A light bulb is lit when the conductivity probe is immersed in an ionic solution.
The solutions are all in labeled 250ml beakers. All are about 150 ml of 0.1M sol'n. In order, the solutions are: tap water, distilled water, sodium chloride, sucrose, acetic acid, hydrochloric acid, sodium hydroxide, ethanol, and barium sulfate. (See video: http://youtu.be/4WillWjxRWw?hd=1)
The simple conductivity tester is on the bench, for the instructor to plug in. An 800ml beaker with 400 ml of distilled water is provided as a rinse station for use between samples.
See the discussion in Electrical Conductivity of Liquids, in Shakhashiri, B. Z. Chemical Demonstations: A Handbook for Teachers of Chemistry, Vol. 3; The Univ. of Wisconsin Press, Madison, WI, 1989; pp.326-328.
Gloves and safety glasses.