i84 Sanitary Studies of Baking Powders 



tained 0.002 gm. of AI2O3 per cc, and was added in known amounts 

 to the blood and gastric juice to be analyzed for aluminium. It was 

 used also for analysis directly and after being mixed with ferric 

 chlorid sol. 



Preliminary treatment of gastric juice. Clear gastric juice 

 was obtained by mixing and filtering several samples of juice ob- 

 tained from different subjects after ingestion of Ewald or other 

 test meals. These subjects were used in experiments not con- 

 nected with this investigation, and in no case did the meal ingested 

 contain any bread made with alum baking powder. Known amounts 

 of the Standard alum sol. were added to this clear juice, and the 

 juice was then analyzed, either directly or after ashing, in the 

 f ollowing manner : 



To 50 cc. portions of this clear gastric juice, 10 cc. portions of 

 the Standard alum sol. (equivalent to 20 mg. of AI0O3) were added, 

 and the aluminium determined in the resulting mixtures by each 

 method. To another portion of the clear gastric juice (approxi- 

 mately 200 cc), 25 cc. of the Standard alum sol. (containing the 

 equivalent of 50 mg. of AI2O3) were added, and the mixture evapo- 

 rated to dryness in a silica dish on a water-bath. When nearly 

 dry, the residue was ashed over a free flame with the aid of conc. 

 nitric acid. The ash was taken up with hydrochloric acid, dehy- 

 drated to remove silica, again taken up with a little hydrochloric acid 

 and water, filtered into a 250 cc. vol. flask, and diluted to the mark 

 with dist. water. Fifty cc. portions of this sol. (containing the 

 equivalent of 10 mg. of added AI2O3) were then analyzed for alu- 

 minium by each method. 



Preliminary treatment of the beef blood. Twenty cc. of the 

 Standard alum sol. (equivalent to 40 mg. of AI2O3) were added to 

 approximately 500 cc. of oxalated'* beef blood. Another portion of 

 approximately 500 cc. was used as a check and received no addition 

 of alum sol. The two portions of blood were then placed in 2-liter 

 round-bottomed Jena flasks, and oxidized by heating with conc. 

 nitric and sulfuric acids, using small amounts of potassium per- 

 manganate to complete the oxidation. The process of oxidation was 



* Some clotting occurred due to faulty shaking during the collection of the 

 blood. 



