', and Related Thermodynamic Functions from 0 to 50°b

Electromotive-force measurements of cells without transference have been used to determine the thermodynamic dissociation constqnts of acetic acid and protonated T r i e ( h y d r o x y m e t h y 1 ) a m i n o m e t h a n e (Tris-H ) i n the mixed solvent 80 mass X 2-methoxyethanoll20 mass X vater from 1 0 to 50°C. Hydrogen g a s electrodes and silver-silver chloride electrodes vere used. Thermodynamic constants for the dissociation process vere derived. The enthalpy of dissociation of Tri8.H' was also determined by titration calorimetry and found to be in acceptable agreement with the value obtained from the emf measurements. Allowance for association of the i o n s of the salts used altered the calculated pK values by sbout 0.03 unit (acetic acid) and 0.06 unit (Tri8.H').