The convective gravimetric sorption technique (CGS) formerly known as ambient pressure gravimetric sorption has been developed as a flexible technique for measuring diffusion and solubility in polymer-solvent systems. New features have been added to the apparatus to aid in data collection and the flow system has been largely rebuilt. While most of the data that has been collected with the apparatus is proprietary, diffusion coefficients of toluene in polystyrene were measured and compare well to previous data. A discussion of mass transfer considerations within this experiment is also presented.