Licence: Public Domain Mark
Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![§^ so, 81.] CARBONATE OF SODA. 79- § 80. 6. Acid Sulphate of Potassa, KO,IIO,2S03 [KHSO,.]. Freparation.—87 parts of neutral sulphate of potassa (§ 42) is mixed with 49 parts of pure concentrated sulphuric acid in a platinum dish or large platinum crucible, and heated to low redness until the whole is in a state of calm fusion ; it is then poured out into a platinum dish placed in cold water, or on to a piece of porcelain, and the cake broken up mto smaller pieces and kept for use. Tests.—Acid sulphate of potassa should dissolve in water with ease to a clear liquid with a strongly acid reaction. The solution should not be rendered turbid or precipitated by sulphuretted hydrogen or by ammonia and sulphide of ammonium. ITses.—Acid sulphate of potassa at the temperature of fusion dis- solves and decomposes many compounds, which cannot be dissolved and decomposed by acids in the wet way without considerable difficulty, such as ignited alumina, titanic acid, chrome iron ore, &c. This reagent, therefore, is useful for dissolving or decomposing such substances. It is better to do the fusion in platinum vessels. II. Blowpipe Reagents. § 81. 6. Carbonate of Soda, KaO,GO, [Na.COj. Preparation.—See § 46. Uses.—Carbonate of soda is useful, in the first place, to promote the reduction of oxidized substances in the inner flame of the blowpipe. In fusing, it brings the oxides into the most intimate contact with the char- coal support, and enables the flame to embrace every part of the sub- stance under examination. With salts of the heavy metals the reduction is preceded by separation of the base. It co-operates in this process also chemically by the transposition of its constituents (according to E.. Wagner, in consequence of the formation of cyanide of sodium). Where the quantity operated on is very minute, the reduced metal is often found in the pores of the charcoal. In such cases, the parts sur- rounding the cavity which contains the substance are scooped out with a knife, and triturated in a small mortar; the charcoal is then washed off from the metalhc particles, which now become visible either in the form of powder or as small spangles, as the case may be. Carbonate of soda serves, in the second place, as a solvent. Platinum wire is the most convenient suj)port for testing the solubility of svib- stances in melted carbonate of soda. A few only of the bases dissolve in fused carbonate of soda, but acids dissolve iu it with facility. Car- bonate of soda is also applied as a decomposing agent and flux, more particularly to effect the decomposition of the insoluble sulphates, with which it exchanges acids, the newly-formed sulphate of soda being reduced at the same time to sulphide of sodium; also to effect the decomposition of sulphide of arsenic, with which it forms a double sulphide of arsenic and sodium, and arsenite or arsenate of soda, thus](https://iiif.wellcomecollection.org/image/b21966953_0103.jp2/full/800%2C/0/default.jpg)
