fixal Volume 100 c.c* 



Results by B. .J. Sniit, Assistant Chemist. 



