Analytical reagents : standards and tests / compiled by Edmund White.

Date:
1911
Catalogue details

Licence: In copyright

Credit: Analytical reagents : standards and tests / compiled by Edmund White. Source: Wellcome Collection.

    28/194 (page 14)
    tains considerable proportions of magnesia. The British Pharmacopoeia strong solution is described as of sp. gr. 0'891 and containing 32'5 per cent. NH3. A solution of this sp. gr. -will, however, contain only 3T5 per cent. In the U.S.P. a strong solution containing 28 per cent. NH3 is official, and in the Ph. Ger. one containing 20 per cent. NH3. A very crude product ie sold for ice-making. AMMONIUM MOLYBDATE. (NH,)6Mo7024, 4H20. Colourless dense crystalline masses which evolve ammonia on careful ignition and leave a white residue of about 80 per cent, molybdic anhydride. It should dissolve without residue in 10 parts of water. Tests. Phosphate: This test is most important since the reagent is used for the detection and determination of phosphoric acid. Dissolve 5 grammes in 20 mils of water and 10 mils strong ammonia solution. Add this liquid very gradually, with constant stirring, to a mixture of 75 mils each strong nitric acid and water. Warm the product and set aside for one to two hours. No yellow precipitate should be produced. Metals: 1 gramme dissolved in 10 mils of water and rendered distinctly alkaline with ammonia should show no darkening in colour after the addition of 5 drops of am- monium sulphide solution. Sulphates and Chlorides: A 10 per cent, solution acidulated with nitric acid should show no turbidity after the addition of \ its volume of solution of barium chloride or silver nitrate and setting aside two hours. Trade Varieties, The ordinary ammonium molybdate of commerce is usually sufficiently pure for analytical purposes if it has a well-crystal- lised appearance and has only a slight shade of green. AMMONIUM NITRATE. NH4N03. Colourless crystals, readily fusing to a colourless fluid when heated, and freely soluble in water. Tests. Residue and Tarry Impurities: 5 grammes heated cau- tiously with 5 drops of nitric acid in a platinum crucible should melt to a colourless fluid, and on continued heating to a low red heat should leave a residue weighing less than 0‘5 Mg. Sulphates or Chlorides: 10 mils of a 10 per cent, solution faintly acidulated with nitric acid should show only a faint turbidity after addition of 1 mil of solution of barium chloride or 1 mil silver nitrate and standing two hours.