SECTIONAL TRANSACTIONS.—B. 361 
Prof. I. M. HritBron, F.R.S., and Dr. R. A. Morrvon.— Spectroscopy 
and Vitamin A. 
Fish and mammalian liver oils and concentrates exhibit an absorption band in 
the ultra-violet (maximum 328y,,), the intensity of which has been found to vary over 
the range 1—20,000, and which can be determined to within + 5 per cent. With 
antimony trichloride the same materials give a blue solution, the depth of colour 
extending over the range 1—60,000 at least. The blue solutions exhibit initially two 
absorption bands (maxima 572-583, 600-620u2), either of which may be so much 
more intense than the other as to make detection of the second band difficult in 
extreme cases. The longer wave-length band is usually the stronger, but the shorter 
wave-length maximum can always be detected by applying the colour test in a modified 
form, ;. of the usual quantity of reagent being used 1-14 minutes before the rest 
isadded. This procedure depresses the 600-620uu band without noticeably affecting 
the 562-583. band. 
Tn many instances the latter band predominates in the colour test. If an oil 
giving this result is exposed to the action of ozonised oxygen or hydrogen peroxide, 
a considerable increase in the intensity of the 600-620uu. band is usually seen when the 
oil is re-tested with antimony trichloride, but this increase is not at the expense of the 
562-583uy, band. 
Liver oils thus contain two chromogenic substances which behave as separate 
entities although the evidence does not excludekinship. The 562-583. chromogen 
varies directly asthe 328 absorption band, but the 600-620up. band and the 328yup. 
maximum appear to arise from different substances. Comparisons of physica] with 
biological data on a series of oils and concentrates indicate that the 328uu band and 
_ the 562-583. component in the colour test are valid quantitative criteria of vitamin 
A potency. 
: The available evidence concerning the molecular weight of vitamin A and the 
percentage of the richest concentrates unaccounted for as inactive substances leads 
_ toa very high molecular extinction coefficient (order 10°) at 328uy, and a chromogenic 
value for the intensity of the blue colour with antimony trichloride many times greater 
than that of any known sterol or carotinoid. 
Prof. R. Kuun.—Preparation of Isomeric Carotenes and their Biological 
Effects. 
Three different methods for the preparation of «-carotene have been worked out 
which, regardless of the source of the material, lead to products having identical 
absorption spectrum and optical activity. The ratio between a- and {-carotene 
varies significantly in green plants. The pigment of palm-oil contains relatively the 
largest amount of «-carotene. On the other hand, the carotene in ovaries is optically 
inactive. 
The effect of the purest preparations of the carotene components on the growth 
of rats will be described, especially the effect of preparations which have been purified 
by partial oxidation and by other chemical methods. Finally, a report will be made 
on the physical and biological examination of the liver oils obtained after feeding rats 
with «- and B-carotene. 
——-  * ~ 
_ Dr. T. Moorz.—Steps in the Concentration of Vitamin A. 
Although the high vitamin A content of mammalian livers has long been realised, 
most serious attempts at the isolation of the vitamin have been based on the use of 
_ eod-liver oil, or some similar fish-liver oil, as the starting material. Concentrates 
_ prepared from cod liver oil are not usually effective in rat tests at doses lower than 
0-01 mg., and give values of 200-400 blue units per mg. in the antimony trichloride 
reaction. (A typical cod liver oil before treatment may be taken as giving about 
1-0 B.U. per mg.) Almost all natural mammalian liver oils are richer sources of the 
vitamin than cod-liver oil, although this superiority may be set off against the much 
‘smaller amount of oil present per unit of liver. The mammal offers an additional 
advantage in being amenable to artificial feeding before treatment of the liver, by 
which means the vitamin A content may be raised to very high levels. 
Experiments have been carried out upon several groups of rats which have received 
in their diets either carotene (as 15 per cent. of red palm oil) or preformed vitamin A 
