Morphological studies of benzene derivatives. V.—The correlation of crystalline form with molecular structure: a verification of the barlow-pope conception of "valency-volume."

The systematic crystallographic inquiry discussed in the present communication was commenced, about fifteen tears ago, in the hope that it would be possible, by determining the morphological characters of a considerable number of benzene derivatives of simple constitution, to discover relationships from which definite deductions could be drawn as to the precise manner in which crystalline form is affected by particular alterations in molecular configuration—the ultimate object in view being to correlate internal structure with external form. In planning the work, in order to determine the effect of all the possible variations of the position in the molecule of chlorine and bromine, it was decided to study, in the first instance, as many as could be procured of the di-substituted compounds of the form C6 H3 R1 R2 .SO2 X containing either chlorine of bromine in place of R1 , R2 and X.