4. For the estimation of iron and alumina in each of the superphosphates the Glaser method is recommended provisionally. =57. Methods for Phosphoric Acid used in the Norway Stations.=[42]—1. _Description of the Method for Total Phosphoric Acid._—For determining the phosphoric acid in bone-meal, fish-guano, and superphosphates, five grams of the substance, with twenty cubic centimeters of nitric acid of 1.42 specific gravity, and fifty cubic centimeters of sulfuric acid of 1.8 specific gravity, are boiled half an hour in a half liter flask, diluted with water, and after cooling, made up to the mark. Fifty cubic centimeters of the filtrate are made alkaline with ammonia, then acid with nitric acid, precipitated with fifty cubic centimeters of molybdic solution for every one-tenth gram of phosphorus pentoxid present, heated over the water-bath for one hour, and allowed to stand twelve hours more, when the supernatant liquid is separated by decantation the precipitate washed thoroughly with dilute molybdate solution (1: 4) dissolved in warm dilute ammonia, and the filter washed with hot water. The ammoniacal solution is neutralized with hydrochloric acid, cooled, mixed, drop by drop, with constant stirring, with from ten to twenty cubic centimeters of magnesia mixture, and after a quarter of an hour one-third the volume of ten per cent ammonia is added. This is allowed to stand two hours, is filtered, washed with five per cent of ammonia until the disappearance of the chlorin reaction, dried, burned in an open crucible over a bunsen, and finally for a quarter of an hour, in a covered crucible heated over the blast. 2. _Water-Soluble Phosphoric Acid._—To twenty grams of the substance in a liter flask, are added 800 cubic centimeters of water, and shaken every fifteen minutes for two hours; the volume made up to the mark and the phosphoric acid in fifty cubic centimeters of the filtrate, equaling one gram substance, is determined as under total. 3. _Reverted Citrate-Soluble Phosphoric Acid._—Two and five-tenths grams substance are rubbed up with water, then washed upon the filter with about 100 cubic centimeters of water, the residue on the filter washed into a flask with a part of the measured citrate solution, and digested one hour at 35° to 40° with 200 cubic centimeters of Petermann’s citrate solution. The water and citrate extracts are made up to a quarter of a liter each, and the phosphoric acid determined in from twenty-five to fifty cubic centimeters, according to the quantity present. _Solutions._ 1. _Molybdate Solution._—375 grams of ammonium molybdate are dissolved in two and five-tenths liters of water, and the solution poured into two and five-tenths liters of nitric acid of 1.20 specific gravity. 2. _Magnesia Mixture._—275 grams of crystallized magnesium chlorid and 350 grams of ammonium chlorid are dissolved in 3250 cubic centimeters of water and filled up to five liters with ammonia of 0.96 specific gravity.