Although the existence of a thermal diffusion effect in liquids has been known for more than 100 years, relatively little experimental work was done until the development of the thermogravitational column in 1939-It consisted of parallel hot and cold surfaces mounted vertically so that thermally induced convection currents, upward along the hot surface and downward along the cold surface, provided countercurrent flow. One factor which has made experimental results obtained with thermogravitational col¬umns difficult to interpret is the so-called forgotten effect. The for¬gotten effect refers to the effect on the column performance of that part of the density gradient due solely to the concentration gradient in the liquid. The objective of this work was, therefore, to design and construct a thermal diffusion column free of the ramifications caused by the forgotten effect and to establish the operating characteristics of this column.
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