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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![poured on tWs .ass will f^^T^^^l^^^^ Sf tte tantalate of soda -J^dissolved J^^^^^^J^^^^^ter the removal of soda ; but the tantalate J^^n^ sXtLi of soda to this, the tantalate the excess of soda. On slowly addma; solution oi hu ' ^ ^^ntalates less even in tli fnn^ and does notacquire a blood-red tint on adding feSous sulphate (difference between tantalic acid and titanic acid). 10. Niotoic Acid. Niobinm combines with oxygen in several proportions.^ NbO^ [NbO] and NbO, [NbOJ, are oxides, NbO^ [Nb,OJ (niobic acid) is an acid It is occasionally found in columbite, samarskite, &c., and is usua y accom- panied by taJtalic acid. It is white, but turns transiently yellow when Fgnied (difference between niobic acid and tantalic acid). Its sp gr. hes between 4-37 and 4-53 (difference between niobic acid and tantalic acia) By strTng ignition in hydrogen, the niobic acid is converted into the black mo rNbO 1 Niobic acid combines both with bases and with acids _ a AcS solutions of niobic acid.-Ooncentrated sulphuric acid dissolves the acid on heating, unless it has been too ^'^^^^^ addition of much cold water, a clear solution is obtained. When ^^sed with ^isulphate of potassa, it dissolves readily to a colonrless mass, and on treating the melt with boiling water, niobic acid containing sulphuric ac d remain? undissolved; this, however, is readily soluble in hydrofluoric acid /see below). By mixing niobic acid intimately with charcoal and heatmg it fn a cui;ent of chlSrine, a mixture is obtained of the white infusible, difficultly volatile oxychloride, NbO.Cl^ [NbOCIJ, and the yellow more volatile chloride, NbCl^ [NbCIJ. On treatment with water both compounds give turbid solutions, in which a portion of the niobic acid is suspended, but the larger portion is dissolved. If the compounds are boiled with hydro- chloric acid and water is subsequently added, clear solutions are obtained, which are not precipitated either by boiling or by sulphuric acid m the cold (difference from chloride of tantalum). By igniting niobic acid m the vapour ot chloride of niobium the oxychloride is formed (difference from tantalic acid). From the acid solutions of niobic acid, ammonia and sulphide o± am- monium throw down hydrate of niobic acid containing ammonia; this and generally the unignited forms of niobic acid dissolve in hydrofluoric acid. The solution when mixed with fluoride of potassium gives fluoride ot potas- sium and niobium, KF.NbFg [KNbF„], if hydrofluoric acid is in excess, other- wise it gives a combination of fluoride of potassium and oxyfluoride ot nio- bium, KF,Nb02F3 [KNbOFJ. The latter salt is also obtained when niobate of potassa is dissolved in hydrofluoric acid; it is readily soluble m cold water, i part dissolving in 12-5 parts (difference from fluoride ot potassium and titanium, which requires 96 parts of water, and from fluoride ot potas- sium and tantalum, which requires 200 parts of water). On digesting a hydrochloric or sulphuric acid solution of niobic acid with zinc or tin, it acquires a blue and generally also a brown colour, in consequence of the ■reduction of the niobic acid to lower oxides. In the presence of alkaline fluorides, the reduction does not take place (difference between niobic acid and titanic acid). . h. Alkaline solutions.—With hydrate of potassa niobic acid fuses to a clear mass, soluble in water. Towards hydrate of soda, niobic acid](https://iiif.wellcomecollection.org/image/b21966953_0141.jp2/full/800%2C/0/default.jpg)
