Photometry of X-ray crystal diffraction diagrams

X-ray crystal diffractions can be recorded on photographic films as spots, but these spots vary in area and are uneven in density. The first problem in any structural analysis is to obtain the integrated values of the intensities of the X-ray beams which produced the spots. The difficulties involved are outlined, and the various instruments which have been devised to perform this operation are briefly described. A new instrument, based on the principle of a rapid scan of the X-ray diffraction spot, similar to the scanning used in television, is also described.