water. both in the form of sesquisalt, their solution is nearly neutralised (if necessary) with sodic carbonate, and largely diluted* with A slight excess of hyposulphite of sodium is added in the cold; (if it be added to a hot solution some ferric hydrate would be precipitated;) and the whole boiled as long as sulphurous anhydride is evolved. The precipitated alumina, which is pulverulent, not gelatinous, is filtered off, washed, freed from sulphur by heating moderately, ignited, and weighed. The filtrate containing all the iron is concentrated by evaporation, and boiled with hydrochloric acid and chlorate of potassium till the separated sulphur is bright yellow, and begins to agglomerate: it is then diluted, filtered from the sulphur which is thoroughly washed, and precipitated by ammonia. Aluminium is always estimated as alumina. It is precipitated as hydrate by sulphide of ammonium (which is better than ammonia or carbonate of ammonium): if the solution contain any alkaline-earthy metals, the access of air must be prevented as far as possible, otherwise these metals may be partly precipitated as carbonates. The hydrate, when dried and ignited, yields pure alumina, Al403. 2. Glucinum or Beryllium. G. Atomic weight, 47. A rare metal, found chiefly as silicate, in some minerals. It is a white very light metal, which, when heated in the air or in oxygen, becomes coated with a thin film of oxide, which protects it from further change. It is soluble in hydrochloric or sulphuric acid: insoluble in cold, slowly soluble in boiling, nitric acid: soluble in potash, but not in ammonia. (Debray. Ann. Ch. Phys. [3.] xliv. 5). OXIDE OF GLUCINUM. Glucina, G2O.-A white powder, obtained by igniting the carbonate. It is soluble in acids, forming salts of glucinum. These closely resemble aluminium-salts in their reactions: there are, however, the following differences between them. Acid sulphate of potassium forms no crystals with glucinum-salts: neither does carbonate of barium precipitate them in the cold. Alkaline carbonates precipitate carbonate of glucinum, soluble in excess (especially of carbonate of ammonium): the solution is reprecipitated on boiling. Potash precipitates hydrate of glucinum, soluble in excess, reprecipitated on prolonged boiling. Hydrate of glucinum is soluble in boiling chloride of ammonium, ammonia being evolved. When treated with nitrate of cobalt before the blowpipe, glucinum-salts give, not a blue, but a grey colour. * 50 cc. solution should not contain more than 0·1 grm. alumina. Separation and estimation of Glucinum.-Native glucinum-compounds (beryl, emerald, euclase, phenacite, &c.) are completely decomposed by fusion with three or four times their weight of carbonates of potassium and sodium. Glucinum is separated from all the preceding metals in the same manner as aluminium. From iron it may also be separated by carbonate of barium. From aluminium it is separated by carbonate of ammonium ; or by boiling the potash solution of the two hydrates; or by carbonate of barium. 3. Zirconium. Zr. Atomic weight, 22.4. A rare metal, found as silicate in some minerals (zircon, &c.). It is obtained as a black powder, which burns with a bright flame when heated in the air. It is scarcely soluble in any acids except hydrofluoric acid. OXIDE OF ZIRCONIUM. Zirconia, Zr2O.-A white powder, obtained by the combustion of zirconium in the air; also by igniting the hydrate. After ignition it is soluble in no acids but strong boiling sulphuric acid. The hydrate is readily soluble in acids, forming zirconium-salts. Sulphate of potassium precipitates a white sulphate of zirconium and potas sium, insoluble in water, and, if precipitated from a hot solution, insoluble in hydrochloric acid. Oxalic acid precipitates white oxalate, insoluble in excess, difficultly soluble in hydrochloric acid. Alkalis and alkaline carbonates give white precipitates insoluble in excess, except in excess of carbonate of ammonium : the solution is reprecipitated on boiling. Separation and estimation of Zirconium. Native zirconium compounds are decomposed by fusion with carbonate of sodium. The fused mass is treated with water, which dissolves the alkaline silicate, leaving a crystalline residue of silicate of zirconium and sodium, from which the silica is removed by evaporation to dryness with hydrochloric acid. After filtering off the silica, the zirconium is precipitated as hydrate by ammonia. From most of the preceding metals of this group, zirconium may be approximately separated by the solubility of its hydrate in carbonate of ammonium. From aluminium it may be separated by potash. From manganese by ammonia in presence of chloride of ammonium. From glucinum, according to Berthier, by suspending the hydrates in water, passing sulphurous anhydride into them till they are completely dissolved, and boiling the solution: when the zirconium is precipitated as a basic sulphite, while the glucinum remains dissolved. None of these separations are complete. Zirconium is estimated as oxide. It is precipitated as hydrate by ammonia, and the precipitate on ignition yields pure zirconia. 