Investigations on magne-crystallic action. Part I.-Diamagnetics

Abstract It is well known, from the investigations of COTTON and MOUTON and others* on the magnetic double-refraction of liquids, that diamagnetic molecules in general are magnetically anisotropic. When such molecules are arranged in a regular manner as they are in a crystal, the crystal, as a whole, will usually exhibit differences in susceptibility in different directions. The magnitude of these differences will evidently depend on the relative orientations of the molecules in the unit cell; their positions in the cell will have no direct effect, since the diamagnetic moments induced in the molecules are so feeble that their mutual influences are negligible.* Thus a correlation of the magnetic anisotropy of the crystal with that of the individual molecules constituting it, calculated from measurements on magnetic double-refraction in the liquid state, or from other considerations, is likely to give us useful information regarding the orientations of the molecules. This method of analysis of molecular orientations in crystals, which was first suggested by one of us, promises, at any rate, in favourable circumstances, to be a useful supplement to X-ray methods of crystal analysis. Indeed, in certain crystals—as will be seen in the body of the present paper—the molecular orientations can thus be determined more easily and with greater accuracy than by X-ray methods.