The use of a stream of electrons to study the atomic structure of metals and gases and to identify invisible layers of films of foreign materials on metal surfaces has been developed into a practical process in the chemistry laboratoires of the University of Michigan. This provides an "electron diffraction" method of analyzing metal surfaces which permits a wide variety of practical applications in the fields of welding, lubricating, electroplating, and painting. A machine based on an experimental model developed by Professor Lawrence O. Brockway is now on the market for this purpose.
This machine produces a streamof 40,000-volt electrons in a vacuum chamber. In the center of the chamber is a specimen holder on which the piece of metal to be studied is placed. This metal interrupts the electron stream so that the electrons bend or break off into new paths. As they do so, they expose a photographic plate thatis inserted at the end of the chamber.
Every metal breaks up the electron stream in a distinct pattern so that photographs resulting from this process are different for each metal. It is, therefore, possible to identify unknown substances in the electron stream by comparing their "diffraction patterns" or photographs with those of substances already identified.