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.

    721/850 (page 687)
    solution of iodine in iodide of potassium, wMch attacks the metal only. The reduced iron of pharmacy (Ferrum Redachom, B. P.) is in good condition so long as it contains, as shown by this method, half its weight of free metal. Proportional weights of equivalent f[uantities of iron and its salts. Metal Feo 112 Ferric oxide. . . FeoO, 160 Ferric hydrate . . FeaGHO 214 Ferric chloride . . FenCIg 325 Ferric sulphate. . FeoSSOj 400 Ferrous sulphate . 2(FeS0,i, 7H.0) . . 556 ARSENICUM. Arsenic (AsoOg) is usually estimated volumetrically (vide 1^564). With certain precautions arsenicum may also be jTOcipitated and weighed as sulphide (AsoSg). Frocess 1.—The pure, white, massive ai'senic (about 0'2) is dissolved in a flask in a small quantity of water containing bicarbonatfe of sodium or potassium, the liquid being heated. A slight excess of hydrochloric acid is then added, and sul- phuretted hydrogen gas passed through the solution so long as a precipitate falls, the mouth of the flask being stopped by a plug of cotton-wool (to prevent undue access of air and consequent decomposition of the gas, resulting in precipita- tion of sulphur). The mixture is warmed in the flask and carbonic acid gas passed through it until the odour of sulphuretted hydrogen has nearly disappeared; the precipi- tate is collected on a tared filter, washed as quickly as pos- sible with hot water containing a little sulphuretted hydrogen, dried in a water-oven and weighed. 198 parts of arsenic should yield 246 of sulphide of arsenicum. Process 2.—The arsenicum must be present in the arsemc condition. If the operator is not certain that this is the case, the solution must be warmed with a little hydrochloric acid and a few grains of chlorate of potassium added until a distinct odour of chlorous vapour is evolved—which is then allowed