SM085     Capillarity     circa 1950    Hydrostatics

  Capillarity phenomena are observed when solids are in contact with liquid surfaces.   If a body e.g. a glass rod is placed in a liquid, which wets it, the liquid will rise upwards against the sides of the solid.   The reverse is true when the liquid does not wet the solid.

  Laws of ascent or depression in a capillary tube:

  (a).   Jurin’s law states that for the same liquid, and the same temperature, the mean height of the ascent in a capillary tube is inversely proportional to the diameter of the tube.

  (b).   For the same liquid, and the same temperature, the mean heights raised in capillary tubes of the same diameter vary with the nature of the liquid.   (Of all liquids, water rises the highest)

  (c).   For the same liquid, and the same temperature, the mean heights are independent of the form of the capillary tube above or below the meniscus.

  (d).   Provided the liquid moistens the tube, neither its thickness nor its nature has any influence on the height to which the liquid rises.

  (e).   The height to which the liquid rises in a capillary tube diminishes as the temperature rises.

  (f).   Jurin’s law does not hold with the same accuracy when the liquid does not wet the solid