Clarence A. Smith and Philip B. Hawk 185 



exceedingly long and tedious. After the oxidation was completed 

 each portion was transferred to a 500 cc. vol. flask and diluted to 

 the mark with dist. water. Aluminium was then determined, by each 

 method, in 200 cc. portions of these sol. A 200 cc. portion of the 

 sol. obtained f rom the blood to which alum sol. had been added, con- 

 tained the equivalent of 8 mg. of AUOg, while a 200 cc. portion of 

 the other sol. contained no added alum. 



The Standard alum sol. was used directly for the determination 

 of aluminium by each method, and was also mixed with ferric 

 chlorid sol. in different amounts and analyzed by each method. 



The method proposed by SteeP and modified by Kahn^ depends 

 upon the precipitation and weighing of the iron and aluminium as the 

 phosphate. Iron is determined in the original sol. by the Zimmerman- 

 Reinhardt permanganate titration method, which is described by Mixer 

 and DuBois,'^ and ferric phosphate is calculated from this value. The 

 weight of ferric phosphate is subtracted from the weight of pre- 

 cipitated ferric and aluminium phosphates to obtain the weight of 

 aluminium phosphate. Each cc. of the permanganate sol. used was 

 equivalent to 7.15 mg. of ferric phosphate. 



The precipitation is carried out in the following manner: Mix the 

 acid sol. in which the aluminium is to be determined, after the removal 

 of silica, with sodium phosphate sol. in excess of the amount needed 

 to form normal aluminium phosphate with the aluminium present. 

 Add sufficient ammonium hydroxid sol. to effect the complete precipita- 

 tion of the aluminium phosphate after thorough stirring, then add 

 hydrochloric acid, drop by drop, until the precipitate completely dis- 

 solves. Heat the liquid to about 50° C. and mix with it, at that temp., 

 a considerable excess of ammonium acetate sol. (50 percent) and also 

 4 cc. of 80 percent acetic acid sol. As soon as the precipitate of 

 aluminium phosphate (mixed with iron phosphate) has sedimented, 

 collect it on an ashless filter, wash with hot water, ignite and weigh the 

 residue of AIPO^ which is mixed with FeP04. 



The method used by Schmidt and Hoagland^ for the determination 

 of aluminium in feces depends upon the precipitation and weighing of 

 aluminium as the phosphate, the iron present being kept in sol. in the 



^ Steel, M. : Loc. cit. 

 ^ Kahn, M. : Loc. cit. 



7 Mixer, C. T., and DuBois, H. W. : Jour. Amer. Chem. Soc, 1895, xvii, p. 405. 



8 Schmidt and Hoagland : Loc. cit. 



