RECENT WORK IN AGRICULTURAL SCIENCE. 



AGRICULTURAL CHEMISTRY. 



On the atomic weight of nitrogen, D. Berthelot (Compt. Rend. Acad. Sci. 

 [Paris]. l-'f5 {1907). \o. 1, pp. 65-67). — The author gives figures for the 

 atomic weight of nitrogen obtained by various methods, the average of which 

 agi'ees almost exactly with the atomic weight reported in 1898, viz, 14.005. 



lodometric determination of ammonia, P. Artmann and A. Skrabal {Ztschr. 

 Analyt. Chem., ^6 (1907), pp. .5-17 ; abs. in Jour. Chem. Soc. [London], 92 

 (1907), No. 533, II, p. 196). — In the method proposed an excess of sodium 

 hypobromite of known strengtli is added to the ammonia or ammonium salt 

 and the undecomposed hypobromite is determined in the usual way by adding 

 potassium iodid and dilute sulphuric acid and titrating with standard thiosul- 

 phate, using starch as an indicator. 



The recovery of albuminoid ammonia from distillates contaminated with 

 permanganate, F. E. Hale (.Jour. Amer. Chem. Soc, 29 (1907), No. 7, pp. 1085- 

 10S7). — "The method, which is entirely of a chemical nature, consists in 

 reducing the permanganate by an alkaline sulphite solution, oxidizing the 

 manganous salt to the hydrated peroxid, filtering off the manganese on a 

 carefully washed filter paper, nesslerizing the filtrate, and reading in the 

 usual manner." 



Separation of potassium from sodium as potassium platinum chlorid, 

 J. Morozewicz (Bui. Arad. Sci. Cracow, 1906, pp. 796-803; abs. in Jour. Chem. 

 Soc. [London], 92 (1907), No. 535, II, p. 396.) — It is stated that since sodium 

 platinum chlorid dissociates to some extent in absolute alcohol, forming sodium 

 chlorid, which is practically insoluble in absolute alcohol, the weight of potas- 

 sium platinum chlorid obtained by washing with the strong alcohol is found to 

 be too large. Dissociation does not occur to an appreciable extent when 80 per 

 cent alcohol is used, and correct results can, therefore, be obtained when this 

 strength of alcohol is employed. Accurate results can l)e obtained with absolute 

 alcohol if about 4 times the theoretical amount of acid platinum chlorid is used. 



The determination of phosphoric acid in fertilizers, F. Mach (Landw. 

 Vers. Stat., 66 (1907), No. 1-2. pp. 1-62: abs. in .Jour. Chem. Soc. [London], 92 

 (1907), No. 535, II, p. 395; Chem. Abs., 1 (1907), No. 13, p. 17.55).— In this arti- 

 cle comparisons of the AVagner, Neumann, von Lorenz, and German official 

 methods for the citric acid soluble phosphoric acid in Thomas slag, and of the 

 von Lorenz. Schenke, and citrate methods for total phosphoric acid in Thomas 

 slag superphosphate and ammoniated superphosphate are reported, and the lit- 

 erature of investigations relating to various volumetric methods of determining 

 phosphoric acid is very fully reviewed. There was close agreement in the case 

 of citric acid soluble phosphoric acid in Thomas slag between the results 

 obtained by the Wagner method and the official method with separation of 

 silica, provided evaporation was not carried too far. In case Of total phosphoric 

 acid in Thomas slag the citrate and von Lorenz methods gave closely agreeing 



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