Liquid column put in conical tube moves by itself to more narrow part when it wets tube walls and to wider part when it does not wet the walls. Explain the phenomenon.
In case of wetting liquid its surface has concave form. Under concaved meniscus pressure is lower than under flat meniscus, pressure on the least concaved surface of the tube turned to wider end of the tube is stronger than on the opposite side. That is why the column moves to the narrow part. In case of unwettening the surface has convex form; pressure is stronger under convex meniscus, big convexity from the narrow part of the tube that’s why column will move to wider part.