SEPARATION BY PAPER CHROMATOGRAPHY 265 



Ai-propanol, 30 cc. concentrated ammonia solution, and 10 cc. water. He has 

 also found useful for detection of ultraviolet absorbing spots a sheet of paper 

 impregnated with proflavine as a fluorescent screen. 



The circular method of paper chromatography of Rutter^"^ and others, 

 for which improved resolution is claimed, has been applied to nucleic acid 

 derivatives.^"^ 



A comprehensive tabulation of ultraviolet absorption data, including 

 molar extinction coefficients and the r.atios of extinctions at different wave- 

 lengths, measured at three pH values, has been prepared by Volkin and 

 Cohn.ii" 



'08 L. Rutter, Nature 161, 435 (1948). 



'"^ K. V. Giri, P. R. Krishiiaswamy, G. D. Kalyankar, and P. L. N. Rao, Experientia 



9, 296 (1953). 

 ''" E. Volkin and W. E. Cohn, in "Methods of Biochemical Analysis," (D. Glick,ed.) 



Vol. 1, Interscience Publishers, New York (1954), and m "Methods in Enzy- 



mology" (S. P. Colowick and N. O. Kaplan, eds.), Vol. 2, Academic Press, New 



York (in press). 



