Solubility of cadmium chloride and the standard potential of the cadmium electrode in formamide
The e.m.f. of the cell, Cd : Hg(2-phase amalgam)/CdCl2(m)/AgCl/Ag, where m is the number of moles of anhydrous CdCl2 per kg of formamide and lies in the range 0 < m < 0.02 has been measured at 298.15 K. The measurements are analyzed in terms of complex formation in solution to yield a value of the molal standard potential of the Cd2+/Cd electrode of –0.412 V at 298.15 K. By combining this value with the standard potential of the Cd/CdCl2(s)/Cl– electrode,1 where CdCl2(s) denotes a solid solvate of composition CdCl2· 2½HCONH2, the solubility product of cadmium chloride in formamide is calculated to be 2 × 10–7(mol kg–1)3. The solubility of anhydrous cadmium chloride in formamide has also been measured at 288.15 K, 298.15 K and 308.15 K using a radiochemical technique. The results suggest extensive complex formation in formamide, the dominant species being the CdCl2–4 ion.