An electrochemical cell is described for measuring electrode reaction kinetics at low and variable temperatures in nonaqueous solvents. The cell contains a working electrode of conventional size (at which the standard heterogeneous electron transfer rate constant is determined by cyclic voltammetry) and a microelectrode (at which the diffusion coefficient is measured by steady-state microelectrode voltammetry). I Jncompensated solution resistance is minimized by a combination o f close placement o f the reference electrode salt bridge tip and the working electrode surface and instrumental positive feeclback. Cell performance is evaluated by an examination o f ferrocene oxidation and manganese( 111) (tetra~~henylporpliyrin ) chloride reduction at temperatures between 229 and 298 K. Comparison of the rcsponses from these reversible and quasi-reversible redox couples in the sane solution demonstrates that the effects of uncompensated solution resistance are absent from the experimental measurements and that increases in the cyclic voltammetric peak potential separation with sweep rate are due entirely to the kinetics o f the Mn(IlI)/Mn( 11) electrode reaction.1040-0397/90/$3 50 + .L5