A SIMPLE, EFFICIENT, AND ECONOMIC FILTER 



Its application to the filtration of the yellow precipitate in 

 phosphoric-acid estimations^ 



S. L. JODIDI AND E. H. KELLOGG 



{Office of Plant Physiological and Fermentation Investigations, Bureau of Plant 

 Industry, U. S. Department of Agriculture, Washington, D. C.) 



(Received for publication, July 21, 1915). 



Introduction. General considerations in connection with our 

 work on the chestnut-blight disease led us to make phosphoric-acid 

 determinations for the various barks, healthy and infected, in ac- 

 cordance with Neumann's^ method. It was soon found by the 

 senior author^ that while Neumann's method is rehable and con- 

 venient, the calculation- facto r, 0.554, is too low under certain con- 

 ditions, a finding- in füll agreement with the work of Heubner.^ 

 Further investigation^ revealed the fact that the amount of water 

 used for washing the yellow precipitate has a certain influence on 

 the calculation-factor. While the work according to Neumann's 

 method was going on, we were impressed by the fact that the filtra- 

 tion of the ammonium-phosphomolybdate precipitate through a 

 folded filter, as recommended by Neumann, is a tedious and time- 

 consuming Operation. A search for a better filtering medium finally 

 led US to the paper-pulp filter. 



New mechanical devices, like new chemical methods, are of 

 more or less importance to science, which is true, e. g., of the well- 

 known Gooch crucible (as well as of the Munroe^ crucible) , the intro- 



1 Presented at the Second Pan-American Scientific Congress, Washington, 

 D. C, January 4, 1915, and published by permission of the Secretary of Agri- 

 culture. 



2 Neumann: Z. physiol. Chem. 37, 129 (1902-03) ; 43, 35 (i904-0S)- 



3 Jodidi : Journ. Amer. Chem. Soc., 37, 1708 (i9i5)- 

 ^Heubner: Biochem. Z., 64, 393 (1914). 



5 Jodidi and Kellogg: Jour. Franklin Institute, 180, 349 (i9i5)- 

 «Munroe: Chem. News, 58, loi (1888) ; Jour. Analyt. Chem., 2, 241 (1888). 



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