A study, by high-temperature diffractometry, of the monoclinic-tetragonal phase changes in pure ZrOz and HfOz disclosed that the hysteresis loops associated with the transformations have similar shapes which are typical of many martensitic phase changes, but that the widths of the loops differ greatly for the two materials, being about 200°C for zirconia and only 20' to 30°C for hafnia. The temperature-induced transformations are predominantly athermal. The nature of these and similar transformations is discussed. The reversible formation of a cubic form of ZrOz above 22OOOC was confirmed.

The first paper in this series [1] described the application of particle analysis to the identification of gunshot residue. In the course of developing this application, gunshot residue was identified in each of several hundred samples collected. In many instances, the nonfiring hand was sampled as a control, or “handblank” samples were taken from persons who had not fired a gun [2]. Some of these many tests were performed “blind,” that is, without prior knowledge by the analyst of the nature of the sample. No false positives were obtained from nonfiring samples. Nevertheless, it was thought that better proof of the uniqueness of gunshot residue particles was required and that an investigation should be made of the possibility that particles in the natural environment or particles produced by man could closely resemble gunshot residue.

No abstract

Several methods of bulk elemental analysis, such as fiameless atomic absorption, flame emission spectroscopy, neutron activation analysis, and photoluminescence spectroscopy, can reliably and quantitatively determine the amounts of antimony and barium (antimony and lead in the case of photoluminescence) removed from the hand. The information thus furnished, however, in most cases is not sufficient to constitute presumptive evidence of the presence of gunshot residue. Many analyses are inconclusive because the amounts of antimony and barium (lead) are less than certain “thresholds” considered necessary because these elements are not unique to gunshot residue. Firings from .22 caliber weapons, unless the cartridge is known to be a Federal brand, are not usually analyzed because domestic rimfire primers, except Federal, do not contain antimony. Understandably, there has been great interest in alternative analysis methods capable of furnishing additional information of potentially higher specificity for gunshot residue.