The indium activity in liquid In-Sb solutions is measured in the following high temperature solid-state galvanic cellsThe measurements indicate a moderate negative deviation from ideal solution behavior and are in close agreement with previous studies. The results are compared with the available calorimetric and phase-diagram determinations and are found to be consistent with them. An expression for the standard Gibbs energy of formation of solid InSb is presented that is consistent with the direct EMF measurements, calorimetric studies, reported phase diagram, and results of this study. The nonrandom two-liquid theory is found to adequately represent the liquid mixture thermodynamic data.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 141.211.4.224 Downloaded on 2015-06-21 to IP Vol. 131, No. 12 In-Sb LIQUID ALLOYS ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 141.211.4.224 Downloaded on 2015-06-21 to IP