RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



The determination of phosphoric acid in fertilizers, soils, and ash by 

 direct weighing of the ammonium phosphomolybdate, N. von Lokexz {Landu>. 

 Vers. Stat., 55 {1901), No. 3, pp. 183-220) .—Previous methods based on this principle 

 are briefly discussed and the method proposed by the author described in detail, 

 with an account of investigations of the principles on which it rests and tests of its 

 operation in laboratory work. The reagents required are as follows: (1) Sulphate- 

 molybdic solution, prepared by dissolving 100 gm. of pure, dry ammoninm sulphate 

 in 1 liter of nitric acid, specific gravity 1.36 at 15° C, and pouring into it a solution 

 of 300 gm. of pure, dry ammonium molyt)date in 1 Uter of water, the volume being 

 made up to 2 liters, allowed to stand 48 hours, and filtered; (2) nitric acid of specific 

 gravity 1.2 at 15° C; (3) a mixture containing 30 cc. of sulphuric acid of specific 

 gravity 1.84 in 1 liter of nitric acid of specific gravity 1.2; (4) a 2 per cent solution 

 of pure ammonium nitrate rendered slightly acid by a few drops of nitric acid; (5) 

 alcohol of 90 to 95 volume per cent which leaves no residue on evaporation and is 

 not alkaline; (6) ether which leaves no residue on evaporation, is alcohol-free, not 

 alkaline, and contains little water. Solutions of the substances to be examined are 

 prepared as follows: In case of water-soluble phosphoric acid in superphosphates, 

 dissolve 20 gm. in 1 liter of water and use 10 cc. for the determination. With double 

 superphosphates use 10 gm. per liter and 10 cc. of the solution for the determination. 

 For the determination of citrate-soluble phosphoric acid in Thomas slag, prepare the 

 solution according to Wagner's method and use 15 cc. of the solution for the deter- 

 mination of phosphoric acid; in ca,se of superphosphates, precipitated phosphates, 

 etc., follow Petermann's method, using 10 cc. of the solution for the determination. 

 For citric-acid-soluble phosphoric acid in Thomas slag, prepare the solution according 

 to Wagner's method and use 15 cc. for the determination. For total phosphoric acid 

 in superphosphates and Thomas slag, dissolve 5 gm. in 35 cc. of concentrated sul- 

 phuric acid without addition of nitric acid, or in 100 cc. of nitric acid, make uj) the 

 solution to 500 cc. and use 15 cc. for the determination. In case of bone meal, 

 spodium, mineral phosphate, precipitated phosphate, double superphosjihate, jruano, 

 and all other substances containing more than 10 j)er cent of pho.sphoric acid, dis- 

 solve 5 gm. in 50 cc. of concentrated sulphuric acid, or in 100 cc. of nitric acid, make 

 the solution to 500 cc, and use 10 cc. for the determination. With ground horn and 

 other fertilizers containing less than 10 per cent of total phosphoric acid, dissolve 10 

 gm. of the substance in 50 cc. of sulphuric acid, or 100- cc. of nitric acid, making the 

 solution to 500 cc, and using 15 cc. for the determination. For soils and other sub- 

 stances with less than 1 per cent of total phosphoric acid, treat 25 gm. with not 

 more than 200 cc. of nitric acid, then add about 200 cc. of water, cool, and add 10 

 cc. of concentrated sulphuric acid, make the volume to 500 cc, and use 50 cc. for the 

 determination. If the solution is made with sulphuric acid the alicjuot taken for the 

 determination is made to a volume of 50 cc. with nitric acid of specific gravity 1.2. 

 In all other cases, including water-soluble, citrate-soluble, citric-acid-solul)le phos- 

 phoric acid, as well as solutions in nitric acid for total phosphoric acid, the volume 

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