Phase equilibria of Cr(NO3)3–Met–H2O system with synthesis and characterization of solid complexes

The solubility property of the ternary complex Cr(NO3)3–methionine (Met)–H2O has been investigated in the whole concentration range by phase equilibrium method, and the phase diagram has been constructed. It was indicated that the new complexes of Cr(Met)(NO3)3·2H2O (D) and Cr(Met)2(NO3)3·2H2O (E) exist in the system of Cr(NO3)3–Met–H2O. These complexes that are congruently in water have not been reported in literature. Under the guidance of the phase diagram, the two complexes have been prepared and characterized by chemical analysis, elemental analysis, IR and TG–DTG. Their combustion energies have been determined by a RBC-type I rotating-bomb calorimeter, and their standard enthalpies of formation, ΔfHm°, have been calculated which are −1842.01±2.13 and −1136.16±4.45 kJ mol−1, respectively.