An intense nanosecond pulse of light is used to create electron-hole pairs in small CdS crystallites (containing ca. 10$^2$ atoms) suspended in a liquid. Electronic processes within the crystallite are monitored by measuring the changes of oxidation state of a redox indicator partitioned between the crystallite surface and the bulk liquid. The observed time course of these changes is analysed by the method of competition kinetics, and numerical values of key microscopic parameters (recombination rate constant, trap concentration and depth, interfacial electron transfer rate constant, etc.) are determined. An unexpected result is that the trapping cross section for the shallow electron traps is much greater than in bulk CdS.