The relative vitamin A value of the body and liver oils of certain fish

IN view of the fact that the biological method for the estimation of vitamin A is not only tedious and expensive, but is open to errors of a rather disturbing magnitude, the need for a more satisfactory method has always been keenly felt. In 1925 Rosenheim and Drummond described the AsCl3 test as the basis of a quantitative method of assay, but the method was greatly improved by the use of SbCl3 and other modifications introduced by Carr and Price [1926]. Drummond and his co-workers have presented evidence that these colour reactions are of practical value in the assay of vitamin A in liver oils, and support for this view has been brought forward by Rosenheim and Webster [1926, 1927], Willimott and Wokes [1927] and others. On the other hand some investigators do not regard the reaction as specific for vitamin A. Some of their objections have been dealt with by Drummond and Morton [1929] and have been shown to be based on unsatisfactory evidence, but those raised by Schmidt-Nielsen were, however, more serious, in that superficially it did not appear that the discrepancies could be attributed to obvious differences of technique.