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.
103/680 page 83
![§44.] REAGENTS IN THE DRY WAY. 4. Fluoride of calcium. This substance is used in quantitative analysis to displace and determine boracic acid; none but perfectly pure fluor-spar (like tbat of Derbyshire), free from any admixture of silicic acid, is applicable for this purpose. The hydrofluoric acid used in analytical investigations for the decom- position of silicates, may be prepared from a less pure kind of fluor-spar than that of Derbyshire. Tests.—The best way of testing the purity of fluor-spar, in case of doubt, is to pulverise it finely, and to treat a weighed amount of the powder with pure concentrated sulphuric acid, in a platinum crucible, at a gentle heat, which is gradually increased to redness; the same Operation being repeated until the weight of the residue remains constant. The fluor-spar may be considered pure if the calculated amount of sulphate of lime is obtained by this process. 5. Sulphate of Magnesia. 6. Sesquichloride of iron. 7. Oxide of lead. Preparation.—Precipitate solution of pure nitrate, or acetate of lead with carbonate of ammonia, wash the precipitate, dry it, and expose the residue to a gentle red heat until complete decomposition is effected. Uses.—Oxide of lead is occasionally used to fix an acid, so as to prevent its expulsion at a red heat. 8. Neutral acetate of lead. 9. Protochloride of Palladium and sodium. B.—REAGENTS IN THE DRY WAY. § 44. 1. Carbonate of soda. 2. Carbonate of soda and potassa. 3. Hydrate of baryta. 4. Bisulphate of potassa. Preparation.—Mix 87 parts of neutral sulphate of potassa (see quali- tative analysis) in a platinum crucible, with 49 parts of pure concentrated sulphuric acid, and heat to gentle redness, until the mass is in a state of uniform and calm fusion. Pour the fused salt into a platinum dish, standing in cold water. After cooling, break the mass into pieces, and preserve for use. Uses.—This reagent serves as a flux for certain native compounds of alumina and oxide of chromium. Bisulphate of potassa is used also, as we have already had occasion to state, for the cleansing of platinum crucibles; for this latter purpose, however, the salt which is obtained as a collateral product in the preparation of nitric acid, will be found sufli- ciently pure. r 9 < » w](https://iiif.wellcomecollection.org/image/b28133742_0103.jp2/full/800%2C/0/default.jpg)
