The determination of the second dissociation constant of carbonic acid in 15 mass% glucose-water mixed solvent, K-2, has been made on cell of the type : Pt, H-2 (101.325 kPa) \Na2CO3 (m(1)), NaHCO3 (m(2)), NaCl (m(3)), 15 mass% glucose+water\ AgCl-Ag at 278.15-318.15 K. The dependence of pk on temperature has been obtained, that is, pK(2)=-52.01+/-9561.2/ T + 9.955 x 10(-2)T. The maximum value of K-2 in the mixed solvent is found to occur at 310.0 K and the Value of pK(2) is 9.683 at this temperature. However, the maximum value of K-2 in pure water occurs at 349.3 K and pK(2) (W)=10.121. It is evident that BCO3- species increases in acidic strength and that the temperature occurred maximum value of K-2 decreases when glucose is added to a solvent that is initially pure water.