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RECENT WORK IN AGRICULTURAL SCIENCE. 



AGRICULTURAL CHEMISTRY. 



A short and accurate method for the estimation of iron, alumina, and phos- 

 phoric acid when occurring together, T. Cooksky (Jour, and Proc. Roy. Soc. 

 N. 8. Wales, 4I (1901), pp. 163-171; aJ)s. in Jour. Chem. 80c. [London'\, H 

 (1908), No. 533, II, pp. 987, 988).— A combination of well-known volumetric 

 methods is employed as follows: 



" To the sohition, which must be sufficiently acid to produce a yellow color 

 and not a reddish one with the iron present, is added a definite quantity of a 

 standard solution of sodic dihydric phosphate. In case the original solution is 

 too strongly acid, this can be partially neutralized by caustic potash or by 

 evaporation ; and it is convenient to work with 20 or 30 cc. of solution contain- 

 ing not more than 0.1 gm. of the mixed oxids. With this amount of liquid, the 

 precipitation can be conveniently carried out in a 100 cc. flask. Caustic potash 

 of decinormal strength is gradually run in under constant shaking until the 

 pink tint with methyl orange has just disappeared. The volume is made up to 

 80 or 90 cc. and warmed for a short time on the water bath. This heating 

 causes the precipitate to coagulate and quickly settle. The precipitate is now 

 filtered off and well washed with hot water until the filtrate gives no cloudiness 

 with silver nitrate when tested for chlorids, assuming them to be present. A 

 few more washings after this stage is arrived at, thoroughly stirring up the 

 precipitate on the filter, are then sufficient. The filtrate and washings together 

 will then make 200 or 250 cc. Calcium chlorid in excess is added, the whole 

 made slightly acid to methyl orange by a few drops of decinormal hydrochloric 

 or sulphuric acid, and boiled to get rid of any carbonic acid. The procedure 

 is the same as that previously described. The precipitated phosphates are 

 dried, and can be removed from filter paper, the latter burnt off in platinum 

 crucible at low temperature and the remainder of precipitate added. The 

 whole is then heated by Bunsen burner to constant weight. It is perhaps 

 advisable not to raise to too high a temperature. The iron can be separately 

 estimated either in the original solution or by dissolving up the phosphates with 

 a few drops of strong hydrochloric acid and making use of the iodiu and thio- 

 sulphate method. 



" We have now the weight of the total iron and aluminum phosphates, the 

 amount of iron, and the amount of phosphate left in solution. The amount of 

 iron phosphate corresponding to the oxld of iron found, is subtracted from the 

 total weight of phosphates, the difference gives the aluminum phosphate. By 

 subtracting the known quantity of phosphoric acid added from the sum of 

 the three amounts of phosphoric acid found, that is, that combined with the 

 iron, that combined with the alumina, and the amount left in filtrate, we obtain 

 the original phosphoric acid in solution." 



Qualitative analysis of phosphates and other salts soluble in acid media, 



H. Caron and D. Raquet (Ann. Chim. Analyt., 13 (1908), No. 10, pp. 373-378).— 



A systematic plan of procedure is described. 



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