Solubility of Tetrahydroxybenzophenone (THBP) in Acetone

Solubilities of nonsolvate and acetone-solvate crystals of tetrahydroxybenzophenone (THBP), a raw material of photoresists, in acetone were measured at temperatures ranging from 283.15 K to 323.15 K and from 288.15 K to 318.15 K, respectively. The solubility of nonsolvate (needle crystal) was higher than that of acetone-solvate (granular crystal) at temperatures lower than 314.85 K, while at temperatures higher than 314.85 K it was lower than that of the granular crystals. The molar ratio of solvated acetone to THBP in the granular crystal was determined to be 1:1 by thermogravimetry and by gas chromatography. The powdery crystals of acetone-solvate THBP were unstable in the air at room temperature and lost acetone gradually during a few hours. Dry powder was obtained by vacuum drying. The solubility of the dry powder was the same as that of the “wet” granular crystals. This suggests that the dry powder returned to the original acetone-solvate when dispersed in acetone solvent.