Determination of the Diffusion Coefficient of Vapors by Means of a Microbalance
Determination of the diffusion coefficient of vapors in gases by Stefan’s method leads to results of rather low reliability. Improvement can be attained by using a recording microbalance. The determination is performed by recording the loss of weight of a small bucket containing a liquid evaporating through a narrow vertical tube. The suspension wire is placed in the axis of the tube. In the case of very narrow tubes (Ø < 10−3 m), tube and container are weighed as a whole.
Variations in apparent weight may occur due to variations in the room temperature and to electrical charges. Small variations in temperature of the evaporating liquid have a very strong influence, especially at higher evaporation rates.
The diffusion coefficient of water vapor in air is determined at 323, 333, and 343 K.
KeywordsDiffusion Coefficient High Evaporation Rate Apparent Weight Evaporation Space Suspension Wire
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