Aq. solns. of formic acid were exptl. investigated in a modified sweeping gas membrane distn. (SGMD) configuration. A thermostated sweeping gas was used in order to enhance the mass transfer performance. A new tubular module was designed and built for this purpose. The effects of the relevant process parameters on the permeate flux and selectivity were studied. Expts. with pure water and pure formic acid were used to est. certain parameters in the model. From these mass transfer coeffs., the fluxes and selectivity for aq. formic acid mixts. were calcd. using the math. model previously described. The model predictions were compared with the exptl. data and a good agreement between both flux values were obtained. [on SciFinder (R)]