RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



Analysis of fertilizers, D. Sidersky (Anah/ne des engrais. Paris: Ch. Berangcr, 

 J 901, pp. 240, tigs. i>). — This hook has heen jirepared in accordance with the action of 

 the Second International Congress of Applied Chemistry at Paris in 1896, instructing 

 the author to collect the various official methods of analysis of fertilizers in one pub- 

 lication in the French language. It contains the official methods adopted in France, 

 Belgiiim, Holland, and the Grand Duchy of Luxemburg; Germany and Switzerland; 

 Austria-Hungary; the United States, and Italy. The report of the committee 

 appointed by the Third International Congress at Vienna in 1898 on international 

 methods, which was adopted by the Fourth Congress at Paris in 1900, is also given, 

 with a short account of the Kjeldahl method by Kjtddahl himself. 



A contribution to the improvement of the rapid determination of -wrater- 

 soluble phosphoric acid in superphosphates, L. vox Szell [Laudw.Vers. Stat., 

 55 {1901), No. 4-5, pp. 325-346; a^. in Chan. Zfg., 25 {1901), No. 52, p. 199).— T\\\s 

 is an account of an investigation on 7 different kinds of superphosphate of the influence 

 on the accuracy of the determination of soluble phosphoric acid of (1) lack of uni- 

 formity in the sample, (2) different methods of extraction, (3) imperfect filtration, 

 and (4) errors in the jirecipitation and subsequent operations of the determination. 

 The results show that large errors may be introduced into the determination by lack 

 of attention to any of the points named. Asa result of his work, the author proposes 

 the following method: Grind 20 gm. of the samj)le, which has l)een passed through 

 a 3 mm. sieve, with water in a porcelain or glass mortar until it forms a thick broth. 

 Gradually add more water and decant the solution into a liter shaking flask. After 

 extracting in this way 4 or 5 times wash the insoluble residue into the flask. Fill 

 the flask nearly to the mark and shake for \ to 5 hour in a shaking api)aratus, com- 

 plete the volume to the mark, and filter through double fiJter papers. If a shaking 

 apparatus is not available allow the solution to stand 1 to 2 hours, witli frequent 

 shaking. To 50 cc. of the clear filtrate add, with vigorous stirring, just enough citrate 

 solution (300 gm. citric acid, 1 liter of 24 per cent ammonia, and 3 liters of water) to 

 dissolve the precipitate formed on the first addition of the citrate, then add an addi- 

 tional quantity of the solution equal to one-tenth the amount so used to clear up the 

 solution. Precipitate the phosphoric acid by adding, with constant stirring, the 

 required amount of magnesia mixture, prepared by dissolving 55 gm. of magnesium 

 chlorid and 70 gm. of ammonium chlorid in 650 cc. of water, making the volume to 

 1 liter with 0.96 sp. gr. ammonia, allowing to stand 24 hours, and filtering. Twenty- 

 five cubic centimeters of magnesia mixture is usually sufficient for the precipitation. 

 After standing 6 to 12 hours, or after i to J hour's mechanical stirring and 2 hours' 

 standing, collect the precipitate on a filter, wash with 2^ per cent ammonia until free 

 from chlorids, dry the precipitate at 100 to 120° C, char over a low flame, then ignite 

 strongly for i hour, and weigh. 



On the adaptability of the molybdic method to the determination of citric- 

 acid soluble phosphoric acid in Thomas slag, O. Foerster {CJiem. Ztg., 25 {1901), 

 No. 39, p. 421). — To reduce the precipitation of silicic acid as much as possible the 

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