Limiting Factors for Diffraction in the Gandolfi X-Ray Camera

Abstract

A discrepancy was discovered between an experimental X-ray diffraction pattern of sodium acetate trihydrate collected with the Gandolfi camera and a calculated pattern based on a single crystal study of the same compound. The experimental d spacings matched those of the calculated pattern with the exception of the strongest reflection d = 3.002 Å (h k l = 40 − 2) which was missing in the experimental pattern. Another experimental Gandolfi pattern obtained from a powdered sample of sodium acetate trihydrate gave excellent agreement with the calculated d spacings and intensities.

The results of our investigation into this discrepancy show that the angle θ, crystal alignment, camera diameter, and the crystal system can affect diffraction in the Gandolfi camera. It is shown that all reciprocal lattice points with θ angles less then 10.08° would diffract in the film plane of the 114.6 mm Gandolfi camera and points with θ angles less then 20.49° would diffract in the film plane for the 57.3 mm camera regardless of the crystal system or alignment. However, reciprocal lattice points aligned along the spindle axis of the 114.6 mm Gandolfi camera having reciprocal lattice points with Z ≥ 0.35 reciprocal lattice units (r.l.u.) and X and Y ≤ Z-0.35 r.l.u. will not diffract into the recording plane of the Gandolfi camera. The reciprocal lattice points aligned along the spindle axis of the 57.3 mm Gandolfi camera with Z ≥ 0.70 r.l.u. and X and Y ≤ Z-0.70 r.l.u. will not diffract into the recording plane of the camera.