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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![§§ 94, 95.] BARYTA. platiuum. The pi*ecipitate is collected and boiled repeatedly with small quantities of water, to remove the platinochloride of potassium present, examinino- the progress of the purification by means of the spectroscope. For this purpose a small quantity of the pi-ecipitate is rolled up in a piece of moistened filter-paper, a thin platinum wire wound round it, and the paper charred in the point of the flame at as low a temperature as possible ; it is then transferred to the fusing zone, and the flame examined by the spectro- scope. The potassium spectrum v/ill be found to grow fainter and fainter, whilst the spectra of rubidium and cassium will become visible, if these metals are present. The solution filtered off from the original platinum pre- cipitate is evaporated to dryness, the residue heated to low redness in a current of hydrogen, in order to decompose the platinochloride of sodium and the- excess of chloride of platinum; it is then moistened with hydrochloric acid, the acid driven ofi again, and the chloride of lithium finally esti'acted with a mixture of absolute alcohol and ether. The evaporation of the solution obtained leaves the chloride of lithium behind iu a state of almost perfect purity; it may then be further examined and tested. Before drawing from the simple coloration of the flame the conclusion that lithia is present, it is advisable, in order to guard against the chance of error, to test a portion of the residue, dissolved in water, with sulphuric acid and alcohol, to make quite sure that neither strontia nor lime is present. The addition of hydrochloric acid, which is repeatedly prescribed in the above process to precede the extraction of the chloride of lithium with alcohol, is necessary as chloride of Uthium, even at a moderate red heat, is converted by the action of aqueous vapour into caustic lithia, this then attracts carbonic acid, and forms carbonate of lithia, which is insoluble in alcohol. § 94. Second Group. Baryta, Strontia, Lime, Magnesia. FrojJerties of the Group.—The alkaline earths are soluble in water- iu the pure (caustic) state; magnesia, however, is only very sparingly soluble in water. The solutions have an alkaline reaction; the alkaline reaction of magnesia is best observed when it is laid upon moistened test-paper. The neutral carbonates and phosphates of the alkaline earths: are insoluble in water, and the solutions of the salts of the alkaline earths are therefore precipitated by carbonates and phosphates of the alkalies; this reaction distinguishes the oxides of the second group from those of the first. From the oxides of the other groups, they are distingvdshed by their solutions not being precipitated either by sulphu- retted hydrogen, or by sulphide of ammonium. The alkaline earths and their salts are white or colourless, and not volatile at a moderate red heat. The solutions of their nitrates and chlorides are not precipitated by carbonate of baryta. Special Eeactions. § 95. a. Baryta, BaO [BaO]. 1. Baryta is pretty readily soluble in hot water, but rather sparingly so in cold water; it dissolves freely in dilute hydi-ochloric or nitric acid. Hydrate of baryta fuses at a red heat, without losin- its water, but this is given off at a very high temperature (Brligelmann).](https://iiif.wellcomecollection.org/image/b21966953_0117.jp2/full/800%2C/0/default.jpg)
