Standard Potentials of Silver-Silver Bromide Electrode in Propylene Glycol-Water Mixtures at Different Temperatures and the Related Thermodynamic Quantities

Standard electrode potentials of the silver-silver bromide electrode were determined In the temperature range 15-45 °C In 20-90 wt % propylene glycol-water mixtures by emf measurements of the cell Pt,H2(g, 1 atm)/HBr(m),propylene glycol (x)-water (y)/AgBr-Ag. The standard molal potential, JE m, In the various solvent mixtures has been expressed as a function of temperature. The primary medium effect, the mean molal activity coefficient, and the various thermodynamic parameters for the transfer of the HBr from water to these solvent mixtures at 25 °C have been reported. The variation of the thermodynamic parameters with solvent composition has been discussed. The number of water molecules coordinated to HBr, n, was calculated from the slope of the linear plot observed between ΔG1,0c and -RT In ϕw (ϕw = volume fraction of water). © 1983, American Chemical Society. All rights reserved.