Oscillation enhanced axial transport was experimented through flow visualization techique. We visualized $CO_2$ concentration in rectangular cross-section ducts. Schlieren interferometer was used to get instanteneous one dimensional quantitative $CO_2$ concentration along the duct axis. The effects of frequency and volumetric displacement of pulsation in binary diffusion between $CO_2$ and air was examined quantitatively. This experiment was conducted to know the characteristics of heat loss in pulse tube refrigerator which is very provable for future refrigerator in many aspects. The similarity between heat and mass transfer makes it possible to know heat transfer characteristics by investigating mass transfer phenomena.