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The enthalpy changes. entropy changes and equilibrium constants of coordination rcactious of 18-crown-6 with the alkali ions Na+ and K+ at 298.15K were measured hy using RD-496 microcalorimeter with methanol, ethanol, n-propanol and n-butanol as solvcnts respcc-tively. The results indicated that the enthalpy changcs Hm, entropy changes Sm, and the stability of the complexes are closely related with the polarity of the solvents, and the order of the stability is ethanol>methanol>n-propanol>n-butanol>H2O for the same complex in the solvents investigated. The stability order was reasonably cxplained by relating the stability constitants of the complexes with the dielectric constants of these solvents, and by using the model of solvated-desolvated ions and ion pair in the coordination reactiolis.