FACTORS AFFECTING THE SURFACE-CHEMICAL DISPLACEMENT OF BULK WATER FROM SOLID SURFACES.
NAVAL RESEARCH LAB WASHINGTON D C
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Bulk water films can be displaced from a solid surface by a spreading organic liquid which creates and maintains a surface tension gradient in the airliquid interface. Such a gradient can be maintained if the spreading agent escapes from the airwater interface by solution or evaporation after a few centimeters of travel away from the point of application. The resulting movement of the surface film sweeps along the water beneath by viscous entrainment Marangoni effect. Displacement is effective and lasting only when the displacing agent or a surface-active material dissolved in it is strongly adsorbed to form an insoluble hydrophobic film on the solid surface. Effective water-displacing agents at 20C should have the following properties a spreading pressure above 25 dynescm on water a boiling point above 90C, and a solubility in water of between 2 and 25 percent by weight. The equilibrium spreading pressures for members of a given class of polar organic compounds decrease with rising boiling point. These principles are well exemplified by a solution in normal butanol of 3 percent of basic barium dinonylnaphthalene sulfonate. Such water-displacing agents have been found suitable in numerous applications. Author
- Organic Chemistry
- Physical Chemistry