4. Thorium. Th. Atomic weight, 59.5. A very rare metal, only found in thorite, monacite, and pyrochlorite. It is obtained as a black powder, which burns brilliantly when heated in the air. It is most soluble in hydrochloric acid. OXIDE OF THORIUM. Thoria. Th2O.-A white powder, obtained by The the combustion of the metal in the air, or by igniting the hydrate. After ignition it is soluble only in strong boiling sulphuric acid. hydrate is readily soluble in acids, forming thorium-salts, which closely resemble zirconium-salts in their reactions. The double sulphate of thorium and potassium differs from the corresponding zirconium-salt by being soluble in hot water. It is insoluble in a saturated solution of sulphate of potassium. Separation and estimation of Thorium.-Thorium may be separated from the preceding metals, except zirconium, by completely saturating their solution with sulphate of potassium. The precipitate is dissolved in hot water, and the thorium precipitated as hydrate by ammonia. From aluminium and glucinum it is also separated by potash. No method is known for separating it from zirconium. Thorium is estimated as oxide. It is precipitated by ammonia as hydrate, which on ignition yields pure oxide. Thorite is completely decomposed by digestion with concentrated hydrochloric acid. Y. Atomic weight, 35. 5. Yttrium. Terbium. Tr. Erbium. E. } Atomic weight not determined. These very rare metals exist in a few minerals (gadolinite, orthite, yttrotantalite). They are scarcely known in the metallic state. Their oxides, yttria, Y2O, terbia, Te2O, and erbia, E2O, always occur together, and no method for their separation is known. They differ from most other earths in being readily soluble in acids after ignition. Yttria and terbia are white erbia is dark-yellow. They are insoluble in fixed alkalis: soluble in carbonate of ammonium, but less readily than glucina. Oxalic acid gives a white precipitate with their salts, insoluble in water. sulphate of potassium precipitates a double salt, slowly soluble in a large quantity of water, more soluble in a saturated solution of sulphate of potassium. Carbonate of barium does not precipitate them, either in the cold or on heating. Acid Separation and estimation of Yttrium. — Yttrium is separated from aluminium by carbonate of barium. From glucinum by oxalic acid: or better, by calcining the earths with some organic body (e. g. sugar) and heating the mixture in a stream of chlorine, when chloride of glucinum volatilises, while chloride of yttrium remains behind. No method is known for its separation from zirconium and thorium. Ammonia precipitates erbia before terbia, and terbia before yttria: but no complete separation can thus be effected. Yttrium is estimated as oxide, obtained by igniting the hydrate precipitated by ammonia. 6. Cerium. Ce. Atomic weight, 46. Lanthanum. La. Atomic weight, 46. These rare metals are always found together: they occur in a few minerals, the most abundant of which is cerite, a silicate of these three metals, iron, and calcium. Little is known of them in the metallic state, except that they dissolve readily in acids. OXIDES OF ČERIUM. Protoxide, CeO. Sesquioxide, Ce2O3. a. Protoxide of Cerium. Cerous Oxide. Ce2Ó.—It is doubtful whether this compound has been obtained pure. The hydrate is readily obtained by precipitating the chloride with a caustic alkali. It dissolves readily in acids, forming cerous salts, which have the following reactions. Oxalic acid precipitates white oxalate, insoluble in excess, converted by ignition into ceroso-ceric oxide. Acid sulphate of potassium separates gradually a crystalline double salt, nearly insoluble in pure water, quite insoluble in a saturated solution of sulphate of potassium. Alkaline carbonates give a white precipitate, scarcely soluble in excess. (c) Potash precipitates white hydrate, insoluble in excess, converted into yellow sesquihydrate by the action of chlorine or hypochlorous acid. Ammonia precipitates a basic salt. b. Sesquioxide of Cerium. Ceric Oxide. Ce1O3. It is doubtful whether this compound has been obtained pure. The salmon-coloured powder obtained by igniting cerous oxalate or hydrate, is not pure ceric oxide, but a mixture of cerous and ceric oxides (ceroso-ceric oxide), not quite constant in its composition. If oxide of didymium be present, it has a red-brown colour, and dissolves in boiling hydrochloric acid. When pure it dissolves only in strong boiling sulphuric acid, forming a yellow solution, whence potash precipitates a yellow hydrate, which is readily soluble in acids, forming ceric salts. Their solutions are yellow, and are converted into cerous salts by boiling with hydrochloric acid. According to Bunsen (Ann. Ch. Pharm, cv. 1), when dry cerous oxalate is heated with magnesia alba, a cinnamon-brown powder is obtained, which contains all the cerium in the form of sesquioxide. Oxide of Lanthanum, La3O.