Charge on mercurous ion

To determine the atomicity of the mercurous ion in aqueous solution by measurements of e.m.f. 

If the atomicity of the ion is x, its charge will be x units, and the process occurring when one faraday of electricity flows through the cell from left to right will be 

Additional evidence confirming that the mercurous ion is HgJ is discussed by Sidgwick ( The chemical elements and their compounds , Oxford, 1950, volume 1, p. 289). Higginson (J. Chem. Soc. 1951,1438) has reported that spectrophotometric measurements on very dilute solutions ( 10 mole H) indicate some dissociation of the ion HgJ to 2Hg+. 

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