_Manipulation._—Place twenty grams of substance in a mortar together with some cold distilled water or pure rain water, stir, and decant the water and suspended matters into a liter flask. After this has been repeated several times, rub up the residual mass and wash it all into the flask. Fill up to about 900 cubic centimeters and allow to stand two hours (twenty-four hours in the case of double phosphates with more than twenty-two per cent of soluble phosphoric acid), shaking repeatedly; or shaking continuously, for half an hour. Fill up to the liter mark and filter through a dry filter. Take portions of twenty-five or fifty cubic centimeters for each determination, add 100 cubic centimeters of molybdate solution for each 100 milligrams of phosphorus pentoxid present, warm to about 80° for an hour, filter, and wash the precipitate with the ammonium nitrate solution. Add a little molybdate solution to the filtrate, warm, and, if a fresh precipitate be observed, it is to be added to the first. The precipitate is to be dissolved in ammonia, and hydrochloric acid carefully added until the precipitate caused by it only slowly redissolves on stirring. The phosphoric acid is precipitated from the clear liquid which is still ammoniacal with magnesia mixture, using ten cubic centimeters for each 100 milligrams of phosphorus pentoxid present. This is added, drop by drop, and the liquid kept stirred during the addition. Allow it to stand at least two hours, filter, wash with dilute ammonia, dry, and ignite. This last is done at first with a very small flame but is finished with the blast-lamp or in a Rössler furnace. To insure burning to whiteness, nitric acid may be used, but not more than one or two drops. _B. Total Phosphoric Acid._—(1) For bone and flesh-meal, fish-guano, and similar fertilizers the reagents necessary are the same as before. Carefully burn five grams to ash, boil the ash for half an hour with nitric acid of 1.32 specific gravity, dilute with water, and, after cooling, dilute to 500 cubic centimeters. Filter through a dry filter and take fifty cubic centimeters of the filtrate. Add 100 cubic centimeters of the molybdate solution for each 100 milligrams of phosphorus pentoxid present. Treat further as before described. (2) Phosphates, guanos, bone-black, etc. One gram of substance, after powdering, and, if necessary, igniting, is covered with four cubic centimeters of hydrochloric acid of 1.13 specific gravity and a little water and heated for an hour and a half. Evaporate to dryness without filtration, making repeated additions of nitric acid until no more vapors of hydrochloric acid are evolved. Boil the residue with nitric acid, cool, make up to 100 cubic centimeters with water, and shake. Filter and treat fifty cubic centimeters of the resulting solution by the molybdate method and proceed further as before described.