178 Sanitary Studie s of Baking Powders 



C. — The use of methyl orange as the indicator to control the 

 acidity on adding the ammonium acetate. 



D. — Redissolving the phosphate precipitate in dilute HCl sol. 

 and performing a second precipitation with ammonium 

 acetate. 



E. — The use of a " Meker " burner instead of a blast lamp. 



F. — Using the Jones and Jeffrey modification of the Zimmer- 

 man-Rheinhardt method (14) for the estimation of iron 

 instead of the Mixer and DuBois (15) modification of 

 the same method used by Steel (16). 



TABLE 3 



Data pertaining to the estimation of iron and alutninum by the method proposed 

 by the Government Research Committee 



8. Estimation of aluminum in the Standard alum sol. by 

 THE Schmidt and Hoagland method (17). In aqueous sol. 

 this method is comparatively simple. The technique is essentially as 

 f ollows : 



To the acid sol. one adds 0.5 gm. of ammonium phosphate for each 

 100 mg. of AIPO4 known to be present. The sol. is then heated and, 

 while hot, 5 gm. of ammonium thiosulphate (in sol.) are introduced; 

 the sol. is allowed to stand awhile, then 6 to 8 gm. of ammonium acetate 

 (in sol.) and 4 cc. of strong acetic acid are added. The mixture is 



