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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![SULPHATE OF POTASSA. [§§ 42, 43, 44, here classified hy their acids. With tlie salts of the alkaline earths and those of the oxides of the heavy metals the ease is different; these are not used for their acid, but for their base; we may therefore often substitute for one salt of a base another similar one, as nitrate or acetate of baryta for chloride of barium, (fee. For this reason the salts of the ■alkaline earths and of the heavy metals are classified by their bases. a. Salts of the Alkalies, § 42. 1. Sulphate of Potassa, IvO,S03 t^^^soj. Preparation.—Sulphate of potassa of commerce is purified by re- crystallization, and a solution is made of 1 part of the pure salt in 12 parts of water. Uses.—Sulphate of potassa serves to detect and separate baryta and strontia. It is in many cases used in preference to dilute sulphuric acid, which is employed for the same purpose, as it does not, like the latter reagent, disturb the neutrality of the solution. §43. 2. Phosphate of Soda, 2NaO,HO,PO, [Na.HPO,]. Crystallized, 2mO,HO,P03 + 24aq Na2HPO„12KO]. Preparation.—Commercial phosphate of soda is purified by recrystal- lization, and 1 part of the pure salt is dissolved in 10 parts of water for use. Tests.—Solution of phosphate of soda should not become turbid when heated with ammonia. The precipitates which solution of nitrate of baryta and solution of nitrate of silver produce in it must redissolve completely, and without efiervescence, on addition of dilute nitric acid. Sulphuretted hydrogen should not precipitate or colour the solution either as it is or when acidified, nor yet on warming it. Uses.—Phosphate of soda precipitates the alkaline earths and all heavy metallic oxides by double affinity. In analysis, after the separa- tion of the oxides of the heavy metals, it serves as a test for alkaline earths in general; and, after the separation of baryta, strontia, and lime, as a special test for the detection of magnesia; for the latter purpose, it is used in conjunction with ammonia, the magnesia being precipitated as basic phosphate of magnesia and ammonia. Instead of phosphate of soda, phosphate of soda and ammonia (§ 84) may also be used. §44. 3. Oxalate of Ammonia, 2NHp,cp, [(NHj,c,oa Crystallized, 2NHp,CP(. +2aq [(NHJAO^.H^O]. Preparation.—1 part of commercial oxalic acid (which usually con- tains potassa or soda) is dissolved in G parts of boiling water, allowed to cool, and the solution poured off or filtered from the crystals of oxalic acid, which generally contain quadroxalate of potassa; it is then evaporated and again allowed to cool. The second crop of crystals is practically free from potassa. A third crop equally pure may also be](https://iiif.wellcomecollection.org/image/b21966953_0082.jp2/full/800%2C/0/default.jpg)
