Abstract: A new experimental method for solubility determination was developed based upon optical and chemical principles. It makes the determination of solubility data more objective and accurate. With the aid of laser, the novel method will be much helpful in getting solid-liquid equilibrium data especially for slight solubility, which is always appearing, in environment issue. It can be widely used not only for traditional chemical engineering research but also for the field of environment-chemical engineering research, which is a boom cross-discipline, especially applicable for water solubility determination. Using this method, solubility data for the binary systems of terephthalic acid＋water and terephthalic acid＋acetic acid have been measured in a temperature range of 300 to 445 K and all the experimental data have been correlated by Wilson equation and Wilson-T equation. It indicats that Wilson-T model will be better than Wilson model.

Key words: Slight solubility, Laser, Determination method