The Benzoic acid is widely used in the pharmaceutical industry, plasticizers and food preservative which show low aqueous solubility and dissolution rate. The investigation has been made to improve the solubility of benzoic acid by using co-solvent. The co-solvent solution is prepared by using glycerol in water by volume ratio. The result shows the relation between solubility in different co-solvent and temperature whereby as the percentage of glycerol increase, the solubility of benzoic acid increase. A similartrend was depicted in term of solubility relation with temperature as the temperature increase amount of benzoic acid dissolved also increase. Thermodynamics dissociation constant, pKa are directly proportional totemperature between 30oC and 90oC. Enthalpy and entropy change of the dissociation process are 2.907 kJ/mole and -24.09 J/mole respectively. Gibbs free energy of dissociation at 30oC, 60oC and 90oC are -4.390 KJ/mole, -5.114 KJ/mole and 5.837 KJ/mole respectively depicted that the solubility increased with temperature. © 2016 The Authors.