Summary: The distribution of cobalt between eutectic melts of K-Li-NO3 with varying chloride concentration and suspended grains of γ-Al2O3 at 160° C was measured using Co-60 as tracer. By an iteration method of evaluation, the stability constants were determined for the following complexes: CoCl+: ß1 = 13,0; CoCl2:ß2 = 104; CoCl-3:ß2 = 251.