The solution obtained is diluted to forty cubic centimeters with water and washed into a 400 cubic centimeter flask, making the total volume about seventy-five cubic centimeters. Add strong ammonia, shaking after each addition, until the mass sets to a thick jelly from the ferric hydroxid. Add a few more cubic centimeters of ammonia and shake thoroughly, being sure the ammonia is present in excess. Add next nitric acid gradually, with shaking, until the precipitate has all dissolved; add enough more nitric acid to make the solution a clear amber color. The volume should now be about 250 cubic centimeters. Bring the solution to 85° and add, at once, forty cubic centimeters of molybdate solution of the following strength: Dissolve 100 grams of molybdic acid in 300 cubic centimeters of strong ammonia and 100 cubic centimeters of water, and pour the solution into 1,250 cubic centimeters of nitric acid (1.20); close the flask with a rubber stopper, wrap it in a thick cloth, and shake violently for five minutes. Collect the precipitate on a filter, using pump, and wash with dilute nitric acid (1 HNO₃: 50 H₂O). If a thin film of the precipitate should adhere to the flask it can be removed by the ammonia in the next operation. Wash the molybdate precipitate into a 500 cubic centimeter flask with dilute ammonia (1 H₃N: 4 H₂O), using about thirty cubic centimeters. Add hot dilute sulfuric acid (1 H₂SO₄: 4 H₂O) and cover the flask with a small funnel. Add ten grams of granulated zinc and heat until rapid action begins, and then heat gently for five minutes. The reduction is then complete. During the reduction the colors, pink, plum, pale green, and dark green, are seen in the molybdate solution, the latter color marking the end of the reaction. To remove the zinc, pour through a large folded filter, wash with cold water, and fill up the filter once with cold water. But little oxidation takes place in this way. A port-wine color is seen on the filter, but this does not indicate a sufficient oxidation to make an error. In titrating, the wine color becomes fainter and finally the solution is perfectly colorless and shows a single drop in excess of the permanganate. The permanganate solution, for convenience, is made so that one cubic centimeter is equal to 0.0001 gram of phosphorus. With iron its value is one cubic centimeter equals 0.006141 gram of iron; and one cubic centimeter equals 0.005574 gram of molybdenum trioxid.