RECENT WORK IN AfxRICULTURAL SCIENCE. 



AGRICULTURAL CHEMISTRY. 



On the theory of indicators and the reactions of phthaleins and their 

 salts. S. F. AcKEE {Anitr. Chein. Jour., 3!) (1908), No. J/, pp. 528-54 '/). — The 

 essential point brought out in this discussion is that "the chief cause of*this 

 color [in case of phenolphthalein and similar compounds] is not the colored 

 quinone group . . . but the double compound formed by the inter- or intramolec- 

 ular union of the quinone complex with the free aniline (or aniline hydroxid) 

 groups of the dyestuff." 



Note on the determination of potash by the perchlorate method in ferti- 

 lizers, soils, manures, crops, etc., V. Schenke (Landw. Vers. Stat., 68 (1908), 

 No. 1-2, pp. 61-65; ubs. in Jour. Chem. Soc. [London'], 9// (1908), No. 5^6, II. p. 

 321; Chem. Zig., 32 (1908), No. 36, Rrpcrt.. pp. 238, 239).— The author calls at- 

 tention to certain difficulties encountered in applying his method (E. S. R., 19, p. 

 613) to the determination of potash in soils rich in lime and in solutions con- 

 taining strong acids, particularly sulphuric acid. To overcome such difficulties 

 he recommends a procedure which is in the main the same as that followed 

 in the modified Finkener platinic chlorid method which he has previously de- 

 scribed. In this the sulphuric acid is removed by evaporation and careful 

 heating over a direct flame, the residue taken up in a small amount of 5 per cent 

 hydrochloric acid, the sulphuric acid precipitated with the smallest possible 

 excess of 10 per cent barium chlorid, and other salts removed by the addition 

 of alkali-free milk-of-lime. After standing about one-half hour an aliquot part 

 of the filtrate fi-om these precipitations is acidified with hydrochloric acid and 

 potash precipitated with 20 per cent perchloric acid. A comparison of this 

 method with the ordinary perchlorate method showed that the modified method 

 gave siimewhat higher results than the original method. 



On the use of nitron for the determination of nitric acid in soils and 

 plants, .7. LiTZENDORFF (Ztschr. Angew. Chem., 20 (1907), No. 51, pp. 2209-2213; 

 ahs. in Jour. Soc. Chcni. Indus., 27 (1908), No. 2, p. S3; Jour. Chem. Soc: [Lon- 

 donl, 94 (1908), No. 5'i'i, II, pp. 130, 131; Bui. Soc. Chim. France, J,, ser., 4 

 (1908), No. 5, p, 34I). — In the use of this method for determining nitric acid 

 in soils 2 kg. of the soil is shaken for 5 hour with 4 kg. of water according to 

 the method of Buhlert and Fickendey (E. S. R., 17, p. 832). To 100 cc. of the 

 solution thus obtained, heated to boiling, 5 to 10 cc. of 10 per cent nitron acetate 

 solution is added and the solution kept in ice or ice water until the precipitate 

 separates out. The precipitate is then collected on a Gooch filter, dried at 110° 

 C, and weighed. When the soil contained less than 20 parts per million of 

 nitric nitrogen it was found desirable previously to concentrate the soil extract 

 by evaporation with the addition of a little sodium hydroxid or calcined 

 magnesia. 



In the determination of nitric acid in mustard 20 gm. of the dried aud fine- 

 ground plant was extracted with 400 gm. of water which was slightly warmed. 



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