74 PROCEEDINGS OF THE AMERICAN ACADEMY 



does not exceed (let us say) 0.05 gr., but for amounts larger than this 

 the method of double precipitation recommended for the phosphotung- 

 states is more accurate. 



As to the time which should be allowed to pass between precipitat- 

 ing and filtering, my experiments support those of Abesser, Jani, and 

 Marcker * in pointing to the conclusion that a precipitate may be 

 filtered with safety as soon as it has completely subsided, or, after ten 

 or fifteen minutes. 



The use, for the filtration and ignition of the precipitate, of the 

 method which I have employed in the experiments described above 

 greatly expedites the analysis. Thus, with two perforated crucibles at 

 my disposal, I have completed within four and one-half hours from the 

 measuring out of the first solution seven determinations of the phos- 

 phoric oxide of an alkaline phosphate, — the ignition of each pre- 

 cipitate requiring less than five minutes. 



* Zeitschrift fur Anal. Chem. XII. 250. 



