SANITARY STUDIES OF BAKING POWDERS 



2. A comparison of the method proposed by the Association 



of Official Agricultural Chemists as modified by Steel, 



with that described by Schmidt and Hoagland, for the 



determination o£ aluminum in organic material. 



PAUL E. HOWE 



(Biochemical Laboratory of Columhia University, at the College of Physicians 



and Surgeons, New York) 



(Received for publication, July lo, 1915) 



Introduction. The method used by SteeP and Kahn,^ for the 

 determination of aluminum in organic material, was compared with 

 that described by Schmidt and Hoagland^ for the same purpose. 

 Steel, after examining various methods for the determination of 

 aluminum in the presence of iron and phosphates, selected the one 

 proposed by the Assoc. of Official Agric. Chem.^ as the most accurate 

 He modified this in that the iron was determined in an aliquot por- 

 tion of the sol. to be analyzed, instead of in the combined, ignited, 

 precipitate of aluminum and iron phosphates. Schmidt and Hoag- 

 land studied the conditions under which the Peters method for the 

 precipitation of aluminum in the presence of iron could be used in 

 accurate work. 



I. The method used by Steel, as described by Kahn, was as 

 f ollows : Prelhninary oxidation of organic material: " The weighed 

 tissue was placed in a Kjeldahl flask and conc. nitric acid sol. added 

 to it. The flask was heated slowly at first and then more vigorously 

 until the sol. became clear, when a moderate excess of nitric acid sol. 

 was added and the liquid boiled down to a small volume. The fluid 



1 Steel: Amer. Jour. Physiol., 191 1, xxviii, p. 94. 



2 Kahn: Biochem. Bull., 1911, i, p. 235. 



' Schmidt and Hoagland : Jour. Biol. Chem., 1912, xi, p. 387. 

 * Bull. 107, U. S. Dep't of Agric, 1907, p. 177. 



158 



