Diffraction Pattern and Structure of the System Water–Ammonia at 4°C

The scattering of x rays from the free surface of liquid solutions of ammonia in water and of pure ammonia at 4°C has been analyzed. Intensity and radial distribution functions have been calculated for a model structure and compared with those derived from experiment. This model, similar to that proposed for liquid water, assumes an anisotropically expanded ice I structure, surrounded by a continuous distribution of distances, as an adequate description of the short-range order in these liquids. Occupancy of the large dodecahedral cavities typical for this structure was permitted. The model intensity and radial distribution functions are in quantitative agreement with those derived from experiment.