Chemistry : general, medical, and pharmaceutical including the chemistry of the British Pharmacopœia a manual on the general principles of the science, and their applications in medicine and pharmacy / by John Attfield.

  • Attfield, John, 1835-1911.
Date:
1881
Catalogue details

Licence: Public Domain Mark

Credit: Chemistry : general, medical, and pharmaceutical including the chemistry of the British Pharmacopœia a manual on the general principles of the science, and their applications in medicine and pharmacy / by John Attfield. Source: Wellcome Collection.

    727/850 (page 693)
    and all excess of the nitrate has been decomposed. Cool and weigh the resulting oxide (PbO). Process 2.—Dissolve 04 or 0'5 of a gramme of acetate of lead in a small quantity of water, drop in diluted sulphuric acid, add to the mixture twice its bulk of methylated spirit of wine, and set aside. Decant the supernatant liquid, collect the sulphate on a filter, wash with spirit, dry, transfer to a porcelain crucible, removing as much of the sulphate as possible from the paper, incinerate on the crucible-lid (not in a platinum coil, for the particles of reduced lead would unite with the platinum by fusion), ignite, cool, and weigh. Process 3.—About half a gramme of acetate of lead is dis- solved in two or three hundred c. c. of water, acetic acid added, and then solution of red chromate of potassium. Collect the precipitate on a tared filter, wash, dry at 100° C, and weigh. Process 4.—In certain cases, notably in that of commercial white lead, the lead may be estimated in the metallic state by means of cyanide of potassium. The lead paint (about 20 grammes) is weighed and carefully incinerated. The residue, a mixture of metallic lead and oxide of lead, is then mixed with several times its bulk of cyanide of potassium and the whole heated to fusion. With careful manipulation the lead collects in one globule, which, after cooling, may readily be separated from the mixed cyanide and cyanate and weighed. Commercially pure white lead should yield 74 per cent, of lead. Molecular weights of salts of lead. . Pb 207 Acetate. . . Pb2Cc,H30o, 3HoO . . 379 Oxide . . . PbO ~ . .' . . 223 Sulphate . . PbSO, 303 Chromate . . PbCrO, . 323-5 SILVEE. Compounds of silver which are readily decomposed by heat are estimated in the form of (1) metal, others usually as (2) chloride (AgCl), but sometimes as (3) cyanide (AgCN).