The Infra‐Red Transmission of Several Organic Compounds Near the Melting Point

The transmission of benzophenone, desoxybenzoin, diphenyl ketone, and benzalacetophenone has been measured at various temperatures. The spectra of the compounds are affected only slightly by change of state, the most marked difference being a variation in the intensity of certain bands. Isochromatic curves for benzophenone and desoxybenzoin indicate pronounced differences in background transmission at temperatures immediately below the melting point with a rapid increase at the melting point, while those for dibenzyl ketone and benzalacetophenone show only a rapid increase in transmission on melting. The data for benzophenone and desoxybenzoin are interpreted as indicating the existence of a mesophase near the melting point.