802 EXPERIMENT STATION EECOBD. [Vol. 35 



The action of nitric acid on aluminum, R. Sbxigman and P. Williams 

 (Jour. Soc. Chem. Indus., 35 (1916), No. 12, pp. 665-672, figs. S).— From a study 

 of the action of nitric acid on aluminum the most important condition found 

 to affect the rate of dissolution of the metal was the temperature of the acid. 

 An increase of 10° C. over a considerable range of temperature was found 

 sufficient to increase the rate of dissolution 100 per cent. 



Next to temperature the concentration played the most prominent part in 

 determining the rate of solution. Mixtures containing between 20 and 40 per 

 cent by volume of nitric acid (specific gravity 1.42) were found to be the most 

 active, while some samples containing as high as 94.7 per cent nitric acid were 

 found to be almost without effect on the metal. A sample of aluminum sus- 

 pended in such acid for 71 days lost only 0.0004 gm., equivalent to a rate of 

 dissolution of 0.015 mg. per 100 sq. cm. per 24 hours. 



Contrary t<» the statements of earlier investigators, the presence of 0.05 per 

 cent chlorin in the acid was found not t© affect the rate of solution. The same 

 condition was found to prevail in the case of iodin up to concentrations of 0.01 

 per cent. Traces of sulphm-ic acid and the presence of the lower oxids of 

 nitrogen, however, increased the rate of solution markedly. The action of the 

 acid on the metal could be considerably reduced by freeing it from such oxids. 



The effect of the physical state of the metal was considerable, the amoi*phous 

 form being attacked much more readily than the crystalline. The composition 

 of the metal was found to be of lesser importance, the pure metal, however, 

 being generally found to be the most resistant to the attack of the acid. No 

 local action or " pitting " was observed. 



The apparatus and experimental methods used in the study are described in 

 detail. 



Sanitary studies of baking powders (Biochem. Bui., 5 (1916), No. 20-21, pp. 

 158-202). — The following studies on suitable analytical methods for the deter- 

 mination of small amounts of aluminum are reported. 



II. A comparison of the method proposed by the Association of Official Agri- 

 cultural Chemists as modified hy Steel with that described by Schmidt and 

 Hoagland for the determination of aluminum in organic material, P. E. Howe 

 (pp. 158-164). — From experimental data reported it is concluded that, when 

 compared to the results obtained vnth the procedure recommended by Schmidt 

 and Hoagland," for small amounts of aluminum in the presence of iron and 

 phosphates the method proposed by the Association of Official Agricultural 

 Chemists as modified by Steel in an article previously noted (E. S. R., 25, p. 

 573) yields values which are essentially the same in the case of pure aluminum 

 salts, but slightly lower when applied to blood to which aluminum sulphate 

 has been added. 



III. A study of the methods for the quantitative determination of aluminum 

 in blood, L. J. Curtman and P. Gross (pp. 165-172). — The authors have found 

 the method of Steel to be unreliable, due to the instability of ferric phosphate. 

 For the determination of small quantities of the metal in the presence of large 

 amounts of iron the method is unsatisfactory. The procedure of Schmidt and 

 Hoagland yielded accurate results both in pure solution of aluminum salts and 

 in blood. 



It is indicated that the procedure of Schmidt and Hoagland is superior to 

 that of Steel from the standpoint of technique for the following reasons: "(1) 

 A direct gravimetric determination of aluminum is effected. No volumetric 

 solution or operations are required and the aluminum is not found by difference 

 (thus taking the sum of the errors). (2) The determination is made on the 



"Jour. Biol. Chem., 11 (1912), No. 4, pp. 387-391. 



