Preparation of Retinene in Vitro

RETINENE, obtained by Wald from dark-adapted retinas, is defined as the chromogen responsible for a maximum at 664 mµ in the absorption spectrum of the blue solution obtained by mixing retinal extracts with antimony trichloride in chloroform. Such extracts show (in chloroform) an ultra-violet absorption band with λ_max.385 mµ. It has recently been suggested¹ that the chromogen is vitamin A aldehyde, and that it can be obtained by direct oxidation of vitamin A alcohol.