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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![§ 104.] and oxalate of ammonia give the same reactions as with protoxide of Potassa throws down the hydrate, which is insoluble in an excess of the Dreck)itant and does not turn brown in the air. Ammonia precipi- ?L s bSTalt^^^ pass milky through the. filter on washmg. The SpSe Produced by carbonate of ammoma is insoluble m an excess of th^ pfec pitint (difference from protoxide of cerium) If a cold dilute solutS if acetate of oxide of lanthanum is supersaturated with ammonia, the Hmy precipitate repeatedly washed with cold water, and a little lodme in powder addfd, a blue coloration makes its appearance, which gradually ier?ades the entire mixture (characteristic difference between oxide_ of fanthanum and the other earths). Carbonate of baryta completely precipi- tates lanthanum oxide in the cold from solutions of its salts. 7. Oxide of Didymium, DijOa [Di,,03]. This oxide is found associated with oxide of cerium and oxide of lantha- num After intense ignition, it appears white ; moistened with nitric acid, and feebly ignited, it is dark-brown (peroxide) but on intense ignition again becomes white. In contact with water, it is slowly converted into the hydrate; it rapidly attracts carbonic acid; its reaction is not alkabne ; it dissolves readily in acids, and also in boiling chloride of ammonium solution. 1 he soluble salts and also their concentrated solutions have a reddish or pale- violet colour. When the nitrate is heated, it is first converted mto a basic salt (diff-erence from lanthanum), which is gray when hot and also when cold The chloride is not volatile. The saturated solution of the sulphate deposits salt, not at 30°, but on boiling. Potassa precipitates the hydrate, which is insoluble in an excess of the precipitant, and does not alter on exposure to the air. Ammonia precipitates a basic salt, which is insoluble in ammonia, but slightly soluble in chloride of ammonium. Carbonates of the alkalies produce a copious precipitate, which is insoluble _m an excess of the precipitant, even in an excess of carbonate of ammonia (de- ference from cerium), but dissolves slightly in concentrated solutions, ot chloride of ammonium. Tartaric acid prevents the precipitation by alkalies. Oxalic acid precipitates salts of didymium almost completely; the precipi- tate is only sparingly soluble in cold hydrochloric acid, but dissolves readily on warming; with oxalate of ammonia, it behaves like oxide of cerium. Carbonate of baryta precipitates oxide of didymium from its solutions slowly but completely. A concentrated solution of sulphate of potassa precipitates didymium solutions more slowly and less completely than protoxide of cerium solutions. The precipitate (sulphate of oxide of didymium) is insoluble in solution of sulphate of potassa, and in water (Delafontaine), but it dissolves in hot hydrochloric acid with difficulty. Hyposulphite of soda does not precipitate solutions of didymium. . Peroxide of didymium is brown ; it dissolves in hydrochloric acid with evolution of chlorine, and in oxyacids with evolution of oxygen, forming soluble salts of didymium oxide. Oxide of didymium gives with borax in both flames a nearly colourless bead, which has a faint amethyst-red tinge if the quantity of didymium is large. Mierocosmic salt dissolves the oxide in the oxidizing flame to an amethyst-red bead which becomes colourless in the reducing flame. With carbonate of soda in the outer flame, a grayish- white mass is obtained (difference from manganese). The absorption spectrum given by the solution of the salts is peculiarly characteristic for didymium. This was first described by Gladstone, and afterwards by O. L. Erdmann and Delafontaine. Bahr and Bunsen have laid down the exact position of the bands (Zeit. anal. Chem., 5,110). For the separation of cerium from lanthanum and didymium, one of the following methods may be used:—a. The solution of the three metals is nearly neutralized, if acid, without allowing any permanent precipitate to form, a sufficient quantity of acetate of soda and an excess of hypochlorite QUAL. I](https://iiif.wellcomecollection.org/image/b21966953_0137.jp2/full/800%2C/0/default.jpg)
