Notes on qualitative analysis : concise and explanatory / by H.J.H. Fenton.

  • Fenton, Henry John Horstman, 1854-1929.
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: Notes on qualitative analysis : concise and explanatory / by H.J.H. Fenton. Source: Wellcome Collection.

    16/108 (page 4)
    Mercuric Salts. Solutions of mercuric salts (e.g. HgCl2) give with Hydrosulphuric acid, black ppt. of mercuric sulphide, HgCl2 + H2S = HgS + 2HC1. This ppt. is insoluble in ammonium sulphide and in dilute HN03. Strong HN03 converts it into a white mixture of 2HgS and Hg(N03)2. Caustic potash, yellow ppt. of mercuric oxide, HgCla + 2KHO = HgO + 2KC1 + H20. Potassium iodide, red ppt. of mercuric iodide Hgl2, soluble in excess, forming the double iodide (Hgl2.2Kl). Ammonia, white ppt. of mercuric-ammonium chloride (NHgH2)Cl. Stannous chloride, first a white ppt. of mercurous chloride, which is afterwards further reduced to metallic mercury, if sufficient SnCl2 is present. COPPER. Cupric Salts (usually green or blue). Solutions of cupric salts (e.g. CuS04) give with Hydrosulphuric acid, black ppt. of cupric sulphide, CuSO. + HS = CuS + H SO,. 4 2 2 4 This ppt. is nearly insoluble in ammonium sulphide. Soluble in hot dilute HN03, forming cupric nitrate Cu(N03)o. Insoluble in dilute H2S04. [The precipitation by H2S is prevented by the presence of potassium cyanide owing to the formation of a double cyanide Cu2Cy8. 2KCy.] Potassium ferrocyanide, chocolate ppt. of cupric ferrocyanide, 2CuS04 4- K4(FeCy6) = Cu2(FeCy8) + 2K2S04. Ammonia, pale greenish-blue ppt. of a basic cupric sulphate (such as CuS04. 2Cu(OH)2), readily soluble in excess of NHa, forming a dark blue solution. This solu- tion contains a compound having the composition (CuS04 + 4NH3 + H20) or {(N2H„Cu)0 + (NH()sSOJ. Caustic potash, pale blue ppt. of cupric hydroxide Cu(OH)2, which turns black on boiling, CuO being formed. Potassium iodide, dirty white ppt. of cuprous iodide Cu2l2, free iodine being liberated. Potassium cyanide, brownish-yellow or olive-green ppt. of cupric cyanide CuCy2, which rapidly loses cyanogen, becoming (2CuCy2 . Cu'2Cy2) or Cu'2Cy2. These cyanides dissolve in excess of KCy, forming double cyanides CuCy2 . 2KCy and Cu2Cy2. 2KCy respectively. Many reducing agents such as glucose, aldehyde, &c. in presence of caustic potash, precipitate red cuprous oxide Cu20, on heating.