Johann Wilhelm Hittorf (27.03.1824-28.11.1914) was a German physicist and chemist and a corresponding member of the Berlin Academy of Sciences (1884). He was born in Bonn, where he graduated from the university (1846) and worked. In 1852—90 he was professor at the academy (the university) in Münster.
His work was on the study of electrolytes, electric discharges in gases and cathode rays. He studied the motion of ions in electrolytes during electrolysis and developed in 1856 the theory of electrolytic conductivity. He studied the spectra of incandescent gases and the passage of electric current through a rarefied gas and in a vacuum. To study electric discharges in gases he used special tubes (Hittorf tubes). In 1869 he observed cathode rays and described their properties, in particular the production of a shadow by means of them (proof that they propagate in straight lines). He demonstrated the Paschen effect. He showed that heating the negative electrode makes a discharge in a vacuum easier (1884). He attempted to determine the limiting length of the positive column in a discharge tube. Together with J. Plücker he observed the spectra of various substances (hydrogen, nitrogen, sulfur vapour and others) and introduced the division of spectra into spectra of the first and the second order, band and line spectra. He held (1879) that the conductivity of gases rests on an ionic mechanism of conduction. He studied (1851) the conductivity of selenium. A member of a number of academies of sciences and scientific societies.