AGRICULTURAL CHEMISTRY AGROTECHNY. 707 



Determining- barium sulphate in the presence of interfering substances, 

 M. J. Van't Kruijs {Ztschr. Aualyt. Clicin., J,i) (1010), A>j. 7, pp. 3!J3-.'il9). — 

 Previously noted from another source (E. S. R., 22, p. 707). 



Volumetric method for barium salts, E. Selvatici (Bui. Assoc. Chini. Sucr. 

 et DisliU.. 27 (I'JIO), \o. 9, pp. Sdi-Sli'i ; ah-s. in Chetn. Ahs., J, (1910), No. 12, 

 p. l.')9l). — This is :i modiflcatiou of Gurelli and llavenna's method and is as 

 follows: 



Fifiy cc. of a boiling solution of the sample to be examined is placed in a 50 

 cc. flask, cooled, filled up to the mark, and the suspended matter allowed to sub- 

 side. Twenty cc. of the solution is then taken in a 100 cc. fliisk, a few drops of 

 acetic acid added, and GO cc. of bichromate solution (4.6G gm. of pure potassium 

 bichromate dissolved in w^ater and made up to the 1,000 cc. mark) run in, the 

 flask filled up to the mark, shaken, and the contents filtered. To 50 cc. of the 

 nitrate is added 10 cc. of the potassium iodid solution (KI in HCl), and the 

 iodin set free with thiosuli)hate solution (23.567 gm. sodium thiosulphate dis- 

 solved in water and filled up to the 1,000 cc. mark), estimated, using starch 

 paste as the indicator. As the bichromate and thiosulphate solutions balance, 

 the difference between them represents the amount of potassium bichromate 

 solution combined with the Ba(OH)2+SH20. 



[Extraction of plant food constituents], J. M. Bell (Jour. Amcr. Chcra. Soc, 

 32 (1910). Xo. 7, pp. 879-SSJi).—A discussion of the work of ^^litscherlich and 

 others (E. S. R., 23, p. 302), with particular reference to the extraction of 

 plant food constituents from the phosphates of calcium and a loam soil, and 

 the usual equation expressing the rate of solution, namely, (ly/dt=k(A — y), in 

 which it is claimed that Mitscherlich misinterpreted the meaning of A. The 

 author recalculated Mitscherlich's figures and concludes that " notwithstanding 

 the conditions militating. against the use of the ordinary equation for rate of 

 solution, viz, the variable extent of surface and the fact that the phenomenon 

 observed is not one of solution only but also of hydrolysis, this equation de- 

 scribes the data at least as well as the empirical equation proposed by Mitscher- 

 lich, Kunze, Celichowski, and Merres. The usual equation for rate of solution 

 also describes verj- well the extraction of lime from a loam soil by carbonated 

 water." 



Analysis of proteins, A. Etard and A. Vila (Compt. Rend. Acad. l:^ci. [Paris], 

 loO (1910), Xo. 25, pp. 1109-1111; ahs. in Analyst, 35 (1910), Xo. J,13, p. 366).— 

 On the basis of the use of pure methyl alcohol for separating and drying tli(> 

 mixture of amino acids formed by hydrolysis, and the use of barium hydrate 

 in a solution of methyl alcohol as a precipitant of the substances formed ," the 

 authors now describe a number of reactions by which these products can be 

 further separated into groups. 



By adding sulphuric acid and methyl alcohol to the filtrate obtained from 

 the barium precipitate certain basic substances are separated which can be 

 removetl by filtration. This filtrate is then treated with a solution of hydro- 

 ferrocyanic acid (prepared by treating i)otassium ferrocyanid with an equal 

 quantity of hydrochloric acid and precii»itating th(* hydroferrocyanic acid with 

 ether) in methyl alcohol, when another group of basic substances is jirecipi- 

 tated. The amino acids remaining in the final filtrate are obtained by con- 

 centration and crystallization. 



About the quantitative determination of peptids, V. HENRiQtJES and J. K. 

 Gjaldbak (Ztschr. Physiol. Chem., 61 (1910). Xo. 1, pp. 8-27).— From the re- 

 sults it appears that with the Sorensen formalin titration method (E. S. R., 19, 

 p. 808) it is possible to determine whether a protein which has been treated 



a Compt. Rend. Acad. Sci. I Paris], 147 (1908), p. 1323. 



