RFXENT WORK I\ A(;RICULTURAL SCIENCE. 



AGRICULTURAL CHEMISTRY. 



The detection of natural phosphates in phosphatic slags, L. Ledoux (HhL 

 Soc. Chilli. Bel;/., 10 {190')), .Yo. 8-9, pp. 26.'), .iUG). — The author proposes the 

 following method, hased upon the complete solubility of the phosphoric acid of 

 IHire slags in citric acid : Digest o gm. of the fine-ground material in .50 cc. of 

 40 per cent citric acid for one-half hour, shaking every 2 minutes; filter and 

 treat the residue with '1') cc. of 40 per cent citric acid for one-half hour; filter 

 and wash with hot water ; dissolve the residue from the second treatment in 

 nitric acid and test for phosphoric acid with ammonium nitro-molybdate. If 

 the slag has not been adulterated with natural phosphate no reaction for phos- 

 [jhoric acid will be obtained. 



The determination of the actual agricultural value of phosphatic slags, 

 A. GuEGOiRE {liul. Soc. Chilli. BeUj.. 19 (190.')). Xo. 8-9, p. 268).— Analyses of 2.". 

 sami)les of crude slag obtained directly from the works showed 4 to 12 per cent 

 of phosphoric acid. 43 to 55 per cent of total lime, and 0.7 to 7.5 per cent of 

 free lime. The silicic acid content was inversely proportional to that of lime. 

 The solubility of the phosphoric acid in 2 per cent citric acid was 76 to 100 

 per cent. There was apparently no relation between free lime and the citric 

 acid solul)ility of the phosphoric acid. The solubility of the phosphoric acid in 

 ammonium citrate containing fluorlds was 47 to 8G per cent. 



A study of methods of determining phosphoric acid in phosphatic slag 

 and natural phosphates, E. Ruwet (liiiJ. Af/r. [Brussels], 22 {1906). A o. 2. 

 pp. 206-212; abs. in Bui. Soc. Chiin. Bch/., 20 {1906), Xo. 7, pp. 2'//,).— Comi)ara- 

 tive studies are reported from which the author concludes that the precipitates 

 obtained in the Sonnenschein molybdic method contain 'Slg, (POj).. as well as 

 MgXIIJ'Oj. making the factor 0.8102 inapplicable, but that the precipitate 

 obtained in the citro-mcchanical iiictbod pi'esents no such difficulties. 



On niethods of detei'mination of phosphoric acid in artificial fertilizers, 

 P. CiiRisTENSEN (Oiii Metoder til Bestcmmelsc of Fosforsyre i Kunstig Godning. 

 Copciihaf/cii, 190'), pp. 10.5). — A monograph on this subject which was awarded 

 a prize offered by the Royal Danish Academy of Sciences. 



A new modification of the method of determining phosphoric acid as mag- 

 nesium-ammonium phosphate with esiDecial reference to fertilizers, G. 

 .ToRCiEN.SEN {Ztschi: Aiiahjt. Chein., .JJ {1906), Xo. 5-6, pp. 21S-S15; abs. in 

 Chcin. Ccntbl, 1906. II, Xo. ), pp. 859, 360).— The essential feature of the modi- 

 fication of his former method (E. S. R., 10, p. 034) which the author proposes 

 consists of the precipitation of the anunonium-magnesium phosphate in a boiling 

 solution. 



Indirect determination of small amounts of magnesia by weighing the 

 phosphoric acid of ammonium-magnesium-phosphate as phosphomolybdic 

 anhydrid, G. Berju {Chein. Ztg., 30 {1906), Xo. 68, pp. 82 J-.S2 J ) .— Tests of the 

 precautions which must be observed in order to obtain a phosphomolybdic pre- 



207 



