4 4. C,H2O, precipitates the oxalate, insoluble in excess, but soluble in HCl. 167. DIDYMIUM. D, c.w. 95. I. (NH)HO produces a precipitate of a basic salt, insoluble in excess of the reagent, but sparingly soluble in NH4Cl. 2. KHO precipitates the hydrate (white), which does not alter on exposure to air. 3. (NH4)2CO3 produces a white precipitate, insoluble in excess of the reagent, but soluble in NHCI. 4. C2H2O4 produces an almost complete precipitation of the oxalate, soluble in hot HCl. 5. Fused with microcosmic salt in the reducing flame, a reddish violet bead is obtained. 6. Fused with carbonate of soda in the oxidizing flame, greyish white beads are obtained. 168. TITANIUM. Ti, c.w. 50. 1. (NH)HO or (NH4)2S precipitates H,TiO, (titanic acid), insoluble in excess of either reagent. 2. KHO also precipitates H2TIO, insoluble in excess. 3. BaCO3 produces the same precipitate. 4. Na,SO, when boiled with titanium solutions precipitates them completely. 5. Zn produces, first a blue coloration, then a blue precipitate, which ultimately becomes white. 6. Fused with FeSO4 and microcosmic salt in the reducing flame, a bright red bead is obtained. Reactions of the Rare Metals precipitated as Sulphides on adding HC1 to the filtrate from the Iron Group. 169. VANADIUM. V, c.w. 51°3. 1. H,S produces no precipitate in acid solutions, but a blue coloration by reducing to a lower oxide. 2. (NH4)2S produces in a solution containing H2SO a brown precipitate of the sulphide, soluble in excess of the reagent. 3. NH4Cl in solutions of alkaline vanadates, precipitates the metal completely as ammonium metavanadate (white). This precipitate loses ammonia on heating, and leaves a residue of V2OË. 4. K4Fe(CN)6 produces, in acid solutions, a green precipitate, not dissolved by acids. 5. SO2, or oxalic acid, reduces acid solutions of V2O to a lower oxide of vanadium, of a bright blue colour. 6. Zn, added to a solution of V2O, in H2SO (diluted with H2Ỏ), produces a series of changes in colour, and ultimately a violet solution is obtained, which rapidly becomes brown in air by oxidation. Reactions of the Rare Metals found in Potassit m Group. 170. LITHIUM. Li, c.w. 7. 1. Pt.Cl, produces no precipitate. 2. Na2HPO produces, on boiling the solution, a white precipitate of 2 Li,PO, + H2O. The precipitate is soluble in HCl, and is not re-precipitated by (NH4)HO unless the solution be boiled. 3. Lithium compounds tinge the lamp flame bright crimson. 171. CESIUM. Cæ, c.w. 133. 1. PtCl produces a crystalline light yellow precipitate of 2 (CaCl) + PtCl4, insoluble in boiling water. (The corresponding potassium salt is dissolved by repeated treatment with boiling water.) 2. Tartaric acid produces a precipitate of the acid tartrate of cæsium, more soluble in water than the corresponding compound of rubidium. 3. Volatile cæsium salts colour the flame violet. 172. RUBIDIUM. Rb, c.w. 85'4. 1. PtCl produces a crystalline light yellow precipitate of 2 (RbCI) + PtCl, insoluble in boiling water. 2. Tartaric acid produces a precipitate of the acid tartrate of rubidium, which is much more insoluble in water than the corresponding cæsium compound. 3. Volatile salts of rubidium colour the flame violet. |