In the preceding papers (This Journal, 15, (1949), 267, 270) the author assumed that the first necessary condition for discolorating fish oil is oxidation of oil. Mere oxidation of oil occurs no discoloration, but when certain volatile basic nitrogen compounds react to this oxidized oil, the color of the oil will become dark-red.
In this paper the author has confirmed his assumption by the following experiment.
Fresh shark liver oil was oxidized by blowing the air into it under the dispersed light and in the room temperature. Three of 20cc. oxidized oil were taken out each time and some chemical properties and the color of the control oil was measured on one of these three samples (A). The remaing two were treated with 5cc. of Aq. Dest. (B) or 5cc. of strong (28%) Ammonia (C) respectively just 5 minuts in the boiling water bath and the properties of these treated oil was compared with A. (see Table 1 and 2),
In the tables it is clearly pointed out that the color of the fish oil will not become darkly red by simple oxidation process, but when a certain volatile basic nitrogen compounds react to this oxidized oil the color becomes deep, and the degree of the color, depth become much larger, keeping pace with the proceeding, of oxidation. The author has found a fact that the odor of the above mentioned darkly red oil is like that of fishmeal.
