The electrical conductance and UV absorbance of 4,N-dimethyl Pridinium Iodide (NDMPI) were measured in the ethanol volume percentage, 95, 90, 80 and 60 of an ethanol-water mixture at 15, 25, 35 and $45^{circ}C$. Ionic association constants(K) of NDMPI were evaluated in accordance with a combined method of conductance UV absorbance. The ion size parameter (${gamma}_{pm}$) and dipole momemt (${mu}_{A+D-}$) of NDMPI were obtained from the values of K and dielectric constant. The ${mu}_{A+D-}$- values were in good agreement with the values of transition moment(${mu}_{mn}$) which is calculated form the UV peak values. The large negative values of the electrical enthalpy (${Delta}H_{el}^{circ}$) and entropy (${Delta}H_{el}^{circ}$ ) have proved that NDMPI had a positive hydration. The positive values of entropy (${Delta}S^{circ}$) means the formation of NDMPI ion goes with dehydration.