144 Intelligence and Miscellaneous Articles. 



ON TWO NEW FLUORESCENT SUBSTANCES. BY E. LOMMEL. 



Prom Dr. Th. Schuchardt, of G-orlitz, I received, some time since, 

 two new fluorescent substances, the examination of which (by the 

 method I have previously described) gave the following results. 



1. Anthracene-Blue. — The deep-blue etheric solution fluoresces 

 intensely olive-green. The absorption-spectrum shows four dark 

 bands, the darkest parts of which are situated at 36, 55, 69, and 

 86, respectively, of Bunsen's scale, and a darkening of the violet 

 end, commencing a little before H, while the blue and the greater 

 part of the violet appear almost unaffected. Of the absorption- 

 bands the second and the third (55 and 69) are by far the most 

 intense and about equal in intensity ; then follows, in the order 

 of intensity, the rather feeble first (36) ; and last comes the still 

 feebler fourth (86). The spectrum of the light of fluorescence 

 begins faint at 27, distinct at 30, and extends distinct as far 

 as 70, faint as far as 74. It shows three maxima, at 40, 52, 

 and 63, separated by two very clearly marked minima (at 45 

 and 57), and hence appears to consist of three bright bands — 

 one red, one orange-yellow, and one green-yellow — of which the 

 middle one a little exceeds the others in brightness. The fluo- 

 rescence-spectrum projected upon the liquid commences faintly at 

 47, and shows two very bright fluorescence-bands corresponding to 

 the two most intense absorption-bands, divided by a tolerably dark 

 interspace, and strongly distinguished from one another by their 

 different colouring ; namely, the first is entirely orange-coloured, 

 the second yellow-green. A third, but much fainter, brownish 

 olive-green-coloured maximum at 86 corresponds to the fourth 

 absorption-band; the first, on the contrary, has no part in the 

 fluorescence. In the blue and the violet, from F to shortly before 

 H, the fluorescence is very slight, olive-green to reddish, and 

 scarcely perceptible ; only just before H does it again become more 

 intense, and extends with an olive-greenish tone into the ultra- 

 violet. We have here, therefore, a fluorescing substance, with 

 which the blue and the greater part of the violet rays exert only an 

 extraordinarily feeble, while the orange-yellow and yellow-green rays 

 exert a very intense excitant action. If we excite with homogeneous 

 light, descending gradually to continually less refrangibility, we 

 observe that the entire fluorescence-spectrum is excited by all the 

 rays down to 58 — by the ray 58, for example, not merely the por- 

 tion from 30 to 58, but also the more refrangible from 58 to 70. 

 The rays below 58, however, do not excite the yellow-green part 

 of the light of fluorescence (58 to 70), but only the red and orange- 

 coloured part, but this also entirely : for example, if we excite with 

 the ray 48, the fluorescence-spectrum from 30 to 55 is distinctly 

 seen ; light which has passed through three red glasses, and only 

 reaches to 50, excites still very distinctly up to 57. Accordingly 

 the fluorescence- spectrum of anthracene-blue consists of two parts, 

 separated by the minimum at 57, neither of which obeys Stokes's 

 rule, and the second, more refrangible, is excited only by the rays 

 above 57. Anthracene-blue therefore behaves like a mixture of 



