1020] AGRICULTURAL CHEMISTRY — AGROTECHNY. 413 



The quuntitativc determination of boric acid, P. Jannasch and F. Noix 

 (Jour. J'rakt. Clttm., n. ser., 99 (1019), xYo. 1-2. pp. 1-SS, flgx. 2). — A method 

 for the deterniiiiiition of B-Os in salts and niineiaLs is described which de- 

 pends upon the fact that it is completely volatilized in the form of the methyl 

 ester when distilled with methyl alcoliol at from 60 to 90° C. The technique 

 of the procedure as applied to the determination of boric acid in tourmalin 

 is described in detail. 



The determination of dicyandiamid in calcium cyanamid by Care's 

 method, G. Hager and J. Keun (Ztschr. Arujew. Chem., 29 (1916), No. 63, 

 Aufsatzt., pp. 309-312). — A critical study is reported of Caro's method of de- 

 termining dicyandiamid in calcium cyanamid (E. S. R., 25, p. 24). 



Two sources of error in the determination are pointed out. On warming 

 the dicyandianiid-silver solution with potassium hydroxid double decomposi- 

 tion takes place, resulting in a loss of ammonia and nitrogen, and in the precipi- 

 tation of large amounts of cyanamid with silver salts in ammoniacal solution 

 more or less dicyandiamid is brought down at the same time. Botli these 

 sources of error tend to give too low results. 



The determination of dicyandiamid in calcium cyanamid, A. Stutzeb 

 (Ztschr. Angew. Chem., 29 (1916), No. 97, Aufsatz., pp. 417, 4I8).— The author 

 discusses the criticisms of Hager and Ivern, noted above, in regard to Caro's 

 method of determining dicyandiamid, and describes a modification of the method 

 which is considered to eliminate these errors. The method consists essentially 

 in dissolving the material in 94 per cent alcohol, using a portion of the solution 

 to determine the total nitrogen soluble in alcohol, and the remainder to deter- 

 mine cyanamid by precipitation with a silver salt and ammonia and dicyandia- 

 mid by precipitation of the filtrate with sodium hydroxid. 



The technique is described in detail. 



The determination of dicyandiamid in calcium cyanamid, G. Hager and 

 J. Kern (Zt>irhr. An<jew. Chem., SO (1917), No. 17, Auf.satz., pp. 53, 5Jf).— 

 Attention is called to the nythod of determining calcium dicyandiamid in cal- 

 cium cyanamid described by Brioux (E. S. R., 24, p. 323). 



This consists essentially in determining both calcium cyanamid and dicy- 

 andiamid in an aliquot of the solution by precipitation with silver nitrate and 

 potassium hydroxid, and in another portion of the solution determining the 

 cyanamid by precipitation with silver nitrate and ammonia. The dicyandiamid 

 is then determined by difference. The technique of the method is described, 

 and results are reported which are considered to indicate the supex'iority of this 

 method over Caro's method. 



An examination of the method of Stutzer, noted above, is also reported. The 

 authors conclude, however, that it is open to as many sources of error as Caro's 

 method. 



New extraction apparatus, E. Beccard (Chem. Ztg., 43 (1919), No. 113, 

 p. 621, figs. 2; abs. in Chem. Abs., 14 (1920), No. 7, p. 869, fig. i).— Descriptions 

 and illustrations are given of two forms of extraction apparatus in which the 

 solvent is brought into contact with the substance to be extracted several times 

 before siphoning, instead of once as in the ordinary extraction apparatus. One 

 form of apparatus is suitable for extracting an aqueous solution with a solvent 

 of lower specific gra\'ity, and the other for solids or a solution with a solvent of 

 higher specific gravity. 



A photometric turbidimeter, W. G. Bowers and J. Moyer (Jour. Biol. 

 Chem., 42 (1920), No. 1, pp. 191-198, figs. 2).— In the apparatus which is de- 

 scribed and illustrated the photometric oil spot is applied to the turbidimeter to 

 balance intensities of illumination in measuring turbidities. 



