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.

    23/194 (page 11)
    monia and leaves a white powdery residue of ammonium hvdroeen carbonate. Tests. Residue : Should dissolve completely in 10 parts of distilled water, and leave no residue when heated in a platinum dish. Sulphuric or Hydrochloric Acid: A 5 per cent, solution in water, after addition of slight excess of pure nitric acid, should show no turbidity on addition of barium chloride or silver nitrate, and standing one hour. Iron: A 5 per cent, solution supersaturated with pure nitric acid should show only the faintest pinky tint on the addition of solution of ammonium sulphocyanide. It is desirable to make a blank test with the diluted nitric acid, as this is liable to contain traces of iron, particularly if stored for any length of time after redistillation. Metals: A 2 per cent, solution faintly acidulated with acetic acid should show no darkening with an equal volume of hydrogen sulphide solution. Tarry Substances: A 5 per cent, solution slightly acidified with sulphuric or nitric acid should have no tarry odour, and the solution evaporated to dryness in a porcelain dish should leave a colourless and odourless residue. Trade Varieties. The ordinary ammonium carbonate of commerce in lumps sometimes leaves a minute residue on ignition. It may con- tain small traces of sulphate or chloride, and nearly always shows a distinot pink tint when tested for iron as above. Occasionally distinct traces of tarry substances are present, the odour of which is masked by the strong odour of the ammonia and only detectable by the nose after neutralisation wiou sulphuric acid. The formula usually ascribed to this substance indicates 32‘6 per cent. NH3, but this standard is never attained, 31 per cent, being about the average of good commercial specimens when freed from the efflorescent coat- ing of bicarbonate. Volcanic ammonium carbonate was formerly obtained in making borax from the boric acid of volcanic origin from Tuscany, the ammonia being expelled when the acid was treated with sodium carbonate. It was much prized on account of its freedom from tarry impurities, but is not now a commercial product. AMMONIUM CHLORIDE. NH4C1. White granular or powdery crystals free from odour and soluble in 2 parts of water and in about 50 parts of alcohol. Tests. Residue and Tarry Impurities: 5 grammes moistened with nitric acid and evaporated on a water-bath to dryness in a