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The equilibrium solubility of 3- and 4-nitrophthalic acids in water was measured experimentally using Schreinemaker's wet residue method at temperatures ranging from (285.15 to 348.15) K at atmospheric pressure. The solubility of 3- and 4-nitrophthalic acids in water increased with the increase of temperature. The experimental solubility is correlated by an empirical equation. The calculated values via the empirical equation agreed well with experimental results for 3- and 4-nitrophthalic acids.

The solubility data of the calcium acetate-magnesium acetate-water system at 298, 313, and 323 K were measured using the SchreinemakerÕs wet residue method, the corresponding phase diagram for the system were constructed. The solid phase in the system at different temperatures was confirmed by the SchreinemakerÕs wet residue method, which correspond to Mg(CH 3 COO) 2 AE4H 2 O and Ca(CH 3 COO) 2 AE2H 2 O. At the studied temperature, no double salt was formed. The crystalline region of Ca(CH 3 COO) 2 AE2H 2 O is larger than that of Mg(CH 3 COO) 2 AE4H 2 O. The solubility of Mg(CH 3 COO) 2 increases with the increasing of the temperature, while the solubility of Ca(CH 3 COO) 2 decreases with the increasing of the temperature.

The solubility and density of the equilibrium liquid phase for the ternary K2C2O4 + H2O2 + H2O system were determined experimentally at (283.15 and 293.15) K. The phase diagrams of the system were constructed based on the measured solubility. The compound K2C2O4·H2O2 was confirmed by Schreinemaker's wet residues method. At (283.15 and 293.15) K, two solid phases were formed in the ternary K2C2O4 + H2O2 + H2O system that correspond to K2C2O4·H2O and K2C2O4·H2O2. Results indicated that the phase diagrams of the ternary system are similar at different temperatures. The double salt K2C2O4·H2O2 has a bigger crystallization field than either K2C2O4·H2O or the mixture. The solubilities of K2C2O4·H2O and K2C2O4·H2O2 increase slightly with increasing temperature, while the crystalline region of the compound K2C2O4·H2O2 decreases as the temperature increases.

Solubility data for the Na2CO3 + Na2SO4 + H2O2 + H2O system at 293 K were determined by Schreinmaker's method. The results were used to construct a phase diagram in the oblique projection according to the Jãneck method. At constant temperature, when the hydrogen peroxide concentration is below 50 % (mass fraction), this diagram includes three invariant points, six double saturated liquid curves, and four crystallization fields corresponding to Na2CO3·10H2O, Na2SO4·10H2O, Na2CO3·1.5H2O2·H2O, and Na2SO4·0.5H2O2·H2O.