Evaporation Rate Measurement of Water and Liquid 1-Alkanols across Air-Liquid Interface Using Thermogravimetry

Evaporation rate measurements of water across air/water interface were made by using a thermogravimetry technique. A sample liquid was held in a partially filled, open-topped pan in a furnace tube, through which dry air was flowing. The effect of the flow rate of the dry air on the evaporation rate was very large at lower flow rates, while it became smaller at higher flow rates. The evaporation rate of water over the temperature range 298.2-333.2 K was studied in order to obtain the activation energy for the evaporation. The energy was found to decrease with increasing temperature. A newly developed equation was used to analyze the evaporation rate. Purified liquid 1-alkanols (carbon number = 4, 6, 8, 10, and 12) were employed as test substances in order to estimate the effects of terminal CH2OH group and of residual CH2 groups on the activation energy. The contribution of -CH2OH group to the activation energy was found to slightly decrease with increasing temperature, while the contribution of residual CH2 group increased with increasing chain length; the temperature-dependence remained almost the same irrespective of the alkyl chain.