The adsorption and desorption of the binary system N2xAr1-x confined in the cylindrical 4 nm diameter pores of Vycor glass has been studied using positron annihilation spectroscopy. When the Vycor sample was suspended in the gaseous mixture, the gas-liquid and liquid-gas phase transitions of the confined fluid exhibit hysteresis which varies little with composition, indicating that the confined mixture behaves like a simple fluid. However, if bulk mixture surrounding the samples was allowed to condense, the liquid-gas transition exhibited a much larger degree of hysteresis for the mixtures; although unchanged for either pure gas. The observed behavior indicates that bulk liquid condensed around the Vycor samples is able to interact with the confined fluid, causing the confined mixture to become Ar rich.