The preparation and properties of a semisolid nickel sulfate-sorbitol complex are described. The absorbance curve of the complex corresponds closely with that of an approximately saturated solution of hydrated nickel sulfate in water with the advantage of a two-fold increase in absorbancy index at the peak absorption. Used as a filter component it eliminates the undesirable properties of a liquid filter. A freshly made 3.5-mm thickness of complex had an average transmittance at 2850 A of 75% which showed a slight decrease after three years. An appreciable loss of transmittance after nine years arises from the development of an absorption band at 2850 A. The relationship of this band with a temperature-sensitive band in water solutions of pure nickel sulfate is discussed. The filter remains visually clear indicating that the complex has not crystallized in nine years.
Louis A. STRAIT, FRANK M. GOYAN, and W. D. KUMLER, "Semisolid Nickel Sulfate Filter," J. Opt. Soc. Am. 46, 1038-1038 (1956)