RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



The action of water and saline solutions upon certain slightly soluble 

 phosphates. F. K. Cameron and L. A. Hurst {Jour. Amer. Chem. Soc, 26 ( 1904), 

 iVo. 8, pp. 885-913). — The methods used and the results obtained in a study of the 

 action of varying proportions of water and of sodium nitrate and potassium 

 chlorid and sulphate on phosphates of iron and aluminum, and of water, calcium 

 chlorid and nitrate, and potassium chlorid and sodium nitrate on tricalcium phos- 

 phate are given. 



The method used was as follows: "In the majority of cases the procedure em- 

 ployed was to weigh the solid phosphate into a bottle and then add 200 cc. of water 

 or solution. . . . Eight-ounce sterilizer bottles, tightly closed with rubber stoppers, 

 were found to be very convenient. The bottles were completely immersed in a 

 constant temperature-bath which varied less than 1° C. during the experiment. In 

 some cases the bottles were occasionally shaken by hand, but in others they were 

 placed in a submerged rotating cradle, driven by an electric motor, and the contents 

 thus kept constantly agitated. When the solutions had remained in the constant- 

 temperature bath the desired length of time, the bottles were placed in an upright 

 position for 24 hours, or longer, to permit the suspended solid particles to subside, 

 as far as possible, and then the supernatant solutions were passed through filters. 

 An aliquot partof the clear filtrate, usually 100 cc, was then titrated with a standard 

 solution of potassium hydroxid free from carbonates, using phenolphthalein as indi- 

 cator, to determine the ' acidity ' of the solution. . . . The phosphoric acid was then 

 precipitated, in the usual way, as phosphomolybdate, and estimated gravimetrically 

 as magnesium pyrophosphate, or occasionally by titrating the yellow phosphomo- 

 lybdate precipitate with a standard solution of alkali. In a few cases the dissolved, 

 phosphoric acid was present in such small quantities that it was found desirable to 

 estimate it by a colorimetric method." 



The results are summarized as follows: "It appears that the rate of action of water 

 upon phosphates of iron and aluminum, or upon tricalcium phosphate is very slow, 

 so that neither in this investigation nor probably in any yet recorded, have final 

 equilibrium conditions been observed. Free acid accumulates in the solution and a 

 portion of the corresponding base is precipitated. While the free phosphoric acid 

 tends to increase the solubility of the phosphate, the base, even though in solution 

 in correspondingly smaller amounts, exerts a greater effect in decreasing it. Therefore, 

 the addition of increasing amounts of water produces a relatively smaller (though in 

 actual amounts a laiger) solution and decomposition of the phosphate. . . . 



"The presence of potassium chlorid in the solution decreases the amount of 

 phosphoric acid obtained from iron, aluminum, or calcium phosphate. It increases 

 the amount of iron, aluminum, or calcium entering the solution. ... 



"Potassium sulphate, as previously observed by Lachowicz, increases the amount 



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