84. IRON GROUP (III.).—Separation of Iron, Nickel, To the filtrate from the sulphides of the Cu and As groups add (NH4) HO and shake for some time. Filter (preferably by the Bunsen pump). Wash the precipitate with cold Residue. Nis and Cos. Test for Co by borax bead. Dissolve the black residue in H Cl and K CI 03. Boil down just to dryness, di lute with H2O, add KCN in excess, then a drop of acetic acid, boil for a few minutes, add NaClO in excess, and boil again. A black precipitate indicates Nickel. The filtrate from this precipitate may be tested for Co by evaporating to dryness, and fusing in a borax bead. Blue colour indicates METHOD I. Cr Is ABSENT. Boil down with a little KClO3 till it smells of Cl. Add pure NaHO till strongly alkaline. Filter. RESIDUE. Fe2(HO), Mn (HO)2. Wash with hot H2O, dissolve in HCI, add (NH4)HO, and filter. FILTRATE. AJ, Zn. Divide into two parts. 1. Add H2S or (NHAS. A white precitate indicates Zinc. Confirm by flame-reaction. 2. Add H Cl till acid, then (NH4)HO till alkaline. A white precipitate indicates Aluminium. Confirm by flame reaction. Cobalt. F. Cobalt, Aluminium, Zinc, Manganese, and Chromium. (till alkaline) + NH4Cl + (NH4)2S. Warm the mixture gently in a small flask well with H2O, containing (NH4)2S, and finally once with H.O alone. Treat dilute HCl, and filter. (Green or violet if Cr be present. Boil down a portion and test for Cr by borax bead. Adopt Method I. if absent, Method II. if present.) METHOD II. Cr IS PRESENT. Boil down with a little KClO3 till it smells of Cl. Add Na2CO3 or NaHO till just neutral or slightly acid; allow to become perfectly cold. Add excess of BaCO3, place in a flask, cork up and shake well, allow to stand till clear. Filter. Residue. FILTRATE. Fe2(HO), Cr2 (HO), Al2(HO) (also excess of BaCO3). RESIDUE. Fe2(HO)6. Dissolve in H Cl, and test with K4Fe(CN)6. A blue precipitate indicates Iron. Confirm by Reactions of the Metals of the Barium Group. 85. Metals whose carbonates are insoluble in water, and whose solutions are precipitated on the addition of (NH4)2CO3: as, however, the carbonates are soluble in acids, the solution, if acid, must be neutralized by addition of (NH1)HO. Barium, Strontium, Calcium. BARIUM. Ba, c.w. 137. I. (NH4)2CO3 produces a white precipitate of BaCO3, soluble in acids, and to a slight extent in NH4Cl. 2. K¿CO, or Na2CO, produces also a precipitate of BaCO3, insoluble in excess of either reagent. 3. H2SO4 or any soluble sulphate produces, even in dilute solutions, a heavy white precipitate of BaSO4 insoluble in acids, alkalies, or salts of ammonium. 4. CaSO4 or SrSO, produces an immediate white precipitate of BaSO4. 5. H.SiF produces a white precipitate of BaSiF 6. C2(NH4)2O4 produces a white precipitate of C,BaO4, soluble in HCl and in HNO3. 7. K2CrO4 produces a yellow precipitate of BaCrO4, insoluble in C2H4O2, but soluble in HCl and HNO3. 8. Heated in the lamp flame a green coloration is produced, especially on moistening the salt with HCl. 86. STRONTIUM. Sr, c.w. 87'5. 1. (NH4)2CO3 or K2CO3 precipitates white SrCO3, soluble in acids, but less soluble in NH4Cl than BaCO3. 2. H2SO, produces a white precipitate of SrSO which is much less insoluble in H2O than BaSO and it therefore precipitates from dilute solutions only on standing or warming. SrSO, is slightly soluble in HCI. 3. CaSO4 produces, after standing some time, a white precipitate of SrSO4. 4. H2SiF does not precipitate strontium solutions. 5. C2(NH4)2O4 produces a white precipitate of C2SrO4, soluble in HCl and in HNO3, also to a slight extent in NH4Cl, but very sparingly in C2H4O2. 6. K2CrO4 produces, only in concentrated solutions, a yellow precipitate of SrCrO4, soluble in C2H4O2. 7. Heated in the lamp flame a crimson coloration is produced, especially on moistening the salt with HCl. 87. CALCIUM. Ca, c.w. 40. I. (NH),CO, or K,CO, produces a white precipitate of CaCO3, which becomes crystalline on heating. 2. H2SO4 precipitates from strong solutions of calcium salts CaSO4, as a white precipitate, which dissolves in a large excess of water, and also in acids. 3. CaSO, produces no precipitate. 4. H2SiF produces no precipitate. 5. C2(NH4)204 produces, even in dilute solutions, a white precipitate of C,CaO,, soluble in HCl or HNO3, but insoluble in C2H2O, or in C2H402 6. Heated in the lamp flame, a dull red coloration is produced, especially on moistening the salt with HCl. This reaction is imperceptible in presence of Ba or Sr salts. 88.—CALCIUM GROUP (IV.). Separation of Barium, Heat filtrate from iron group, add to the hot solution NH4Cl and and add CaSO4 solution. An immediate precipitate indicates Barium; solution. (Test another portion with Sr SO4 for Ba.) To another portion of Neutralize filtrate with (NH4)HO, and add C2(NH4)2O4. An immediate I. Ba PRESENT. Ca ABSENT. Dissolve the carbonate in HCl, and evaporate to dryness. Treat the residue with strong alcohol. Filter. RESIDUE. Bach Confirm by flame test. Green coloration indi. cates Barium. FILTRATE. Sr. Confirm by lighting the alcoholic solution. |