The relation between the crystal-symmetry of the simpler organic compounds and their molecular constitution.—Part I

Certain relations between the chemical composition of bodies and their crystalline forms indicate that the crystallographic properties depend in a simple way on the chemical constitution. There are three distinct relations which principally point towards such a connection. 1. The Isomorphism shows that similarly constituted compounds, even of a very complicated chemical composition, crystalline in a very similar way when certain atoms in the molecule are replaced by chemically related atoms. There are probably few subjects in the whole field of chemistry upon which so much separate evidence has been collected. As a result of all this research upon isomorphic relationship and isomorphic series, from that of Mitscherlich up to the recent work of Tutton, it may be concluded with a great amount of certainty that to a definite molecular edifice belongs a certain crystalline edifice. In consequence, the replacement of one or several atoms in such a molecular structure by atoms chemically closely related does not imply more than a slight alteration in the crystal form.