The Rise and Fall of N-Rays

      The saga of N-Rays provides a good introduction into experimental design. It is easy to understand and therefore quite suitable for introductory general chemistry classes, where it can be discussed in conjunction with topics such as X-rays.

Figure 1. René Blondlot

    René Blondlot was a distinguished professor of physics at the University of Nancy, France, a corresponding member of the Academy of Sciences, and the recipient of a number of scientific awards. Professor Blondlot, while trying to polarize X-rays which had been recently discovered by Roentgen, claimed in 1903 to have discovered a new invisible radiation which he called N-rays (in honor of his home town of Nancy). He used prisms and lenses made of aluminum to focus and disperse the N-Rays, and he detected the spectrum by passing a fine thread, coated with fluorescent material, across the focal plane. His results were replicated by a number of laboratories. Numerous claims were made for N-rays, such as they could be conducted along wires, like electricity.
    Blondlot was visited by American spectroscopist Robert Wood (author of the classic book "Physical Optics", and discoverer of the phenomenon of atomic fluorescence), who had tried to duplicate the N-ray experiments, but failed. A number of experiments were performed in Wood's presence. First, N-rays were focused on an electric spark and the brightness of the spark was supposed to increase when the N-rays were present.  Wood saw no effect and was told that his eyes weren't properly sensitized.
    Next, Wood was shown several photographs which supposedly showed a brightening of the spark image, but they were made under conditions that were subject to a number of errors.
    Finally, Wood was shown how the N-rays were refracted by an aluminum prism in a spectrometer whose entrance slit was a piece of wet cardboard with a slit cut into it. Wood was suspicious, because the slit of Blondlot's N-ray spectrometer was 3 mm wide, yet Blondlot could detect changes in spectral intensity on the order of 0.1 mm at his focal plane. Wood asked Blondlot to demonstrate the apparatus, and secretly removed the aluminum prism from the N-ray spectrometer in the darkened room when Blondlot could not see him. Yet Blondlot continued to see the N-ray spectrum. Wood published his results in Nature (Vol 70, p.530, September 29, 1904), and N-rays disappeared from the scientific literature within several years.
    This story has been told many times, and was discussed by Irving Langmuir as an instance of pathological science in his 1953 lecture that was reprinted in PHYSICS TODAY, Oct 1989, p. 36. But there's more to the story. There are inconsistencies between Robert Wood's original article and another published in 1940, and some have claimed that Wood never removed the prism and this was another one of his pranks.
    Sour grapes? Probably, but Wood once used his redoubtable talents in optics to fabricate what must have been one of the first photographs of an Unidentified Flying Object (UFO). He has been described as a showman who long after adolescence was "an inveterate perpetrator of pranks and hoaxes." But it was likely Wood's ability to understand the mechanisms of pranks and hoaxes that led to his unraveling of the N-ray affair. He went into such a situation with the intent to disprove the effect if possible, rather than an intent to reproduce the effect. Scientific research carried out with the latter objective can have disastrous consequences.  Have we seen this recently?  How about polywater and cold fusion.  The axiom that we learn most from our mistakes holds as true in science as it does in any other form of human endeavor.
    One of the best sources of information concerning Robert Wood and N-Rays is the sociological study of N-rays by Malcolm Ashmore: The Theatre of the Blind: Starring a Promethean Prankster, a Phony Phenomenon, a Prism, a Pocket, and a Piece of Wood, Social Studies of Science, Vol. 23 (1993), 67-106, which also provides an extensive bibliography.
    There are a number of ways that this parable can be included in the chemistry curriculum.  In general chemistry, it can be a sidelight to a discussion of X-rays and dispersive spectrometers associated with analysis of  crystal structures and Bragg's law.  In more advanced courses, such as instrumental analysis, the use is obvious.

[Thanks to Professors Marcello Truzzi and Ray Hyman for much of the information and references on the saga of N-rays]

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Page prepared by: Mike Epstein
Last Modified: 30 April 1999