6. KCNS produces even in dilute solutions a bloodred coloration, due to the formation of a soluble iron sulphocyanide. HCl does not destroy the coloration, but it is destroyed by C2H ̧O„Na, HgCl2, HÅPО, and by C1H2O

7. BaCO3 precipitates ferric solutions completely as Fe2(HO) mixed with basic salt.

8. The blow-pipe reactions are the same as for ferrous compounds.

78. NICKEL. Ni, c.w. 587.

1. (NH4)2S produces a black precipitate of NiS, slightly soluble in excess, forming a brown solution from which NiS is precipitated on boiling. The precipitate is very difficultly soluble in HCl, but dissolves in HNO, and in aqua regia.

2. NaHO or KHO produces a light green precipitate of Ni(HO), insoluble in excess of the reagent, and unalterable in air.

3. (NH) HO produces also a precipitate of Ni(HO)2, readily soluble in excess, yielding a blue fluid, which is re-precipitated by KHO or NaHO. Acid solutions, or those containing salts of ammonia, yield no precipitate with (NH1)HO.

4. KCN produces a yellowish green precipitate of Ni(CN)2, soluble in excess to a brownish yellow solution of 2 KCN, Ni(CN)2. This solution is re-precipitated by addition of dilute HCl or H2SO4, and, if boiled with a strong solution of NaClO, yields a black precipitate of Ni,(HO)

5. KNO2, in presence of C2H4O2, produces no precipitate.

6. Fused with borax in the oxidizing blow-pipe flame, yields reddish yellow beads when hot, which become paler on cooling. In the reducing flame the bead becomes grey by the presence of metallic nickel. (See also 59.)

79. COBALT. Co, c.w. 587.

1. (NH4)2S produces a black precipitate of CoS, insoluble in excess of the reagent and in HCl, but soluble in aqua regia.

2. KHO or NaHO precipitates blue basic salts, which turn green on exposure to air by oxidation. On heating the precipitate is converted into red hydrate Co(HO)2, which is soluble in (NH4)2CO3to a reddish violet solution.

3. (NH4)HO produces the same precipitate as KHO, soluble in excess, yielding a reddish brown fluid, which is re-precipitated by KHO or NaHO. Acid solutions, or those containing salts of ammonia, are not precipitated.

4. KCN produces a light brown precipitate of Co (CN)2, soluble in excess of the reagent by formation of 2KCN, Co(CN)2. This solution is re-precipitated by the addition of HCl or H2SO4. (If the cobalt solution to which KCN is added be acid, a precipitate is produced, soluble in excess of the reagent. When this solution is boiled, potassium cobalti-cyanide K,Co(CN)6 is formed which is not re-precipitated by HCl or H2SO4 nor by NaClO.)

5. KNO2, added to cobalt solutions with addition of acetic acid, produces on standing in a warm place a yellow crystalline precipitate (double nitrite of potassium and cobalt).

6. Fused with borax in either blow-pipe flame, yields deep blue beads, which are almost black if the quantity of Co be large. (See also 59.)

80. ZINC. Zn, c.w. 65°2.

1. (NH4)2S produces a white precipitate of ZnS, insoluble in excess of the reagent and in KHO, but soluble in the mineral acids.

2. KHO or NaHO produces a white precipitate of Zn(HO), soluble in excess of either reagent and in (NH)HO. This solution is re-precipitated by diluting and boiling, but is not precipitated by addition of NH4Cl.

3. Na2CO3 produces a white precipitate of basic carbonate, insoluble in excess of the reagent.

4. (NH4)2CO3 also precipitates the basic carbonate, but it is soluble in excess of the reagent.

5. Heated on charcoal with Na2CO3 in the reducing blow-pipe flame, a yellow incrustation of ZnO is obtained, which becomes white when cold.

6. Heated on charcoal by the blow-pipe flame after moistening with CoCl solution, an infusible green mass is obtained. (See also 59.)

81. ALUMINIUM. Al, c.w. 27'4.

1. (NH4)2S produces a white flocculent precipitate of Ala(HO)

2. KHO or NaHO produces also a precipitate of Al2(HO), soluble in acids, even in hot acetic acid and in excess of the reagent. This solution is not precipitated by H2S, but is re-precipitated by NH4Cl, or by adding (NH)HO after acidifying with HCl.

3. (NH)HO also precipitates Al2(HO), soluble in a very large excess of the reagent, more difficultly soluble in presence of salts of ammonia.

4. BaCO, produces a precipitate of Al,(HO), mixed

with basic salt.

5. Na,HPO4 precipitates aluminium phosphate, insoluble in (NH4)HO and in NH4Cl, but soluble in KHO or NaHO, and in acids. It does not, however, dissolve in hot acetic acid like aluminium hydrate.

6. Heated on charcoal in the blow-pipe flame, then moistened with CoCl2, and re-heated, an infusible blue mass is obtained.

82. MANGANESE. Mn, c.w. 55.

1. (NH4)2S produces a flesh-coloured precipitate of MnS, soluble in acids, even in acetic acid.

2. KHO or NaHO produces a dirty-white precipitate of Mn(HO)2, insoluble in excess of the reagent; the precipitate rapidly darkens in colour by absorption of oxygen. The freshly-precipitated hydrate is dissolved by NH4Cl, but the higher oxide is insoluble.

3. (NH1)HO produces the same precipitate of Mn(HO), insoluble in excess of the reagent; but it gives no precipitate if the manganese solution contain NHCl. Such a solution on standing precipitates the dark brown hydrate.

4. NaCO3 produces a white precipitate of MnCO3, which darkens in colour by absorption of oxygen.

5. If any manganese solution (free from chlorine) be treated with PbO, and then boiled with HNO3, it is converted into permanganate, which is recognized by its pink colour as soon as the mixture has settled.

6. If any manganese compound be fused on platinum foil with Na2CO3 and a trace of KNO, it is converted into Na,MnO4, recognized by its bright green colour.

7. Fused with borax in the oxidizing flame, an amethyst-coloured bead is obtained, which becomes colourless in the reducing flame.

83. CHROMIUM. Cr, c.w. 52°2.

1. (NH4)2S produces a bluish green precipitate of Cr2(HO), insoluble in excess of the reagent.

2. (NH)HO also precipitates the hydrate, soluble to some extent in excess, yielding a pink fluid, but on heating the precipitation is complete.

3. KHO or NaHO precipitates also Cr2(HO), soluble however in excess, yielding a green or bluish violet solution. On continued boiling or addition of NH4Cl and heating, the hydrate is re-precipitated.

4. BaCO3 produces a precipitate of Cr2(HO), along with basic salt; the precipitation is not complete till the mixture has stood some time.

5. Fused with Na2CO, and KNO, on platinum foil, yellow Na,CrO, is obtained.

6. Fused with borax in either flame (but best in the reducing flame), green beads are obtained.