The propanoic acid 3-(hydroxyphenylphosphinyl)-monosodium salt (HPPS) and disodium salt (SHPPS) particles as most important flame retardants were synthesized by 3-(hydroxyphenylphosphinyl)propanoic acid with sodium hydrogen carbonate at room-temperature and characterized. The solubility of HPPS and SHPPS in pure water, methanol, ethanol, acetone, acetic acid and ethyl acetate were measured over a temperature range from 293.15 to 343.15 K under atmospheric pressure. Furthermore, the solubility of HPPS in mixed waters (ethanol + water) was determined and found to exhibit a synergistic effect. The two models, including the modified Apelblat model and the Scatchard-Hildebrand model were applied to correlate the experimental solubility data. The calculated solubilities are in good agreement with the experimental results. (C) 2013 Elsevier B.V. All rights reserved.