X-Ray Diffraction in Long Chain Liquids

The diffraction of x-rays in long chain liquids is calculated by the method of Zernicke and Prins. In the liquid, the long cylindrical molecules are arranged quite at random in space and orientation, except in so far as the condition for relatively dense packing necessitates that about any one long molecule, the nearest neighbors be roughly parallel. The main peak is due to a concentration of scattering matter at a distance about 8 percent larger than the lateral distance between chains. The inner peak, which is observed for the alcohols and the fatty acids, measures the distance from the heavy end group to the gap at the opposite end. For relatively long chains this distance becomes equal to the chain length.