ipii] Max Kahn 237 



distribution of all the ingredients. The dough was well kneaded 

 and baked in tin pans very thoroughly (more so than the house- 

 wife's ordinary biscuits). The biscuits were very crisp and toasty 

 when removed f rom the oven. 



I analyzed several 20 gram portions (A — D) of the baked bis- 

 cuit from several days' baking, with the following results for alu- 

 minium in terms of AI2O3 : 



A — 3.36 mg. ; B — 3.61 mg. ; C — 2.28 mg, ; D — 4.16 mg. 



Method for the quantitative determination of aluminium. 



The results of Dr. Steel's work in this laboratory, and my own 

 experience with the process, led me to adopt the following method 

 of analysis, as recommended by the Association of Official Agricul- 

 tural Chemists.^ 



Obtain an aliquot portion of the available acid Solution (after 

 oxidation, vide infra) and remove any contained silica. Mix the 

 liquid with sodium phosphate Solution in excess of what is required 

 to form normal aluminium phosphate. Add sufficient ammonium 

 hydroxide Solution to effect complete precipitation of the aluminium 

 phosphate after thorough stirring. Thenadd hydrochloric acid Solu- 

 tion, drop by drop, until the precipitate completely dissolves. Heat 

 the liquid to about 50° C. and mix with it, at that temperature, a 

 considerable excess of 50 per cent. ammonium acetate Solution and 

 also 4 c.c. of 80 per cent. acetic acid Solution. As soon as the pre- 

 cipitate of aluminium phosphate (mixed with iron phosphate) has 

 sedimented, collect it on an ashless filter, wash it with hot water, 

 ignite it and then weigh the residue. 



In an aliquot portion of the original acid liquid determlne the 

 amount of iron by the Zimmerman-Reinhardt method."^ The calcu- 

 lated amount of FeP04 is then subtracted from the weight of the 

 mixed AIPO4 and FeP04. 



Many determinations were made by this method in mixtures of 

 pure Standard Solutions of ferric chlorid and aluminium sulfate, and 

 perfectly accurate results were obtained. 



Preliminary oxidation of the analyzed tissues. Every tis- 



•U. S. Dept. of Agriculture, Bureau of Chemistry, Bulletin 107, 1908. 

 ^ Mixer and Dubois : Journal of the American Chemical Society, 1895, xvii, 

 P- 405. 



