COLUMBIUM, in mineralogy and chemistry. Mr. Hatchet, in examining some minerals in the British Museum, observed one.which attracted his atten tion, from its resemblance to chromate of iron. On analysing it, he found it to be composed of a metallic acid, united with oxide of iron ; and this acid, by farther experiments, was found to differ in its properties from every other. Mr: Hatchet did not succeed in reducing it to the me tallic state. To the metal, however, which he supposed to be its basis, he gave the name of Coltmbium, as the ore affording it was the produce of America. The mineral which afforded this metallic acid is of a dark brownish grey colour : its lustre is vitreous, inclining to metal lic: its fracture imperfectly lamellated it is moderately hard and very brittle : its particles are not attracted by the mag net: its specific gravity is 5.9. From this mineral Mr. Hatchet extracted the peculiar matter which may be named co lumbic acid. The columbic acid is of a pure white colour, and not extremely heavy ; it has scarcely any taste, nor clots it appear to be soluble in boiling water, but, when placed on litmus paper, mixed with distilled water, soon renders the pa per red.
From the acid solutions of columbic acid, the alkalies throw it down in the form of a white flocculent precipitate. Prussiate of potash changes the colour to an olive-green, and a precipitate of the same colour is gradually form ed. Tincture of galls produces a deep orange-coloured precipitate, especial ly when there is not too great an excess of acid present. Zinc, immers ed in the solution, gives rise to a white precipitate. The fixed alkalies
combine readily, both in the humid and in the dry way, with columbic acid, forming with it salts called columbates. When fused with it, a compound is form ed, which is soluble in water; and if the alkali be in the state of carbonate, the carbonic acid is disengaged during the fusion with effervescence. When a so. lution of potash is boiled on it, a quantity is dissolved; the solution, which has a considerable excess of alkali, affords, by gentle evaporation, a white salt in shin ing scales, having a disagreeable acrid flavour, not soluble very readily in cold water, but, when dissolved, the solution is permanent. Nitric acid added to it precipitates the columbic acid. Prussiate of potash and tincture of galls produced no change ; but when with either of them a few drops of muriatic acid were added, precipitates, similar to those pro duced by these re-agents in the acid so lutions, appeared an olive green with the one, and an orange-coloured precipitate with the other. Hydro-sulphuret of am monia produced a reddish brown precipi tate.
This substance is possessed of proper ties different from any of the known me tals or metallic oxides or acids : for al though in some qualities it approaches to titanium, tungsten, or to molybdena, it differs from them, and from all the others, particularly in the precipitates it affords with prussiate of potash and tincture of galls, in not combining with ammonia, and in being insoluble, and un hlterable with regard to colour, by nitric acid.