Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Anode ray

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Canal ray tube schematic showing the rays to the right of the perforated cathode

Anode rays (or Canal rays) are beams of positive ions that were observed in experiments by the German scientist, Eugen Goldstein, in 1886.[1] Later work on anode rays by Wilhelm Wien and J. J. Thomson led to the development of mass spectrometry.


Goldstein used a gas discharge tube which had a perforated cathode. A "ray" is produced in the holes (canals) in the cathode and travels in a direction opposite to the "cathode rays," which are streams of electrons. Goldstein called these positive rays "Kanalstrahlen" - canal rays because it looks like they are passing through a canal. In 1907 a study of how this "ray" was deflected in a magnetic field, revealed that the particles making up the ray were not all the same mass. The lightest ones, formed when there was some hydrogen gas in the tube, were calculated to be about 1837 times as massive as an electron. They were protons.


  1. Grayson, Michael A. (2002). Measuring mass: from positive rays to proteins. Philadelphia: Chemical Heritage Press. pp. 4. ISBN 0-941901-31-9.