The purpose of the series of papers is to predicted the rate of absorption or desorption of a gas in an agitated liquid. The results will be reported in several parts. Part 1 deals with techniques devised to measure the interfacial areas and bubble sizes, and correlations are given for these quantities in terms of the power dissipated by the agitator, the gas flowrate to the equipment and the physical properties of the system including the effect of solutes inaerated aqueous solutions. A correlation is given for the particle size in both gas-liquid and liquid-liquid dispersions and a short section deals with the problem of predicting the power consumption of agitators workingin aerated and in non-Newtonian fluids. Part 2 will report mass-transfer coefficients for gas-liquid contacting in agitated vessels as well as other types of contacting devices. It is planned to use the results of the above p[apers, in a subsequent publication, to prepare design and operating recommendations for fermentation equipment.