The interaction of gelatin with various metal ions was investigated by electrophoresis, viscosity measurement and pH titration.
Effect of metal ion on the electrophoretic mobility of the gelatin-AgBr sol was measured at pH 6 with several added metal ions. The mobility was decreased with the increase of metal ion concentration ae a consequence of the metal ion binding to gelatin adorbed around AgBr particles. Assuming that the reciprocal of the concentration of the metal ion at which the mobility of the sol becomes zero represents the binding affinity, it was found that the sequence of the binding affinity was Cu⁺²>Zn⁺²> Co^-2, Ni⁺², Mn⁺²>Ca⁺². The result was supported by the measurement of viscosity variation and pH titration curve of gelatin containing a metal ion.
Electrophoresis of the gelatin-AgBr sol cotaining K₂SO₄ or any one of following complexes (K₂PtC1₄ and Na₂WO₄) at pH 3.7 was also measured. It was found that WO₄^-2 was bound by gelatin while the others were not.