摘要：

Excess enthalpies of six binary mixtures of CH 3 OD+CH 3 OH, CH 3 OD+CD 3 OD, CD 3 OD+CH 3 OH, C 2 D 5 OD+C 2 H 5 OH, C 2 D 5 OD+C 2 H 5 OD, C 2 H 5 OD+C 2 H 5 OH have been determined over the whole range of mole fractions at 298.15 K in order to know the isotopic effect on hydrogen-bonding accurately, although there are many reports on the differences in the strength of hydrogen-bonding between OH and OD.All excess enthalpies measured are very small and endothermic. The mixtures of CH 3 OD+ CH 3 OH, and C 2 D 5 OD+C 2 H 5 OH showed the largest excess enthalpies among each methanol and ethanol mixtures. The difference of intermolecular interaction between OH and OD in methanol and ethanol was almost same value of (1.82±0.04) J mol -1Excess enthalpies of 1,4-dimethylbenzene+1,3-dimethylbenzene and 1,4-dimethylbenzene+1,2-methylbenzene were measured by three different principle calorimeters at 298.15 K in order to know the precision of calorimetry for a small enthalpy change.

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