A lecture experiment to illustrate osmotic pressure

530

JOURNAL

or Crrenarc~~ EDUCATI~N

MAY,192

A LECTURE EXPERIMENT TO ILLUSTRATE OSMOTIC PRESSURE H. C. KREMERS,UNIVERSITY

OF

ILLINOIS, URBANA, ILLINOIS

Recalling a very simple and impressive experiment from college days the writer has found that the phenomenon of osmotic pressure may be simply and convincingly demonstrated as follows: A large carrot, beet, winter radish, turnip, or similar root is bored out by means of a one inch auger bit. The cavity thus formed is filled with a heavy table sirup or molasses and a stopper with glass tube attached is placed in position as shown in the accompanying sketch. The stopper should be well sealed with paraffin and wired in. The osmotic pressure cell thus made is immersed in a beaker of water. The osmotic pressure will cause the liquid to rise in the tube to a height of eight feet or more.