RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



The determination of citrate-soluble phosphoric acid in 

 Thomas meal, J. Freundlich (Chem. Ztg., 22 (1898), No. 92, pp. 974, 

 975). — In a recent article P. Wagner proposed a new method for deter- 

 mining citrate-soluble phosphoric acid in Thomas slag, using citric acid 

 instead of ammonium citrate. He pointed out that care should be 

 taken to prevent the precipitation of silica along with the ammonium- 

 magnesium phosphate, when the magnesia mixture is added. 



This writer calls attention to another adulteration, which Wagner 

 does not mention, viz, iron sulphid. By the action of the citric acid on 

 the sulphids so often present in the slag, hydrogen sulphid is formed. 

 When ammonia is added ammonium sulphid results, which, reacting 

 with iron citrate, forms iron sulphid. To avoid weighing this with the 

 ammonium magnesium phosphate, two precipitations are necessary, the 

 iron sulphid in the first precipitate being oxidized by nitric acid or 

 aqua regia. — J. T. Anderson. 



Reynoso's method of analysis of phosphates, U. Antony and 

 G. H. Mondolfo (Gaz. Chim. Hal., 28 (1898), pp. 142-147; abs. in Jour. 

 Soc. Chem. Ind., 17 (1898), No. 12, p. 1186). — In this method phosphoric 

 acid combined with alkaline earths is removed by treating the ammo- 

 nia precipitate with tin and nitric acid. The precipitate is heated with 

 77 per cent nitric acid and tin foil, cooled, filtered, and excess of ammo- 

 nia added. The precipitate contains all the aluminum present and the 

 filtrate the alkaline earths. 



"From the precipitate which, in presence of phosphoric acid, is formed by tin and 

 nitric acid, concentrated hydrochloric acid dissolves a compound which contains 

 the phosphoric acid in the ratio P0 4 : 7Sn, is soluble in alkalis, precipitated from 

 alkaline solution by carbon dioxid, and is called by the authors phosphostannic 

 acid. Tin and nitric acid react in presence of iron to form a compound slightly sol- 

 uble in hydrochloric acid and soluble in cold alkalis, but precipitated as ferric 

 hydrate, on boiling the alkaline solution. If the reaction takes place in presence of 

 phosphoric acid, ferric phosphostannic appears to be formed." 



A study upon the phosphoric acid dissolved in the soil solu- 

 tions, T. Schlcesing, Jr. (Compt. Rend. Acad. Sci. Paris, 127 (1898), 

 No. 4, pp. 236-239; 6, pp. 327-329). —From a study of various methods of 

 extracting soluble phosphoric acid from soils, the author concludes that 

 shaking a given amount of soil with a fixed amount of water is a more 

 reliable means than leaching with successive portions of water. The 

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