Friedrich Kohlrausch, a German physicist who did pioneering work on how electricity is transmitted in solutions, was born on this day in 1840. Kohlrausch is best known for a method to measure electrical conductivity using an alternating current, which determined that conductivity is lower in more dilute solutions. Kohlrausch also showed that there are two molecular players involved in conductivity: the cation, or positively charged ion, and the anion, or negatively charged ion.
[Source: Trevor I. Williams, Ed. A Biographical Dictionary of Scientists, Third Edition. John Wiley & Sons. New York. 1982.]