“…Some early studies of the antimony trichloride reaction with oils (163,164,243) showed that the color was not pro portional to the concentration of vitamin A; however, re sults obtained with the nonsaponifiable fraction gave a more linear relationship (40,206,242)* These values checked reasonably well with the biological method (40,107,206)* Much of the early spectrographic data concerning the color developed by reaction of vitamin A with antimony tri chloride has been reviewed by Munsell (153). Under suitable conditions it was found that the absorption at certain wave lengths were altered by changing concentration, temperature or by adding certain chemicals (19,55,145,165). It is now quite generally agreed that vitamin A in any of its forms possesses a single strong absorption band at 620…”