Previous measurements of the optical rotatory power of crystalline $\alpha$ — NiS${\mathrm{O}}_4$·6${\mathrm{H}}_2$O in the visible spectrum have now been extended to cover the wave-length range from 0.25μ to 2.2μ. Circular dichroism and absorption measurements have also been made over the infra-red range. Striking anomalies in the rotatory dispersion curve appear at 0.69μ and particularly at 1.16μ, corresponding to absorption and circular dichroism maxima at these wave-lengths. The theoretical relation between rotatory power and dichroism is verified quite exactly and in detail, particularly with regard to the 1.16μ band.

• Received 6 April 1940

DOI:https://doi.org/10.1103/PhysRev.57.1145