Crystals of the monomer and polymer of the bis-ethylurethane of 5,7-dodecadiyne-l, 12-diol (1 a, ETCD, systematic name: 5,7-dodecadiynylene bis(N-ethylcarbamate) have been studied by X-ray powder and single-crystal photographic techniques. Lattice constants at 20 "C were obtained from both single-crystal and powder data and are in satisfactory agreement with a previous report. Lattice constants at 130-135 "C were obtained from powder data and reveal that the lattice expands in volume by 4% on heating from 20°C, in contrast to a previous report which indicated a volume contraction on heating. Rotation photographs of poly(ETCD) crystals before and after extraction of unpolymerized monomer with boiling methanol reveal that solvent extraction renders many reflections more diffuse. Weissenberg h0l-photographs of the polymer reveal sufficient disorder so as to preclude a high-precision structural determination. Rotation and Weissenberg photographs of monomeric ETCD at 20°C manifest the major reflections of the polymer.

With the explosive growth in the number of highly automated powder diffraction systems, many types of analyses which were previously considered a specialty analysis are now performed on a routine basis. Algorithms have been developed for measuring peak profiles from which crystallite sizes, residual microstrain, and X-ray crystal structure (Rietveld techniques for example) can be determined. However, these techniques require an instrumental peak profile calibration standard to correct the experimental data for instrumental broadening due to the system optics.Significant problems are encountered when laboratories try to cross-correlate or reproduce published data due to the lack of a common reference material for instrumental calibration. This is particularly distressing in microstrain and crystallite size calculations which can be dramatically affected by a poor choice of standard materials. Microstrain and crystallite size measurement are becoming increasingly important for the characterization of advanced materials and catalysts.

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A task group of the JCPDS—International Centre for Diffraction Data (ICDD) was established for the purpose of investigating a methodology which would be applicable for statistical process control monitoring of X-ray powder diffractometers. A procedure for collecting X-ray diffraction data for statistical process control purposes and the incorporation of these data into control charts are presented. The results of this task group show that, through the use of statistical process control methods, noncontrol situations for diffractometers were detected, the causes of these problems were identified, and these problems were corrected and noted on control charts.

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