—A white powder, obtained by igniting the hydrate or carbonate in a covered crucible: ignited in the air it turns brown, probably from the partial formation of a higher oxide. It dissolves readily in acids, even after ignition, forming lanthanous salts: it is also soluble in boiling chloride of ammonium. Potash precipitates white hydrate, completely soluble in chlorine-water, without the formation of any yellow deposit. This is the only reaction in which lanthanum differs from cerium. Lanthanous salts are colourless if quite free from didymium. Oxide of Didymium, Di2O.—A white powder, obtained in the same way as oxide of lanthanum. It is readily soluble in all acids, and in ammoniacal salts. Didymium-salts are rose-coloured, or violet: the hydrate is pale rose-colour. Their reactions closely resemble those of lanthanumsalts. Blowpipe reactions.-All cerium compounds give with borax or microcosmic salt in the outer flame a clear bead, which is dark-red while hot, colourless on cooling: in the inner flame, a colourless bead, or, if excess of oxide of cerium be present, a yellow opaque bead. Lanthanum compounds give colourless beads. Didymium compounds give pale rosecoloured beads in the inner flame. Separation and estimation of Cerium, Lanthanum, and Didymium. — Cerite is decomposed by boiling for some hours in strong hydrochloric acid, silica being separated. The solution is treated with ammonia, which precipitates all the metals except calcium. The precipitate is redissolved in hydrochloric acid, and oxalic acid added in excess, which gives a pale rose-coloured precipitate of oxalates of cerium, lanthanum, and didymium. By ignition this is converted into a red-brown mixture of the three oxides, from which the oxides of lanthanum and didymium may be completely dissolved by boiling for some hours with a concentrated solution of chloride of ammonium (Watts); or by treatment first with dilute, and then with strong, nitric acid (Marignac). This effects a complete separation of cerium from lanthanum and didymium. The only method for separating lanthanum from didymium is one founded on the different solubility of their sulphates: but it is not sufficiently exact for quantitative purposes. The three metals are separated from all the metals of Group II., Subdivision A., by means of a saturated solution of sulphate of potassium. From aluminium, by carbonate of barium. From glucinum and yttrium by sulphate of potassium. From zirconium and thorium (only approximately) by sulphate of potassium. Since the composition of ceroso-ceric oxide, obtained by the ignition of cerous oxalate or hydrate, is not quite constant*, cerium cannot be estimated in this form with perfect accuracy. It is better to precipitate the hydrate by potash, dissolve it in dilute sulphuric acid, evaporate to dryness, and heat the residue to commencing redness, when pure sulphate of cerium, SO+Ce2, is obtained. Lanthanum and didymium are estimated as oxides, obtained by igniting the hydrates or oxalates in a covered crucible. 7. Titanium. Ti. Atomic weight, 50. Occurs as titanic anhydride (rutil, anatase, and Brookite): as titanate of calcium (titanite), of iron (titaniferous iron): as a compound of cyanide and nitride of titanium in bright copper-coloured crystals which are found in blast-furnaces in which titaniferous iron has been smelted. These crystals were supposed, till lately, to be metallic titanium. It is a dark-green powder, which burns very brilliantly when heated in oxygen or chlorine. It is soluble in warm hydrochloric acid. OXIDES OF TITANIUM.-The most important oxide is Titanic Anhydride, TiO2. — A white powder, insoluble in water or acids (except hydrofluoric and strong sulphuric acids) obtained by the combustion of the metal in oxygen, or by igniting titanic acid. Titanic Acid, TiO3H2, is obtained by precipitating a solution of the chloride, TiCl4, by ammonia: it is white, insoluble in water, soluble in acids, even after drying over sulphuric acid. But titanic acid, like silicic acid, appears to exist in an insoluble, as well as a soluble, modification: for when an acid solution of titanic acid is boiled, the titanic acid is reprecipitated, and is insoluble in acids; it is converted into the soluble modification by fusion with acid sulphate of potassium. Both modifications exhibit vivid incandescence when ignited, and are converted into * Bunsen (Ann. Ch. Pharm. cv. 1) states that the composition of this oxide is expressed by the formula CeO1= (Ce3O + Ce1O3). |