Ionization constants for deuterium oxide in deuterium oxide-organic mixtures

A potentiometric method using a glass electrode has been applied to determination of ionization constants for deuterium oxide (D₂O) in binary mixtures of D₂O with dioxane, tetrahydrofuran, acetone, dimethylsulfoxide, CH₃CH₂OD, and CH₃OD at 25°C. The results are compared with values of ionization constants for H₂O obtained previously in the corresponding H₂O-organic mixtures, and the isotope effect is shown to be small. Further calculations with the D₂O results show that the first five solvents mentioned above are neither appreciably acidic nor basic in D₂O solution, but that CH₃OD shows slightly acidic behavior (pK_a=16.0±0.3).