Estimate the diffusion coefficient of carbon tetrachloride into air from the following data recorded in a Stefan-tube experiment with carbon tetrachloride ad oxygen: diameter of tube and its length above liquid surface: 1 cm and 15 cm respectively; temperature and pressure maintained: 0°C and 760 mm of mercury; evaporation of carbon tetrachloride: 0.03 gm in 10 Hr; vapour pressure of carbon tetrachloride: 33 mm of mercury.