Workman-Reynolds freezing potentials have been measured for the first time across the interface between single crystals of ice 1h and dilute electrolyte solutions. The measured electric potential is a strictly nonequilibrium phenomenon and a function of the concentration of salt, freezing rate, orientation of the ice crystal, and time. When all these factors are controlled, the voltage is reproducible to the extent expected with ice growth experiments. Zero voltage is obtained with no growth or melting. For rapidly grown ice I h basal plane in contact with a solution of 10(-4) M NaCl the maximum voltage exceeds 30 V and decreases to zero at. both high and low salt concentrations. These single-crystal experiments explain much of the data captured on this remarkable phenomenon since 1948.