RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



Phosphoric acid in the presence of saturated solutions of cal- 

 cium bicarbonate, T. Sghloesing {Co7npt. Rend. Acad. Sci. Paris, 

 131 {1900), JVo. 3, pp. 11(9-153,' Jour. Agr. Prat., 1900, II, No. 3%,xyp. 

 1S8-190; ahs. in Bui. Soc. Chinn. Pari.% 2J^ {1900), No. 16-17, pi?. 709, 

 710). — This ai'ticle reports experiments in which phosphoric acid soki- 

 tions of known strength were added to a clear saturated sohition of 

 calcium bicarbonate, the mixture being agitated by means of a current 

 of air free from carbon dioxid. Free carbon dioxid was gradually 

 evolved, and quantities of the bicarbonate corresponding to the dioxid 

 driven off were decomposed, the phosphoric acid being precipitated in 

 the form of tricaleium phosphate. By gradually increasing the amount 

 of phosphoric acid solution it was possible to precipitate almost the 

 whole of the calcium present, provided the solution was allowed to 

 stand sufficiently long (12 hours). It was shown in these experiments 

 that tricaleium phosphate is ver}- slighth' soluble in water free from 

 carbon dioxid. At 16 to 20*-' C. 1 liter of pure water dissolved 0.71 

 mg. of phosphoric acid. In 1,200 cc. of water, to which had been 

 added 50 ce. of a saturated solution of carbon dioxid, 6.9 mg. of phos- 

 phoric acid was dissolved; in 1,000 cc. of water with 250 cc. of satu- 

 rated solution of carbon dioxid, 18.5 mg. of phosphoric acid; and in 

 1,250 cc. of w^ater saturated with carbon dioxid, 91.9 mg. phosphoric 

 acid. It thus appears that the solubility of the phosphate increased 

 with the proportion of carbon dioxid present in the solvent. Trical- 

 eium phosphate is, however, practicably insoluble in carbon dioxid in 

 a saturated solution of calcium bicarbonate. The bearing of this fact 

 on the action of phosphatic fertilizers in the soil and on the formation 

 of natural phosphate deposits is discussed. 



A method for the rapid gravimetric estimation of lime, W. H. 

 Hess {Jour. Amer. Chem. Soc, m {1900). No. 8, pp. 1^77, -^7<§).— The 

 method proposed is described as follows: 



"The lime in the sample is precipitated and separated as the oxalate in the usual 

 way, and the ignition is carried to the point of removing the filter from the residue 

 of lime. The crucible is allowed to cool partially, when a portion of chemically 

 pure dry ammonium nitrate, approximately equal in bulk to the lime in the crucible, 

 and about twice as much chemically pure fused ammonium sulphate are added. A 

 tight-fitting cover is now placed on the platinum crucible and then gentle heat ib 

 applied. It has been found very convenient to incline the crucible at an angle of 



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