i8o Sanitary Studies of Baking Powders 



sol. would embrace all the analytical difficulties usually encountered 

 in determining aluminum in the presence of large amounts of or- 

 ganic matter (after incineration). The results of these analyses are 

 recorded in Table 4. 



9. ESTIMATION OF ALUMINUM IN THE PRESENCE OF ORGANIC 

 MATTER BY EACH OF THE THREE METHODS NOTED IN SUB-SECTIONS 

 6, 7 AND 8. 



Oxidation of the organic matter: 25 gm. of hashed lean beef and 

 30 cc. of H0SO4 were placed into each of 4 Kjeldahl flasks marked 

 A, B, C, and D. To each of flasks A and B, 30 cc. of the Standard 

 alum sol., 60 cc. of the Standard iron sol., and 10 cc. of conc. HNO3 

 were added. To each of flasks C and D, 60 cc. of the Standard 

 alum sol., 120 cc. of the Standard iron sol., and 10 cc. of conc. HNO3 

 were added. The mixtures were digested until the sol. became color- 

 less. When necessary, small quantities of ammonium nitrate were 

 added f rom time to time to facilitate the oxidation process. 



On cooling, 20 cc. of conc. HCl and 100 cc. of water were intro- 

 duced, and this mixture was heated to boiling and filtered into a 300 

 cc. flask. After washing the residue with water, it was washed into a 

 beaker with water and 10 cc. of conc. HCl were added. This was 

 boiled, diluted with water and filtered into the flask containing the first 

 filtrate. If any residue remained, which rarely occurred, it was treated 

 in the same manner and the filtrate was again added to the flask. On 

 cooling to room temp., each flask was made up to vol. Aliquot por- 

 tions of these sol. were used for estimating the iron and aluminum 

 Contents. Since the Volumetrie flasks contained 300 cc, in flasks A 

 and B 50 cc. portions were equivalent to 5 cc. of the Standard alum sol., 

 and IG cc, of the Standard iron sol. In flasks C and D, 50 cc. portions 

 were equivalent to 10 cc. of the alum sol. and 20 cc. of the iron sol. 



The iron content was estimated on samples from each flask and 

 the results, which were remarkably concordant, were but a fraction 

 of a milligram higher than the average of the results obtained on 

 equivalent portions of the original Standard ferric chlorid sol. This 

 slight increase may be attributed to the iron content of the beef. 

 There was no increase in aluminum. The results obtained by all 

 three methods are recorded in Table 5. 



