. Proceedings of the Twenty-Fourth Annual Convention of the Association of Official Agricultural Chemists held at the Jamestown Exposition, Norfolk, Va., October 9-11, 1907. m th^ precipitated potassium phos-phomolybdate and at the same time dissolve only inappreciable quantities ofthis yellow precipitate. Accordingly a test was made to determine the solu-bility of the potash precipitate in both nitric acid and sodium nitrate underdifferent conditions in respect to strength, time of contact, etc. For this pur-pose a quantity of pure potassium phosphomolybdate was prepared by addingphosphomolyb
. Proceedings of the Twenty-Fourth Annual Convention of the Association of Official Agricultural Chemists held at the Jamestown Exposition, Norfolk, Va., October 9-11, 1907. m th^ precipitated potassium phos-phomolybdate and at the same time dissolve only inappreciable quantities ofthis yellow precipitate. Accordingly a test was made to determine the solu-bility of the potash precipitate in both nitric acid and sodium nitrate underdifferent conditions in respect to strength, time of contact, etc. For this pur-pose a quantity of pure potassium phosphomolybdate was prepared by addingphosphomolybdic acid to excess of potassium sulphate in solution and washingthe precipitate with a weak solution of sodium nitrate. To determine theaction of nitric acid upon this precipitate, gram of potassium phosphomolyb-date was placed in contact with 50 cc of the nitric acid of varying strength,well stirred and filtered. The filtrate was evaporated to dryness on a waterbath and the residue titrated with potassium hydroxid. Table I.—Determination of the soJuhility of the potash preeipitate in nitrie acid. No. Conditions. Amount ofpotassiumhydroxidrequired 1 Heated to 50° C. and cooled 1 hour 2 One hour in cold 3 Five minutes in cold -with constant stirring 4 Ten minutes in cold with stirring :1,00080 :1,000 Heating to 50° C. is thus seen to exert marked solvent action, even withvery dilute solutions of nitric acid. The cold acid of much greater strengthexerts less solvent action, when time of contact is limited. The action of the nitric acid wash under different conditions was also testedon an ofiicial acid (sp. gr. ) extract of soil. Ten cubic centimeters ofsolution, corresponding to 1 gram soil, were evaporated with phosphomolybdicacid and the residue subjected to the following methods of washing: 119 Table II.—Determination of the soJuMUty of the precipitate of an official acidextract of soil in nitric acid. Sample. Conditions. Stre
Size: 1581px × 1581px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1900, bookdecade1900, bookidproceedingsoftwe11wile
