Stripping chronopotentiometric measurements following the mechanical transfer of insoluble solid reactants to the surface of a paraffin impregnated graphite electrode are described. By the new technique, the potentials can be determined at which the heterogeneous redox reactions between the immobilized microcrystals and dissolved oxidants, or reductants occur. The method is tested with lead and tin metal particles and lead(II)oxide and sulfide powders in the oxygen saturated electrolytes of various pH. The oxidation of lead is a fast process, but tin particles are highly passivated in the basic media. A difference between the responses of electrodeposited and mechanically transferred lead is reported.