A note on the photoactivity of cod liver oil

Abstract

As a preliminary step in the investigation of the relationship between cod liver oil and ultraviolet radiation as antirachitic factors, the experiments of Kugelmass and McQuarrie 1 on the photoactivity of cod liver oil were repeated. In every case negative results were obtained.

An apparatus similar to that described by these investigators was employed. Eastman's Speedway plates, possessing properties similar to Seed's Graflex 60, were used. Since these plates proved to be sensitive to the red light in the room, the whole experiment was carried out in total darkness. The cod liver oil was a sample of Mead and Johnson's, guaranteed as to vitamin activity. The apparatus was so arranged that a slow stream of dry oxygen was passed continuously over the surface of the oil during the exposure.

A twenty-four and sixty-six hour exposure to the oxidizing cod liver oil, made alkaline with 10 per cent potassium hydroxide, produced no darkening of the photographic plate. A seven-day exposure to the oil, untreated by alkali, also produced no effect. These results gave no evidence that cod liver oil, while oxidizing, emits ultraviolet light. That oxidation of the oil plays no part in its action as an antirachitic factor would be expected from the findings of McCollum, Sirnmonds, Becker, and Shipley 2 that, when air is bubbled through cod liver oil heated to 100° for 10 to 20 hours, vitamin A is destroyed, but the oil is still as effective as the untreated oil in curing rickets.