Qualitative analysis / by William Briggs and R.W. Stewart.

  • William Briggs
Date:
1913
Catalogue details

Licence: Public Domain Mark

Credit: Qualitative analysis / by William Briggs and R.W. Stewart. Source: Wellcome Collection.

    61/180 page 45
    MANGANESE, Mn. Solution—Manganous Sulphate, MnS04. 1. Ammonium sulphide, (NH4)2S, gives a flesh-coloured precipitate of manganese sulphide, MnS. [Distinction from Ni, Co, and Zn.] MnS04 + (NH4)2S = MnS + (NH4)2S04. The precipitate is readily soluble in dilute mineral acids, and is even soluble in acetic acid. [Distinction from Ni, Co, and Zn.] MnS + 2 HC2H302 = H2S + Mn(C2H302)2. 2. Sodium hydroxide, NaOH, or potassium hydroxide, KOH, gives a white precipitate of manganous hydrate, Mn(OH)2, insoluble in excess. The precipitate speedily absorbs oxygen from the air, and turns dark brown with the formation of the hydrated manganic oxide, Mn203, H20, which is insoluble in NH4C1. 2 NaOH + MnS04 = Mn(OH)2 + Na2S04. 4 Mn(OH)2 + 02 = 2 Mn203, H20 + 2 H20. 3. Ammonium hydroxide, NH4OH, produces the same precipitate, except when ammonium salts aro present, when the precipitation is prevented. [On adding NH4C1 and NH4OH to a solution of a manganese salt, a soluble double chloride of ammonium and manganese, 2 NH4C1, MnCl2, is formed. On exposure to air, this solution is gradually oxidized, and the manganese precipitated as Mn203, H20. For this reason manganese may be precipitated in Group III., but the precipitation does not take place until after exposure to the air for some time. Ferric hydroxide is precipitated immediately.] 4. Fuse a very small quantity of a manganese salt with fusion mixture and a little potassium nitrate, KN03, on a piece of platinum-foil. A deep green mass remains. This
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