Effect of hydrotropes on solubility and mass transfer coefficient of methyl salicylate

This paper presents a comprehensive study on the effect of citric acid, sod ium benzoate, sodium salicylate, and urea (hydrotropes) on the solubility a nd mass transfer coefficient for the extraction of methyl salicylate in wat er. A Minimum Hydrotropic Concentration (MHC) in the range between 0.20 and 0.90 mol/L was found essential to show a significant increase in the solub ility and mass transfer coefficient for the methyl salicylate-water system. The solubility of methyl salicylate has been increased to a maximum value of 22.84 in the presence of citric acid as hydrotrope at concentration of 2 .00 mol/L and temperature of 333 K. The maximum enhancement factor for the mass transfer coefficient was found to be 7.88 in the presence of citric ac id as hydrotrope at a concentration of 2.00 mol/L at 303 K at 600 rpm. The Setschenow constant, K,, a measure of the effectiveness of the hydrotrope, has been determined for each case, and the highest value has been observed as 0.743 in the case of citric acid.