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.

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.

It has been the purpose of the present paper to investigate and explore the There has been an upsurge of research interest in molecular complexes of the donor-acceptor type during the last two decades (1). Despite the large number of papers dealing with molecular complexes, only a small percentage of these studies use nuclear magnetic resonance (NMR) spectroscopy as a means of determining complex formation equilibria, their compositions, and thermodynamic data. More recent papers include the work of Kuntz (2, 3), Foster (4, 5), Hanna (6, 7), and their coworkers. In particular, Hanna and Ashbaugh (6), observing the basic assumption of Huggins and Pimentel (8) for the correlation of the NMR measurements to the equilibrium, noted that equilibrium constants in hydrogen-bonding systems can successfully be determined by NMR spectroscopy (9), and that complex formation equilibria between donors and acceptors are similar to those found in hydrogenbonding systems. According to Hanna and Foster, if the concentration of acceptor is kept considerably lower than that of the donor, then the plot of the ratio of the observed chemical shift relative to however, be investigated in a later paper. Since in most NMR measurements, we keep CAO constant and vary CDO, it is convenient to define a set of dimensionless quantities as follows: K1* = K1 CAO; CDO* = CD0/CA0; CAD* = CAD/CA0M In terms of these dimensionless quantities, Eq. 3 becomes,

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Water continuum CO2 laser absorption spectra are reported for temperatures between 27 and -10 degrees C. The continuum is found to possess a negative temperature coefficient. The results obtained suggest that the magnitude of this temperature coefficient increases with increasing water pressure and decreasing temperature. The temperature coefficients between 27 and 10 degrees C for air mixtures containing 3.0- and 7.5-Torr water vapor are -2.0 +/- 0.4 and -2.9 +/- 0.5%/ degrees C, respectively. For mixtures with 3.0-Torr water the 10-0 degrees C temperature coefficient is -7.7 +/- 0.2%/degrees C. The temperature and water pressure dependencies observed for the continuum suggest that while both collisional broadening and water dimer mechanisms contribute to the continuum, the dimer mechanism is more important over this temperature range.