The solutions are thoroughly mixed in a precipitating glass, an excess of ammonia added, and allowed to stand for twelve hours under a bell jar. The phosphoric acid contained in the liquor is separated as ammonium magnesium phosphate. It is collected upon a small filter, washed with a little ammoniacal water, redissolved, and titrated with the uranium solution in the manner already indicated. _Example_: The following is an example of this kind of a determination: (1) One and one-half grams of the superphosphate and distilled water enough to make 150 cubic centimeters. (2) Filter-paper with reverted phosphates, sixty cubic centimeters of ammonium citrate, and a sufficient quantity of distilled water to make 150 cubic centimeters. Aqueous solution (1) 25 cc } } = 0.25 grams of the sample. Citrate solution (2) 25 cc } Add magnesium solution twenty cubic centimeters and ammonia in excess, and allow from twelve to twenty-four hours of digestion, then filter and wash, dissolve and titrate. Required of solution of uranium 8.55 cubic centimeters (1 cubic centimeter = 5 milligrams P₂O₅). Correction 0.20. Remainder 8.35 × 0.005 = 0.04175 gram P₂O₅ for 0.25 gram of the sample. Then 0.04175 ÷ 0.25 = 16.7 per cent. From the above data there would be 16.7 per cent of phosphoric acid soluble in water and in ammonium citrate. If it be desirable to have separately the phosphoric acid soluble in water, a separate precipitation is made of the aqueous solution alone by means of the magnesium citrate solution. The precipitate washed with ammoniacal water is redissolved and titrated in the manner indicated. In subtracting from the figures obtained with the two solutions together the number obtained for the phosphoric acid soluble in water, the number representing the phosphoric acid soluble in ammonium citrate alone, is obtained. It is to be noted that the determinations with uranium require always two successive titrations. It would therefore be an advantage in all operations to precipitate a weight of ammonium magnesium phosphate sufficient for allowing this precipitate to be dissolved and made up to 100 cubic centimeters on which amount it would be possible to execute two, three, or four determinations, and thus to obtain a figure absolutely incontestable.