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Experimental solubility data of sodium naphthalene-1,5-disulfonate in five neat solvents (water, methanol, ethanol, 2-propanol, acetone) and three binary solvent systems (water + ethanol, water + 2-propanol, water + acetone) at different temperatures from 283.15 to 323.15 K were determined by the gravimetric method. The experimental results showed that three kinds of polymorphs appeared in the investigated solvent systems, and the solubility of sodium naphthalene-1,5-disulfonate all increased with increasing temperature and water content. According to the data measured, water was suitable to be the positive solvent, while methanol was considered to be a less-effective antisolvent due to its relatively large dissolving capacity. By means of our research, the solubility of sodium naphthalene-1,5-disulfonate in the neat solvents had a relation with the polarity of the solvents. The solubilities of sodium naphthalene-1,5-disulfonate were fitted by the modified Apelblat, Jouyban-Acree, van’t Hoff-Jouyban-Acree, and Apelblat-Jouyban-Acree models. The results showed that the four models can predict the experimental values very well.

The solubility of l-alanine in five binary systems water + methanol, water + ethanol, water + 1-propanol, water + 2-propanol, and water + acetone and 12 neat solvents (water, 1-butanol, methanol, 2-butanol, 2-methyl-1-propanol, 1-pentanol, 1-propanol, ethanol, 2-propanol, ethyl acetate, acetonitrile, and acetone) was determined by the gravimetrical method within the temperature range from 283.15 to 323.15 K under atmospheric pressure. The experimental results indicated that the solubility increased with increasing temperature and mole ratio of water in all investigated solvents and decreased with the rise of the mole fraction of five different organic solvents in the binary solvent systems. The order of l-alanine solubility in the selected pure solvents was water > 1-butanol > methanol ≈ 2-butanol > 2-methyl-1-propanol ≈ 1-pentanol ≈ 1-propanol ≈ ethanol > 2-propanol > ethyl acetate > acetonitrile > acetone. The solubility was mathematically represented by the modified Apelblat, Jouyban–Acree, and Apelblat–Jouyban–Acree models. All the models can be found to agree well with the data in the experiment.

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