New approach to diagnostics of organic impurities in water

The thermocapillary convection (TC) induced by a laser beam on thin aqueous layers placed on an absorbing non-heat-conducting substrate is experimentally investigated. It is shown that after a lag time after turning on of a laser beam the presence of TC is registered by a sharp splash, after which the TC response grows to its steady-state value. The deviation of the duration of this pause from its quadratic variation with thickness of the liquid layer depending on the degree of organic impurity of water is another important experimental result. The above results can serve as a basis for development of a method for measuring the thermal diffusivity of liquids and for monitoring water purity. (C) 2004 Elsevier B.V. All rights reserved.