Abstract: This paper presents an experimental investigation on the crystallization thermodynamics of cobalamine（vitamin B12）and the metastable zone is measured at different solvent ratios and temperatures by laser. The influence of four typical ionic impurities (Na+，Mg2+，Ca2+andFe3+) on cobalamine crystallization is also studied. As a result，It is clear that Fe3+ and Mg2+ have more significant effect than Na+ and Ca2+ on crystal morphology using dilution crystallization.

Key words: Cobalamine, Dilution crystallization, Ionic impurities