The solubilities of the ternary systems H3PO4 + CdCl2 + H2O and H3PO4 + MgCl2 + H2O were determined at temperatures ranging from 298.15 to 353.15 K using a specific equilibrium method. The solubility of cadmium chloride decreases as phosphoric acid concentration increases, likely due to the formation of cadmium complexes in concentrated acid. However, magnesium chloride was observed to exhibit extremely high solubility, becoming infinitely soluble in most cases, particularly when phosphoric acid concentrations exceeded those of magnesium. The precipitated solid phases were confirmed using X-ray diffraction analysis. Indeed, the ternary system H3PO4 + CdCl2 + H2O is complex with salts CdCl2 ∙ 2.5H2O(s) formed at 298.15 K, and CdCl2 ∙ H2O(s) at temperatures of 313.15, 333.15, and 353.15 K. In the ternary system H3PO4 + MgCl2 + H2O, for ionic strength fraction y = 0.20 there is one soluble compound corresponding to the solid phase MgCl2 ∙ 6H2O(s) for two temperatures, namely 298.15 and 313.15 K. For other ionic strength fractions (y = 0.50, and 0.80) at all temperatures magnesium chloride was observed to exhibit extremely high solubility, becoming infinitely soluble. The results provide useful data that help to solve problems faced during the phosphoric acid production by wet process.