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.

    27/194 (page 13)
    strongly acidulated with hydrochloric acid should give no turbidity on the addition of barium chloride solution. Metals: The addition of ammonia and ammonium sulphide or an equal volume of hydrogen sulphide solution to a 5 per cent, solution of the salt should not produce a black coloration or turbidity. Trade Varieties. The article described above can only be produced by neutralising very pure hydrofluoric acid with pure ammonium hydroxide or carbonate in a platinum dish. Commercial ammonium fluoride made from crude acid is often colourless, but contains considerable quantities of sulphate, fluosilicate, and lead, as well as arsenic and other impurities. AMMONIUM HYDROXIDE. A solution of ammonia gas in water. In this country Liquor Ammonias Fortis sp. grav. 0'880 is usually sold. This corresponds to a strength of about 35 per cent. NH3, but owing to the ease with which ammonia escapes from such strong solutions the product will usually be found slightly under this strength. Tests. Residue: 20 mils evaporated on a water-bath in a glass dish should leave a residue weighing not more than 0'5 Mg. Pyridine and Tarry Impurities: 10 mils of the liquid is diluted with 40 mils of water, a few drops of methyl orange solution added, and (then sufficient pure nitric acid to nearly neutralise the ammonia. The liquid should not change colour, and should be free from unpleasant odour. On evaporation on a water-bath it should leave a white residue. Chlorides and Sulphates: 5 mils diluted with 20 mils of water and rendered slightly acid with pure nitric acid should show only the faintest turbidity on adding silver nitrate or barum chloride solution, warming, and setting aside for three hours. Carbonate : 5 mils should form a clear mixture with 20 mils of lime water, and even after boiling only the faintest turbidity should be produced. Metals: 5 mils diluted with 25 mils of water should show no discolouration on the addition of 5 drops of ammonium sulphide solution. Other Impurities: The absence of residue exceeding the amount given above will exclude appreciable traces of other probable impurities. Trade Varieties. The ordinary Liq. Ammon. Fort, of commerce is of variable quality. It sometimes shows considerable traces of tarry impurities and traces of iron. The solid residue, when exceeding in amount that mentioned above, often con-