It has been found that previous results on selective adsorption of acetylene over ethylene and ethane reported by Yang et al. were influenced to a significant extent by acetone impurities (in acetylene). This work reports corrected adsorption isotherm results with acetone carefully removed on gamma-alumina and monolayer NiCl2/gamma-alumina. For both sorbents, adsorption strengths followed the rank order acetylene > ethylene. The selectivity towards acetylene of NiCl2/gamma-alumina is higher compared to the bare gamma-alumina.