AbstractMass transfer coefficients for the solution, without reaction, of oxygen in cyclohexane over a wide range of temperature and pressure have been measured in a flat interface reactor (FIR) and a gas sparged stirred‐tank reactor (STR). Solubilities have also been measured and it is suggested that a modified Henry's law coefficient of 1.09 × 10−2kmol/m3· bar can be regarded as constant over the temperature range 293–435 K. The physical mass transfer coefficient in the STR shows very little variation over this temperature range and a value of 3.5 × 10−4m/s can be assumed for 423–435 K. However, coefficients in the FIR increase with agitation rate as expected. The difference is ascribed to interference by neighboring bubbles in the transfer process, when diffusivities are high, and also to the lowering of surface tension at high temperatures. A model proposed by Gal‐Or and Resnick is reviewed in its application to the