Solubility of (+)-Usnic Acid in Water, Ethanol, Acetone, Ethyl Acetate and n -Hexane

Using ultraviolet spectrophotometry, the solubility of (+)-usnic acid in water, ethanol, acetone, ethyl acetate and n-hexane were measured at temperatures from (278.15 to 338.15) K at atmospheric pressure. The results obtained led to the solubility order: ethyl acetate > acetone > n-hexane > ethanol > water. The solubility values were correlated with the Apelblat equation, the λh equation and the ideal model. The results showed that these three models agreed well with the experimental data.