Chemical wave driven convection in capillary tubes

Chemical wave driven convection in capillary tubes

Thesis for M.Sc. degree, unpublished, May 1997.

Doyle W. Rose

Department of Physics, University of Toronto, 60 St. George St., Toronto, Ontario, Canada M5S 1A7.

Chemical wave propagation in thin capillary tubes was studied by using the iodate-arsenous acid reaction with a pH indicator. The speed of the reaction front was measured for upwards, downwards, horizontal and inclined front propagation. It is believed that downward propagation gives a front speed which is purely determined by the reaction kinematics. Front speeds greater than this are thought to be assisted by convection. Such greater front speeds were observed for upwards and most inclined propagation. However, fronts propagating horizontally and inclined near the horizontal had front speeds less than the downwards speed. This was unexpected, since theory and previous experiments had shown that the horizontal front speed was greater than the downwards front speed. It is not known if this slow horizontal front speed is a convective effect, or due to some other factor. In addition to the effect of angle, the effect of tube diameter on convection was also studied. Convection for upwards propagation had an onset diameter between 1.90 mm and 2.05 mm. For inclined angles, convection was observed in tubes of all diameters. The front speed increased as the tube diameter was increased, indicating that convection is more vigorous in larger tubes.

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