RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



The direct determination of available phosphoric acid, F. P. 

 Veitch {Jour. A'/ner. Ohem. 8oc.,^21 {1899). ^^. m.j^P- 1090-1091^).— 

 The author investigated the cause of the discrepancy between results 

 obtained b^' the Ross direct method,' and the official method, and 

 found it to be due to the fact that no account was taken in the Ross 

 method of the phosphoric acid removed in the w^ater used in washing 

 the citrate-insoluble residue. Tests were made of the citrate and 

 molybdate methods for the direct determination of availa})le phos- 

 phoric acid with results very favorable to the latter method, which 

 was carried out as follows: "The water-soluble, extracted as usual, 

 was received in a Sou cc. flask, graduated roughly at 250 cc. and con- 

 taining 5 to 10 cc. nitric acid. The citrate-soluble was then extracted 

 as usual, the filtrate and washings received in the flasks with the 

 water-soluble. After cooling, the volume was completed, shaken, 

 filtered, and in aliquots of 100 cc. the phosphoric acid was determined 

 . . . the molybdate solution being added directly to the solution with- 

 out destroying the organic matter, but the precipitates were allowed to 

 stand over night before filtering. The determinations were completed 

 as usual." 



Note upon the determination of nitrogen in fertilizers contain- 

 ing nitrates, F. F. Veitch {Jour. Anicr. ChnK. Soc. HI {ls'9,'J), ^"o. 

 12^ P2>- 109If., 1095). — The following modification of the Fields-Gunning 

 method^ has been used by the author with very satisfactory results: 

 "To the nitrate in the digesting flask are added 35 to 40 cc. sulphuric 

 acid containing 31: gm. salicylic acid per liter. Allow to stand in the 

 cold until the nitrate is dissolved. Add 6 or 7 gm. of finely broken 

 potassium sulphid, heat over a low flame for 15 minutes, then over the 

 full tliuno until cleai'. (/ool and distil as usual." 



The gasonietric measurement of nitrites in the presence of 

 nitrates or other soluble salts, .1. (tailiiat {Jour. Pharra. et Chlm., 

 6. .s-6'/'., m {1900), xVvy. l,2>i>. 9-12; ahs. in Chem. iY^?/'.y, 82 {1900). Xo. 

 2126, jjp- S7, 88). — The method proposed is based upon the fact that 

 when a solution of neutral metallic nitrite is added to an excess of neu- 



1 U. S. Dept. Agr., Division of Chemistry Bui. 38, p. 17. 

 2 Jour. Amer. Chem. See, IS (1890), p. 1102 (E. S. R., 8, p. 663). 

 :W6 



