To date models used to describe the gas hold-up in a homogeneous bubble flow have not considered the coalescence behaviour of the gas bubbles. in several studies, however, it is shown that coalescence has a strong effect on gas hold-up. Using the results of experimental investigations, a new model was developed to calculate the gas hold-up in different electrolyte solutions. The coalescence in this model is considered as a reaction of two bubbles. The reaction rate constant of the coalescence reaction is the main parameter for predicting the gas hold-vp for different solutions and gases. It not only depends on the type and concentration of the electrolyte, but also on the kind of gas.