204 EXPERIMENT STATION EECORD. 



• Gravimetric estimation of nitrites, N. Busvold (Chem. Ztg., 38 (1914), No 

 S, p. 28). — Finding tlie methods of Lunge, Gerlinger, and Fischer unsatisfac- 

 tory, one based on the reaction of nitrous acid with bromic acid was studied, 

 as follows: From 1.4 to 1.5 gm. of silver bromate is dissolved in a 750-cc. 

 Erlenmeyer flask in 100 cc. of water and 110 cc. of twice-normal acetic acid 

 solution is added and heated at 80° C. until solution takes place. Then from a 

 dropping funnel provided with a burette tip, 200 cc. of nitrite solution containing 

 1 gm. of sodium nitrite is allowed to flow dropwise, amid shaking, into the 

 flask until a faint green-colored precipitate of silver bromid is produced. After 

 the funnel has been rinsed out three times with water 30 cc. of sulphuric acid, 

 1:4, at 85° is added, heated until the fluid becomes clear and the precipitate 

 a light yellow, filtered through a Gooch crucible, and washed with 1 liter of 

 boiling water. The silver bromid is dried at 130° and weighed. 



Parallel analyses rarely differed over +0.001, which corresponds to an error 

 of 0.1 per cent, whereas with the Lunge permanganate method it was difficult 

 to get a greater degree of accuracy than 0.3 per cent. Theoretically, above 

 0.907 gm. of silver bromid corresponds to 1 gm. of sodium nitrite, and an 

 equivalent of 0.8936 gm. of silver bromid was found, which equals 98.5 per cent 

 of sodium nitrite. The permanganate method gave 98.3 per cent. 



Observations on the separation and determination of phosphoric acid as 

 ammonium-magnesium phosphate, H. Lescoeue (Bui. Soc. Ind. Xord. France, 

 42 (1914), pp. 93-97; abs. in Ztf^chr. Angew. Chem., 27 (1914), No. 59, Rcfera- 

 tcnteil, p. 459). — ^The first part of this paper deals with the separation of phos- 

 •phoric acid as ammonium magnesium phosphate. Attention is called, to Varing- 

 ton's method in which the precipitation of calcium, iron, and. aluminum phos- 

 phates with the magnesium phosphate is prevented by the addition of citric 

 acid. The process as conducted by Joulie is described. 



The second portion of the paper, which deals with the weighing of phosphoric 

 acid as ammonium magnesium phosphate, emphasizes the fact that the phos- 

 phate precipitates often contain an excess of magnesium. The quantity of 

 magnesium chlorid solution used in the precipitation is in direct proportion 

 to the magnesium content of the precipitate. If, however, the precipitate is 

 dissolved in hydrochloric acid and reprecipitated with ammonia, the pure sub- 

 stance is obtained. 



The chemical analyses of soils, A. Mitscheblich (Internal. Mitt. Bodenk., 

 4 (1914), No. 4-5, PP- 327-335). — A discussion of existing chemical methods of 

 soil analyses. 



The continuous extraction methods are given the preference, because they 

 employ the same strength of acid throughout the entire procedure and have no 

 interference from salts which have previously gone into solution. The author's 

 carbonic-acid-extraction method is discussed in this connection. Before an inter- 

 national method is accepted it is held that we must be sure that it rests on a 

 plant physiological basis, and the results obtained by it must bear some rela- 

 tion to crop yield. The author's quantitative formulation of the law of mini- 

 mum is proposed as a basis for such a method. It is said that most of the 

 methods in use for determining the permeability of soils by water do not give 

 duplicate results. 



Contribution to the complete chemical analysis of soils, A. A. J. von 'Sig- 

 MOND (Internat. Mitt. Bodenk., 4 (1914), No. 4-5, pp. 336-362). — It is stated 

 that extraction of soil with boUing concentrated hydrochloric acid for two hours, 

 or with sulphuric acid, will not sen-e as a measure for determining weathered 

 soil constituents (weathering complexes, weathering silicates, soil zeolites, or 

 zeolitic soil constituents). Sandy grains of soil from 2 to 0.02 mm. in size 



