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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![h. Reactions with, alkalies.—Eecently precipitated hydrate of titanic acid is almost absolutely insoluble in solution of potassa; if titanic acid is fused -with hydrate of potassa and the fused mass treated with water, the solution contains a little more titanic acid. By fusion with carbon- ates of the alkalies, neutral titanates of the alkalies are formed, with expulsion of carbonic acid ; water extracts from the fused mass free alkali and alkaline carbonate, leaving behind acid titanate of the alkali; this is soluble in hydrochloric acid. Titanic acid mixed with charcoal and heated to redness in a stream of chlorine, gives chloride of titanium, a volatile liquid which emits copious fumes in the air. Microcosmic salt, dissolves titanic acid in the point of the outer blowpipe flame to a colourless bead, but with dif- ficulty ; in front of the point of the inner flame, titanic acid dissolves readily and in considerable quantity. If the clear and colourless bead is again: held in the point of the outer flame, it becomes opaque if sufficiently saturated, and by the continued action of the flame titanic acid will separate in mici'oscopic crystals of the form of anatase (G.Rose). According to A. Knop the crystals are phosphate of titanic acid, but according to G. Wunder they are rhombohedral, and consist of phosphate of titanic acid and soda. If the bead is held in a good reducing flame for some time, it will appear yellow while hot, red while cooling, and violet when cold. The reduction is promoted by the addition of a little tin. If some ferrous sulphate is added, the bead obtained in the reducing flame will appear blood-red. 9. Tantalic Acid. Tantalum forms with oxygen tantalic acid, TaOj [Ta205], and tantalic oxide, Ta04 [TaO,]. Tantalic acid occurs in columbite and tantalite (almost always in conjunction with niobic acid). Tantalic acid is white, pale yellow- ish when hot (difference from.titanic acid); when separated in the wet way, it contains water of hydration. The anhydrous acid has a sp. gr. of 7'0 to 8-25. Tantalic acid is not reduced by ignition in a current of hydrogen. It combines with acids as well as with bases. a. Acid solutions.—When the acid is intimately mixed with charcoal, and ignited in a current of dry chlorine, chloride of tantalum, TaClj [TaOIJr is formed; this is yellow, solid, fusible, and can be sublimed; it is completely decomposed by water, with formation of tantalic acid; it is_entirely soluble in sulphuric acid, almost entirely soluble in hydrochloric acid, and partially in potassa solution. If titanic acid be present, on heating the_ mixture of acids with charcoal in a current of chlorine, chloride of titanium will be formed and will fume strongly in the air. Hydrated tantaHc acid dissolves in hydrofluoric acid, and the solution when mixed with fluoride of potas- sium yields avery characteristic salt in fine needles,2KF,TaF5 [K2TaF,],which is distinguished by its sparing solubility in water acidified with hydrofluoria acid (1 of the acid to 150 or 200 of water). Hydrochloric and concentrated sulphuric acid do not dissolve the ignited acid. With bisulphate of potassa, it fuses to a colourless mass ; if this is treated with water, the tantahc acid combined with the sulphuric acid remains undissolved (difierence between tantalic acid and titanic acid; but this cannot be made the basis of a method of separation). When ignited in an atmosphere of carbonate of ammonia, the sulphate of tantalic acid is converted into pure tantalic acid. If a solu- tion of alkaline tantalate is mixed with hydrochloric acid in excess, the first- formed precipitate redissolves to an opalescent liquid; on adding ammonia or sulphide of ammonium to this, the hydrate or an acid tantalate of ammonia is thrown down, but tartaric acid prevents the precipitation. Sul- phuric acid precipitates sulphate of tantalic acid from the opalescent liquid. When acid solutions of tantalic acid are brought into contact with zinc, no blue coloration is observed (dift'erence between tantalic acid and niobic acid). I. Behaviour with alkalies.—By conlinned fusion with hydrate of potassa, tantalate of potassa is formed; the fused mass dissolves in water. If hydrate of soda is used, an opaque melt is obtained; a little water 1](https://iiif.wellcomecollection.org/image/b21966953_0140.jp2/full/800%2C/0/default.jpg)
