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 filtrate is often brown in presence of Ni. Treat Residue. NiS and COS. Test for Co by borax bead. Dissolve the black METHOD I. Cr IS ABSENT. residue in H CI and K Cl 03. Boil down just to dryness, di Boil down with a little KClO3 till it smells of Cl. Add cess, then a drop of acetic acid, boil for a few minutes, add NaCIO † 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 Cobalt, Wash with hot H2O, dissolve in HCl, add (NH4)HO, and filter. Residue. Fe, (HO) Dissolve in ferric salt, the FILTRATE. Mn. KNO3. A green 2. Add H CI till acid, then (NH4)HO till alkaline. A white precipitate indicates Aluminium. Confirm Co Mn. action. re For the separation of the metals of this group in presence of Phosphoric Acid, &c., see Table L in the Appendix. † NaHO and Bromine water may be used instead of NaClO. 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 H2O alone. The the precipitate with cold dilute HCl, and filter. FILTRATE. Cr, Al, Fe, Zn, and Mn. (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 KCI 3 till it smells of Cl. Add Na2CO3 or NaHO till just neutral or slightly ac.d; allow to become perfectly cold. Add excess of BaCO, place in a flask, cork up and shake well, allow to stand till clear. Filter. RESIDUE. Fe2 (HO)6, Cr2 (HO, Al2(HO) (also excess of BaCO3 A Wash well, boil with pure NaHO, and filter; add HCl to the filtrate, and then (NH4) HO till alkaline. white precipitate indicates Aluminium. Confirm by flame-reaction. Fuse the residue insoluble in NaHO with a mixture of Na2CO3 and KNO3, extract with water, and filter. RESIDUE. Fe2(HO). Dissolve in H Cl, and test with K4Fe(CN)6. A blue precipitate indicates Iron. FILTRATE. Cr. Yellow in colour. Acidify with acetic acid; add lead acetate. A bright vellow precipitate indicates Chromium. ANOTHER METHOD.* Boil filtrate from Cu group to expel H2S, then boil with KCIO3, add NH4Cl, and then (NH4)HO till alkaline. Filter. RESIDUE. Fe, Al, Cr, Test washed ppt. for Cr by borax bead, and for Fe with K4Fe(CN)6. Treat residue with warm NaHO, and test for Al in filtrate as in Method I. 2. FILTRATE. Co, Ni, Mn, Zn, Add (NH4)2S and filter. Separate Co and Ni with HCI as above. Boil filtrate from NiS and CoS, add NaHO till alkaline, and separate Mn and Zn as in Method II. FILTRATE. Zn, Mn. Ba present with well, and filter ; by * When this method is used the filtrate cannot be afterwards tested for potassium. 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 (NH4)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. K2CO, or Na,CO, 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 SrSO4 produces an immediate white precipitate of BaSO4. 6 5. H2SiF 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. I. (NH4)2CO3 or K2CO3 precipitates white SrCO3, soluble in acids, but less soluble in NH4Cl than BaCO3. 2. H,SO, produces a white precipitate of SrSO, which is much less insoluble in H2O than BaSO4, and it therefore precipitates from dilute solutions only on standing or warming. SrSO4 is slightly soluble in HCl. * 3. CaSO4 produces, after standing some time, a white precipitate of SrSO. 6 4. H,SiF does not precipitate strontium solutions. 5. Ca(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. 1. (NH4)2CO3 or K2CO, produces a white precipitate of CaCO3, which becomes crystalline on heating. 2. H2SO4 precipitates from strong solutions of calcium salts CaSO, as a white precipitate, which dissolves in a large excess of water, and also in acids. 3. CaSO4 produces no precipitate. 4. H2SiF produces no precipitate. * 5. C2(NH4)2O4 produces, even in dilute solutions, a white precipitate of C2CaO4, soluble in HCl or HNO3, but insoluble in C2H2O or in C2H4O1⁄2 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. TABLE 88. CALCIUM GROUP (IV.). Separation of Barium, Heat filtrate from iron group, add to the hot solution NH4Cl and and add to a portion CaSO4 solution. An immediate precipitate indicates dilute Barium solution. (Test another portion with SrSO4 for Ba) To and Sr. Filter. Neutralize filtrate with (NH4)HO, and add C2(N H4)2O4 |