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.
158/526 page 134
![OXIDES OF THALLIUM. the dark blackish-green uranoso-uranic oxide. The solutions of oxide of ura- nium in acids are yellow. Sulphuretted hydrogen does not alter them ■ the addition of sulphide of ammonium, after the free acid has been neutralized, throws down a slowly subsiding precipitate, which is readily soluble in acids, even acetic acid; the preciijitation is promoted by chloride of ammonium. The precipitate, when formed in the cold, is chocolate- brown, and contains oxysulphide of uranium, sulphide of ammonium, and water. It is insoluble in yellow sulphide of ammonium; but, whfin. free from other sulphides, it dissolves in colourless or yellow sulphide of ammo- nium containing carbonate of ammonia, yielding a black solution. By washing, the precipitate is gradually converted into yellow hydrated uranic oxide. On warming or boiling the mixture of uranium solution and sul- phide of ammonium, the oxysulphide at first thrown down splits up into sulphur and black protoxide, which last is insoluble in the excess of sul- phide of ammonium (Remele). The oxysulphide of uranium (but not the precipitate which has been converted into protoxide and sulphur) dissolves readily in carbonate of ammonia. (This reaction may be used as a means of separating uranium from zinc, manganese, iron, &c.) If the oxysulphide remains long in cont£|.ct with excess of sulphide of ammonium with access of air, it gradually turns blood-red, hyposulphite of ammonia being formed; if air is excluded, however, the product is black. Ammonia, potassa, and soda produce yellow precipitates containing uranic oxide and alkali; these are insoluble in excess of the precipitants. Carbonate of ammonia and bicarbonate of potassa or soda produce yellow precipitates of carbonate of oxide of uranium and alkali, which readily redissolve in a,n excess of the precipitants; potassa and soda throw down from such solutions the whole of the oxide of uranium. Carbonate of baryta completel}'- jDreci- pitates solutions of oxide of uranium, even in the cold (essential difference from nickel, cobalt, manganese, and zinc, and means of separating uranium from these metals). Ferrocyanide of potassium produces a reddish- brown precipitate or coloration (a most delicate test). Borax and micro- cosmic salt give green beads, with uranium compounds in the inner tiame of the blowpipe, in the outer flame yellow beads are obtained, which acquire a yellowish-green tint on cooling. h. Oxides of Thallium. Thallium occurs, but invariably in extremely minute quantities, in many kinds of copper and iron pyrites, in many kinds of crude sulphur, and accumulated in the flue-dust of the lead vitriol-chambers, where the furnaces are fed with thalliferous pyrites. It is occasionally found in commercial sulphuric and hydrochloric acids, and it has been discovered in lepidolite, preparations of cadmium and bismuth, in ores of zinc, mercury, and anti^ mony, in the ashes of plants, and in some saline waters. Thallium is a metal resembling lead, of 11-8-11-9 sp. gr.; it is soft; melts at 285-290°, is volatile at a white heat, and in a current of hydrogen at a red heat, crackling like tin when bent; it does not decompose water, until an acid is added. Dilute sulphuric and nitric acids readily dissolve it, hydrochloric acid dissolves it with difficulty. Thallium forms two oxides, thallious oxide, TIO [TIO], andthallic oxide, TIO3 [TI^Oj]. Thallious oxide is brown and fusiblej when in the melted state it attacks glass or porcelain. It dissolves in water; the solution is colourless, alkaline, caustic, and absorbs carbonic acid; it is also soluble in alcohol. The thallic oxide is insoluble in water and dark violet, its hydrate is brown. Trioxide of thalUum is hardly acted on by concentrated sulphuric acid in the cold, but on heating they combine; on continued heating, oxygen escapes and sulphate of the protoxide is formed. Treated with hydrochloric acid, the trioxide yields the correspond- ing chloride as a white crystalline mass, which yields chlorine and com- pounds of thallious and thallic chlorides when heated. Thallic salts are decomposed by water with separation of hydrated oxide, alkalies throw](https://iiif.wellcomecollection.org/image/b21966953_0158.jp2/full/800%2C/0/default.jpg)
