The Structure of Gases

Other diffraction methods include electron diffraction, which may be used to determine the structures of gases or of volatile liquid substances that cannot be obtained as crystals suitable for x-ray diffraction, and neutron diffraction, which has special application for crystals in which the exact location of hydrogens is desired. Hydrogen does not have sufficient scattering power for x rays to be located precisely by x-ray diffraction. 

A specific example of how the nature of the carrier can influence the structure of gases adsorbed on dispersed metals is shown in Fig. 10. In this figure, A is the spectrum of CO chemisorbed on Cabosil-supported platinum and B is the spectrum of CO chemisorbed on 7-alumina-(Alon-C) supported platinum. 

There have already appeared artides reviewing the progress achieved in the fields of intermolecular forces, methods of statistical mechanics, and the structures of gases, liqiuds, and their molecular mixtures, including the critical region. De Voe reviews the theory of the conformations of biological macromolecules in solution, and Yomosa that of charge transfer in the molecular compounds of biolo cal systems. 

The physical behavior of a sample of gas can be described completely by four variables pressure (P), volume (V), temperature (T), and amount (number of moles, n). The variables are interdependent any one of them can be detennined by measuring the other three. We know now that this quantitatively predictable behavior is a direct outcome of the structure of gases on the molecular level. Yet, it was discovered, for the most part, before Dalton s atomic theory was published ... 

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