HITTORF, JOHANN WILHELM German physicist, was born at Bonn, on March 27, 1824. He studied at Bonn and Berlin, and became privatdozent in the academy of Munster. When this institution became the university of Mun ster, Hittorf became professor of physics and chemistry; in 1879 the physics and chemistry departments were separated, and he became director of the physical laboratories. Hittorf retained this post until 1889 when he had to resign because of ill-health. After a rest his health improved, and he continued his research work. He died at Munster on Nov. 28, 1914.
Hittorf's early investigations were on the allotropy of selenium and phosphorus. His most important work on the migration of ions during electrolysis appeared in the Annalen der Physik be tween 1853 and 1859. He investigated the changes in concentra tion in the electrolyte and from this worked out the "transport numbers" for the migrating ions. Hittorf was associated with his teacher Plucker in a series of investigations on the spectra of gases and vapours. He made a number of investigations on the passage of electricity through gases, he discovered a number of properties of cathode rays and observed the Crookes' dark space. Other investigations were on the passivity of metals.
His monograph, Ueber die IVanderung der lonen wahrend der Elektrolyse, was republished by Ostwald in See obituary notices by Arrhenius in Zeitschrift fur Electrochemie 21 (1915) and by Heydweiller in Physikalische Zeitschrift 15 (1915) .