Pendant Drop Test
In the pendant drop test, a drop of liquid is suspended from the end of a tube by surface tension. The force due to surface tension is proportional to the length of the boundary between the liquid and the tube, with the proportionality constant usually denoted . Since the length of this boundary is the circumference of the tube, the force due to surface tension is given by
where d is the tube diameter.
The mass m of the drop hanging from the end of the tube can be found by equating the force due to gravity with the component of the surface tension in the vertical direction giving the formula
where α is the angle of contact with the tube, and g is the acceleration due to gravity.
The limit of this formula, as α goes to 90°, gives the maximum weight of a pendant drop for a liquid with a given surface tension, .
This relationship is the basis of a convenient method of measuring surface tension, commonly used in the petroleum industry. More sophisticated methods are available when the surface tension is unknown that consider the developing shape of the pendant as the drop grows.
Read more about this topic: Drop (liquid)
Famous quotes containing the words pendant, drop and/or test:
“Phlébas, le Phénicien, pendant quinze jours noyé,
Oubliait les cris des mouettes et la houle de Cornouaille.”
—T.S. (Thomas Stearns)
“Do they merit vitriol, even a drop of it? Yes, because they corrupt the young, persuading them that the mature world, which produced Beethoven and Schweitzer, sets an even higher value on the transient anodynes of youth than does youth itself.... They are the Hollow Men. They are electronic lice.”
—Anthony Burgess (b. 1917)
“To answer a question so as to admit of no reply, is the test of a man.”
—Ralph Waldo Emerson (1803–1882)