ANALYTICAL EDITION
May, 1944
with decreasing potency, will make the validity of this assumption more apparent. The satisfaction of condition 3-i.e., that irradiation is continued long enough to ensure complete decomposition of the vitamin-is apparent from Figure 4. Pure vitamin A in cyclohexane was completely destroyed in about 15 minutes, and in 30 minutes or less it was eliminated in the cases of liver and of muscle. The condition most difficult to satisfy is KO.2-i.e., the irradiation produces no appreciable change in the absorption a t 3280 A. of substances present other than vitamin A. The specificity of the irradiation for the vitamin is well demonstrated, however, for all types of materials studied, in the absorption curves of Figures 5 and 6. The primary change occurs a t 3280 8., all other changes being secondary in magnitude. T h a t the satisfaction of these conditions is possible only by using filtered light radiations is illustrated by Figures 2 and 3 Condition 2 is definitely not satisfied when the light radiations used contain wave lengths which coincide with the absorption maxima of substances present other than vitamin A. I n Figure 3, the nature of the curve obtained with filter 1 could mean two things: (1) The decomposition of the vitamin is paralleled and followed by the decomposition of other constituents of the solution, or (2), as suggested by Demarest, the vitamin is screened from the effective radiations by the absorption of other constituents. The result of this second effect would be a much greater irradiation time required to obtain complete destruction of the vitamin. The value of a method of vitamin A assay employing destructive irradiation is apparent in the application of the method to oils of a wide range of potency, as shown in Table 11. Direct measurement of the whole oil dilution has often been employed in the case of high-potency oils, common practice having been to dispense with saponification for oils with a potency of 10,000 I.U. per gram or more. Direct measurement of unsaponifiable preparations is applicable to potencies of approximately 2500 I.U. per gram or more. The applicability of the irradiation technique used on whole oil preparations is even lower than this, and would probably go to values of 1000 I.U. per gram or less. Employing both saponification and irradiation, the assaying of oils as low as 200 I.U. per gram or lower is possible. These limits will, of course, vary with the nature of the material assayed, and with the saponification and extraction technique used. I n the light of what has been said thus far, it would seem that E11% cm. mod. or irrad. might be more dependable measures of vitamin A potency than The results obtained with the second U.S.P. oil (Table I) indicate the introduction of a n error of 8 to 12% by the assumption that Et is ameasure of vitamin A only. This error would carry over into calculated instrument factors and any spectrophotometric assays made on other preparations, using this factor. The similarity of the factors calculated from E:?m. irrad. for V.S.P. oil 2 a n d E ; z m . for U.S.P. oil 1 (2500 in each case) suggests that the extraneous absorption in the case of the latter was small enough a t 3280 A. to give rise to no significant error in direct measurement. This is indicated, but not proved, by the results obtained with oil 3 in Table 11. It would seem possible, on the basis of the work presented, that the destructive irradiation technique may be the means of increasing the scope of the determination of vitamin A by in vitro methods. Certainly the value of for preparations of materials containing vitamin A should be interpreted carefully, unless considerable research has been done on substances of comparable chemical nature, with respect to the nature of the absorption curve and the effects of irradiation.
Fm.
ACKNOWLEDGMENT
The author wishes to take this opportunity to express his sincere gratitude to Arthur W. Thomas for his interest and helpful criticisms throughout this investigation.
293 LITERATURE CITED
(1)
Baumann, C. -4., Riiing, B. Y.,and Steenbock, H., J . Biol. Chem., 107, 705 (1934).
Carr, F. H.. and Price, E. A., Biochem. J . , 20, 497 (1926). Davies, A. W., Ibid., 27, 1770 (1933). Davies, A. W., and Moore, T., Ibid., 28, 288 (1934). De, N. K., Indian J . Med. Research, 24, 737 (1937). Demarest, B., 2.Vitaminforsch., 9, 20 (1939). (7) Dornbush, A. C., Peterson, W. H., and Olson, F. R., J . Am.
(2) (3) (4) (5) (6)
M e d . Assoc., 114, 1748 (1940). (8) Edisbury, J. R., Analyst, 65,484 (1940). (9) Hume, R. M., and Chick, H., Med. Research Council, Ypecial
(10)
Rept., Sw. 202, I V (1935). Little, R. W., Thomas, A. W., and Sherman, H. C., J . Biol.
(11)
McAlister, E. D., Smithsuniarz Misc. Collections, 87, No. 17
(12)
McFarlane, W. D., and Sutherland. A. J., Ca?i. J . Research, 16,
Chem., 148, 441 (1943).
(1933). 421 (1938).
Moore, T., Biochem. J . , 24,692 (1930). Neal, R. H., Haurand, C. H., and Luckmann, A. H., IND.ENO. CHEM.,ANAL.ED., 13, 150 (1941). (15) Peacock, P. R., Lancet, 11, 328 (1926). (16) Saunders, F., J . Optical Soc. Am., 16, (1928). (17) Wilkie, J. B.. J . Assoc. Oficial Agr. Chsm., 23, 336 (1940).
(13) (14)
A P A R T of the thesis of Robert W. Little submitted to the faculty of Columbia University in partial fulfillment of the requirements for the degree of doctor of philosophy.
A
Funnel for Use with Standard T a p e r Flasks RICHARD KIESELBACH Bakelite Corporation, Bound Brook,
A
N. J.
TIME-HONORED method of adding solids t o narrowmouthed containers involves the use of a sheet of paper rolled into a funnel. Every chemist is familiar with the drawbacks of this device, and most of them have managed to spill an embarrassing amount of material in its use. An important routine analysis in this laboratory requires the quantitative transfer of a fairly large amount of solid to a small weighing bottle having a standard taper stopper. The awkwardness of balancing a paper funnel in this operation, and the danger of loss of material in the fold of the paper, definitely suggested an improvement in this line. The funnel shown in the illustration was accordingly constructed, and has been found highly satisfactory in practice. Because i t fits firmly into the neck of the flask, the question of balancing is obviated. Since it is made of glass, the danger of particles sticking or getting lost in cracks is greatly reduced. The slope of the walls being fairly steep, solids do not tend to pile up in the funnel. The funnel has also been found useful in pouring large amounts of liquids and f : ~ ; ~ 8 0 msolids ~ into other R p o Im flasks, with and without ground 2 joints, as the p o u r i n g is speeded by the steep walls a n d wide stem open$ 24/12 ing.
