Studies on Phase Equilibria in the Systems CdCl_2-PrCl_3-HCl(8.3 %)-H_2O and CdCl_2-PrCl_3-H_2O at 298 +-1 K

摘要

The equilibrium solubility of the quaternary system CdCl_2-PrCl_3-HCl(8.3 mass %)-H_2O and the ternary system CdCl_2-PrCl_3-H_2O at 298 K was investigated,and the corresponding phase diagrams were plotted.The results showed that the quaternary system was a complicated one consisting of four stable equilibrium solid phases CdCl_2 centre dot H_2O,Cd_8PrCl_(19)centre dot 20H_2O(8:1 type),Cd_4PrCl_(11)centre dot H_2O(4:1 type),and PrCl_3 centre dot 7H_2O,of which two new compounds Cd_8rCl_(19)centre dot 20H_2O and Cd_4PrCl_(11)centre dot H_2O were found to be congruently soluble in the system.The ternary system coPnsisted of four stable equilibrium solid phases(CdCl_2 centre dot 2.5H_2O,CdCl_2 centre dot H_2O,Cd_4PrCl_(11)centre dot H_2O,and PrCl_3 centre dot 7H_2O)and a metastable phase(Cd_8PrCl_(19)centre dot 20H_2O).Two new compounds of the 8:1 type and 4:1 type were found to be incongruently soluble in the system.Both of the 8:1 type and 4:1 type compounds obtained were identified and characterized by the method of X-ray diffraction and the thermal analysis methods of thermogravimetry-differential thermogravimetry(TG-DTG).