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.

    96/194
    LEAD. Metallic lead in the form of foil or granulated is sold con- taining less than 5 dwts. of silver per ton, and in this form may be regarded as free from silver for analytical purposes. The determination of silver in such small quantities can only be done by eupellation on large quantities. LEAD ACETATE. Pb(C2H302)23H20. Colourless transparent crystals, easily soluble in water, having a sweetish astringent taste, and a faint acetous odour. The salt effloresces and loses acetic acid on exposure to air becoming thereby partly insoluble in water. Tests. Solubility: 5 Gm. should dissolve in 50 mils freshly boiled and cooled distilled water with only the faintest opalescence, and this should immediately disappear on the addition of one drop of acetic acid. Copper and Iron : 0 5 Gm. dissolved in 10 mils of water and treated with potassium ferrocyanide solution should give a pure white precipitate free from any tinge of blue or brown. Chloride: 1 Gm. dissolved in 20 of distilled water with two drops of acetic acid should give no immediate precipi- tate with silver nitrate solution. Alkalies and Alkaline Earths: Dissolve 2 Gm. in 40 mils of water. Add hydrochloric acid drop by drop until no further precipitate is produced and then remove the re- mainder of the lead from the solution by hydrogen sulphide and filter. The filtrate evaporated to dryness and ignited should yield a residue weighing not more than 1 Mgm. Trade Varieties. The commercial salt is largely used as sugar of lead in medicine and the arts. It usually contains basic carbonate due to dissociation in contact with air, and is therefore not completely soluble in freshly boiled water. It also usually contains traces of iron and copper. LEAD CHROMATE. PibCr04. Heavy yellowish-brown powder or granules of the same produced by partial fusion and stirring.