The flask in which the filter-paper is introduced, together with the ammonium citrate, is stoppered and shaken violently in order to disintegrate the filter-paper and put the reverted phosphates in suspension. There are added then about sixty cubic centimeters of distilled water, and the flask is shaken and left for twelve hours at least, or at most for twenty-four hours. The volume is made up to 150 cubic centimeters with distilled water, and, after mixture, the solution is filtered.
There are thus obtained two solutions which can be precipitated together or separately according to circumstances. The most usual process is to combine the two equal volumes of twenty-five, fifty, or one hundred cubic centimeters, representing one-quarter, one-half, or one gram of the material according to its presumed richness, in a precipitating flask to which are added from ten to twenty cubic centimeters of the solution of magnesia made up as follows:
| Magnesium carbonate, | 50 | grams. | |
| Ammonium chlorid, | 100 | “ | |
| Water, | 500 | cubic | centimeters. |
| Hydrochloric acid, | 120 | “ | “ |
After complete solution of the solid matters in the above, add 100 cubic centimeters of ammonia of 22° strength, and distilled water enough to make one liter.
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.