A Scanning Refractometer for Electrochemical Studies

We describe a system for measuring the refractive index of an electrolyte as a function of distance from an electrode. A modulation technique is used to measure small deflections of a laser beam passing near the electrode. Preliminary re-sults show that the index scanner provides a quantitative r al-time probe of concentration gradients in electrochemical processes. Furthermore, it is simpler to implement than interferometric methods. The rate of an electrochemical reaction is, in part, deter-mined by the concentration f reactants at the electrode and the rate at which they can be replenished. The mass-transfer process is driven by the combined effects of dif-fusion, migration, and convection. The calculation of the flux and concentration of the electroactive species in the proximity of an electrode is a complicated hydrodynamic problem and requires some approximations (1). Thus, a direct measurement of the concentration profile near a working electrode can be very useful in understanding a