A system of instruction in quantitative chemical analysis / by C. Remigius Fresenius.
- Fresenius, C. Remigius, 1818-1897. Anleitung zur qualitativen chemischen Analyse. English
- Date:
- 1854
Licence: Public Domain Mark
Credit: A system of instruction in quantitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
523/680 page 503
![ANALYSIS OF GALENA. § 208.] beaker, add 10 c. c. of the solution of coppey, mix, and tlien add without delay sulphurous acid, and proceed in all other respects as directed § 114, Appendix. The solution of copper must contain no free nitric, nor free hydrochloric acid; delay in the addition of the sulphurous acid to the mixed solution of copper and iodide of potassium, would affect the accuracy of the results. With due attention to these points, the results are exceedingly accurate. Thus Mr. de Haen obtained 0*3567 grm. of sulphate of copper insteadof 0'35G6,—99*89 and 100*1 of metallic copper instead of 100.* 13. Galena. § 208. Galena, the most widcly spread of the lead ores, contains frequently larger or smaller quantities of iron, copper, silver, and commonly also substances (insoluble in acids) from the matrix in which it occurs. The best way of analysing it, is as follows: Reduce the ore to a fine powder, and dry at 212°. Oxidise a weighed quantity of the powder (from 1 to 2 grammes) with highly concentrated red fuming nitric acid, free from sulphuric acid (see §116, II. a. a.—however, the ore is not exposed in a tube to the action of the acid). If the acid is sufficiently strong, no sulphur will separate. After heating gently for some time, dilute with water, filter, and wash the residue. a. Dry the residue, ignite, and weigh (§ 92, 2). It consists of sul- phate of oxide of lead, mineral admixture from the vein, undecomposed by the acid, silicic acid, &c. Heat the whole, or a fractional part of it, with hydrochloric acid to boiling; let the residuary Sediment subside, and then decant the supernatant clear liquid on a filter; pour a fresh portion of hydrochloric acid over the residue, boil again, let the residuary Sediment subside, and decant, and repeat this Operation until the sulphate of lead is completely dissolved; finally place the residue on the filter, and wash with boiling water until every trace of chloride of lead is removed; dry, ignite, and weigh. Subtract the weight found from that of the original residue : the difference expresses the quantity of sulphate of lead which the latter contained. l>. Evaporate the ßltrate nearly to dryness, to expel the excess of free nitric acid; dilute again with water, and test for silver, with very dilute hydrochloric acid. If a precipitate forms, increase, if necessary, the quantity of the hydrochloric acid, filter the fluid from the precipitate, * I think the strength of Bunsen’s solution of iodine may be determined by this method, with the aid of weighed quantities of pure copper, as accurately as by means of bichromate of potassa (§ 114, Appendix, c. ß.).](https://iiif.wellcomecollection.org/image/b28133742_0523.jp2/full/800%2C/0/default.jpg)
