146 RECORDS 



Dr. L. Boroschek gave an account of some work he had 

 undertaken in connection with Dr. Tufts on the absorption of 

 Hght by some dyes of the fluorescein group. The dyes studied 

 were fluorescein and a number of its nitro-derivatives. 



It was stated that Hewitt and Perkins (^Journal Chern. Soc, 

 1900, page 1324) claim that a double symmetrical tautomerism 

 furnishes a satisfactory explanation for the fluoresence of Fluor- 

 escein, and that in the case of dinitro and tetranitro fluorescein 

 this tautomerism is inhibited by a secondary tautomerism be- 

 tween the nitro and hydroxy 1 groups when in ortho position to 

 each other. It was found that the mono-nitro-fluoresceins, ob- 

 tained by us by condensing the 3 -nitro and the 4-nitro-phthalic 

 anhydrides with resorcin, in which the nitro group is on a dif- 

 ferent benzol nucleus from the hydroxyl groups show no fluor- 

 escence in alkaline solutions. According to the theory of 

 Hewitt and Perkins alkaline solutions of such dyes should 

 fluoresce. 



Photographs of the absorption spectra of alkaline solutions 

 of the dyes were taken and it was found that the substitution of 

 nitro groups displaces the prominent absorption band of fluores- 

 cein toward the red end of the spectrum and increases the 

 absorption in the ultra violet. 



The absorption of light in the visible spectrum was studied by 

 means of the flicker photometer. The amount of light trans- 

 mitted by equal thicknesses of solutions of different concentra- 

 tions was measured for the various dyes. A relation was thus 

 obtained between the absorption of light and the concentration 

 of the dye. The work is still in progress. 



F. L. Tufts, 



Secretary. 



SECTION OF BIOLOGY. 



November i i, 1901. 



Section met at 8.15 P. M., Professor C. L. Bristol presiding. 

 The minutes of the last meeting of Section were read and 

 approved. 



