A Provitamin A other than Carotene?

Abstract

A TURBOT concentrate estimated by spectrographic and colorimetric tests to contain 60 per cent vitamin A (the vitamin A of Carr and Jewell¹ taken to be 100 per cent) was irradiated in spectroscopic alcohol in the complete absence of air with light of wavelength 300–390 mμ. Solutions containing 0.0011 per cent vitamin A were found to be only slightly affected by exposures up to three hours' duration whilst solutions containing 0.00011 per cent were remarkably sensitive. Solutions of this latter concentration were irradiated in lots of 60 ml. for different periods and kept stirred during irradiation by a magnetic stirrer. After irradiation of one lot it was evaporated in vacuo at 50° and brought to such a concentration as was equivalent spectroscopically at 328 mμ to a solution containing O.OOll per cent vitamin A. Its absorption curve in the ultra-violet and its blue value were then determined.