Absolute Intensity Measurements in Small-Angle X-Ray Scattering

The absolute intensity of small-angle x-ray scattering has been measured by two methods—comparison with a beam transmitted through a series of similar attenuators, extrapolated to the case of no attenuators, and comparison with the scattering of air—with good agreement. Some reproducible substances are calibrated as standards at small angles and some also at larger angles, in the range accessible to the diffractometer. Brief interpretations are given of the small-angle scattering; that of water is consistent with theory. The long-range density fluctuations of vitreous silica are found to be mainly those frozen in at the glass transformation. The absolute scatterings are compared with Katz's unpublished small-angle standardization and with Warren's standardizations of Lucite and vitreous silica by means of high-angle scattering. Katz's measurements of silica and Warren's of Lucite are appropriate for quantitative comparison. They are about 2% higher and 7% lower, respectively, than the present result. Finally, the effect of impurities is derived.