We have studied the coalescence of bubbles in electrolyte solutions by measuring the fraction of contacting bubble pairs that coalesce as a function of electrolyte concentration. At low concentrations, we have reproduced earlier results in the literature, but by extending our measurements to higher electrolyte concentrations, we have found that some electrolytes previously thought not to inhibit bubble coalescence do show a transition to coalescence inhibition at higher (>1 M) concentrations. These results suggest that coalescence inhibition should be studied over wider concentration ranges if full insight into the factors governing coalescence inhibition is to be obtained.