Diffraction of X-Rays in Liquids: Effect of Temperature

The effect of temperature upon x-ray diffraction has been examined for the following liquids: mesitylene, 4-hydroxy-1.3-dimethylbenzene, 2-hydroxy-1.3-dimethylbenzene, phenol, napthalene, benzene, cyclohexane, di-n-propyl carbinol, heptylic acid, tertiary butyl alcohol, lauryl alcohol, octane, 2.7-dimethyloctane and 2.4-trime-thylpentane. (1) The peaks shift in the intensity-diffraction angle curve toward smaller angles with increase in temperature, which varies in amount in different planer spacings in the same liquid; (2), the peak intensity varies with temperature differently for the different spacings in a single liquid, the principal maxima showing a decrease in the intensity for some liquids (class I), and an increase in the intensity for other liquids (class II) with increase in temperature; (3) a greater diffuseness of the principal maxima was found at high temperatures, attaining a greater magnitude for class I liquids; (4) the percentage increase in peak width per degree change in temperature is greater for class II than for class I; (5) boiling had no effect on diffraction phenomena, (6), increased scattering at small angles was noted at high temperatures, the effect being greater for class II.The foregoing results lead to the following conclusions. The evidence favors strongly the cybotactic space group condition of liquids and indicates that in some of the liquids space rearrangement within these groups takes place with changes in temperature. It may be said there is a change in molecular shape. Furthermore, within the groups of some liquids, expansion is apparently different in different directions, or internally anisotropic.