Five grams of the finely ground phosphate are fused in a platinum dish with fifteen grams of the mixed carbonates of sodium and potassium and three grams of fine sand. After fusing very thoroughly with a strong heat for a quarter of an hour, the dish is removed from the fire and cooled. Its contents, dissolved in hot water, are then put into a half liter flask, and a considerable excess of ammonium carbonate is added to the liquid. All the soluble silica falls out of solution, and the flask, after cooling, is made up to the mark with distilled water, well shaken, and then set aside for twenty-four hours to settle. At the end of this time 200 cubic centimeters are carefully decanted through a filter; the filter is well washed, and the filtrate, after being nearly neutralized with hydrochloric acid, is treated with an excess of calcium chlorid solution. The precipitate, consisting of phosphate, fluorid, and some calcium carbonate, is allowed to settle, and is then carefully washed with boiling water, first by decantation several times, and finally on the filter. After being properly dried in the gas-oven, calcined, and cooled, the residue is treated with acetic acid, placed upon the water-bath, and evaporated to complete dryness. The calcium acetate is now well washed out by several treatments with boiling water, and the residue is brought upon a filter, dried, calcined, and weighed. The weight represents the calcium phosphate and fluorid contained in two grams of the original sample; and if the calcium phosphate in the residue be determined, according to the usual methods, the difference will be calcium fluorid and may be thus estimated. _Example._—Assuming the calcined residue of calcium phosphate and fluorid in two grains of the original sample to have amounted to one and six-tenths gram and the calcium phosphate in this quantity to have been determined as 1.540 gram, the calcium fluorid is thus proved to be 0.060 gram, and, therefore, 2: 0.60::100: x = 3 per cent calcium fluorid which, multiplied by 0.4897, gives 1.46 per cent of fluorin. The above method, while shorter, is not to be preferred to the Chatard process when great accuracy is desired. All the soluble silica may not fall out of the solution as Wyatt says. Finally the fluorin is calculated from small differences in the weight of very heavy precipitates and all the error of the process may be found affecting the numbers for fluorin. For commercial purposes, however, the method is to be recommended for its comparative brevity. GENERAL METHODS FOR ESTIMATING PHOSPHORIC ACID IN FERTILIZERS.