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.
83/526 page 59
![45, 46.] obtained. The mother liquor together with the first crop may be used in the preparation of oxalate of potassa or soda. The purified oxalic .Moid is dissolved in 2 parts of distilled water, with the aid of heat, .solution of ammonia added until the reaction is distinctly alkaline, and the vessel put aside in a cold place ; the crystals which form are allowed to drain from the mother Hquor, which, on evaporation, will give another crop of crystals. All the crystals are then purified by recrystallization : 1 part of the. pure salt is dissolved in 24 parts of water for use. Tests.—The solution of oxalate of ammonia should not be pre- cipitated or rendered turbid by sulphuretted hydrogen, or by sulphide of ammonium. When ignited on platinum, the salt must volatilize without leaving any residue. Uses.—Oxalic acid forms insoluble or very sparingly soluble com- pounds with lime, strontia, baryta, oxide of lead, and other metallic oxides; oxalate of ammonia, therefore, produces precipitates of the corresponding oxalates when added to the aqueous solutions of the salts of these bases. In analysis, it serves principally for the detection and separation of lime. § 45. 4. Acetate of Soda, NaO,C,H303 = NaO,! [NaC.H^O,]. Crystallized, NaO,A + 6aq [NaC2H302,3H,0]. Pre2Mration.—Crystallized carbonate of soda is dissolved in a little water, acetic acid added to slight excess, the solution evaporated until ifc crystalhzes, and the salt purified by recrystallization. For use, 1 part of the salt is dissolved in 10 parts of water. Tests.—Acetate of soda should be colourless and free from empyreu- matic matter and inorganic acids. Uses.—The stronger acids in the free state decompose acetate of soda, combining with the base, and setting the acetic acid free. In the course of analysis, acetate of soda is used principally to precipitate ferric phosphate (which is insoluble in acetic acid) from its solution in hydro- chloric acid. It serves also to effect the separation of ferric oxide and alumina, which are precipitated on adding acetate of soda to solutions of their salts and boiling. § 46. 6. Carbonate of Soda, NaOjCO^ [Na^cOj]. Crystallized, N'aO,C02 + lOaq [Na^CO^JOKO]. Preparation.—Commercial bicarbonate of soda in powder is put into a funnel stopped loosely with cotton wool, the surface made level and covered with a disk of difficultly permeable paper with turned-up edges ; it is then washed by pouring small quantities of water on the paper disk, until the filtrate, acidified with nitric acid, is no longer rendered turbid by nitrate of silver solution, or by solution of chloride of barium. The salt is then dried and converted into carbonate by gentle ignition. This is best effected in a silver or platinum crucible or dish; but it may be done also in a perfectly clean vessel of cast iron, or, on a small scale, in a porcelain dish. Pure carbonate of soda may be obtained also by, the repeated recrystallization of commercial carbonate of soda. For use,](https://iiif.wellcomecollection.org/image/b21966953_0083.jp2/full/800%2C/0/default.jpg)
