Comments Concerning “Equilibrium Phase Diagram of the Ternary 2-Nitrobenzoic Acid + 3-Nitrobenzoic Acid + Acetone System at 283.15 and 313.15 K”

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In a recent paper published in this journal Zhao et al. reported the equilibria phase diagram of the ternary 2-nitrobenzoic acid (1) + 3-nitrobenzoic acid (3) + acetone (3) system at both 283.15 and 313.15 K. Schreinemaker’s wet residue method was used to determine the concentrations of the liquid and solid phases. The experimental methodology involved filtering the wet solid residue from an equilibrated saturated solution (the authors state aqueous solution, which I believe should read acetone solution) and then analyzing the collected liquid and solid phases by high-performance liquid chromatography. The authors reported the concentrations as mass% for the ‘‘wet’’ solid phase. The purpose of the present communication is to point to errors that go undetected when experimental data is reported on the ‘‘wet’’ solid phase basis. In Tables 1 and 2, I have reproduced the authors’ experimental solubility data for the ternary 2-nitrobenzoic acid (1) + 3-nitrobenzoic acid (2) + acetone (3) system measured at 283.15 and at 313.15 K. For the third experimental data point in Table 1, the composition of the ‘‘wet’’ solid phase is reported to be 2.55 mass% of 2-nitrobenzoic acid and 70.39 mass% of 3-nitrobenzoic acid, respectively. The remaining 27.06 mass% would be acetone that would have been adsorbed onto the filtered solid residue from the saturated solution. The solid residue was analyzed ‘‘wet,’’ and the chromatographically measured concentrations would include the amounts of 2-nitrobenzoic acid and 3-nitrobenzoic acid absorbed onto the solid residue along with acetone. Through mass balance concentrations, it is possible to subtract the amount of 2-nitrobenzoic acid and 3-nitrobenzoic that would have been absorbed onto the solid residue along with the 27.06 mass% of acetone. For mathematical convenience, I have assumed 100 g total of each phase, so that the mass percentages become the mass of each chemical.