Abstract

R. Abou Shahba, N. S. M. Hassan, A. Salah And L. A. Kamel

The Galvanostatic polarization of nickel amalgams in different concentrations of KSCN solutions have been investigated. It is found that, save for dilute nickel amalgam electrodes in concentrated thiocyanate solutions, the oxidation curves indicated regions for the charging of the anode double layer, dissolution of Ni as Ni++ which in presence of SCN- give Ni(SCN)4— (soluble complex), then three arrests due to the farmation of mercury tetrathiocyanato nickalate (II) Hg (Ni (SCN)4 (blue precipitate), together with mercuric thiocyanate (white precipitate), along arrest I. Mercuric thiocyanate react with excess SCN~ ions to form the potassium tetrathiocyanato mercurate (II), K2 [Hg (SCN)4 yellow precipitate, along the second arrest I. Then niercurous thiocyanate is formed along the third arrest (through reaction of mercuric thiocyanate and the mercury of the amalgam) before the potential rises to O2 evolution values. With dilute nickel amalgams hi concentrated SCN~ solution a new a arrest appeared due to oxidation of SCN~ to SO4 and mcrcurous sulphate is formed along the fourth arrest before the potential rises to O2 evolution values.

Aqueous; Thiocyanate; Galvanostatic

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