346 Dr. H. Morton on the Flum-escent Relations of certain 



Trans. 1852, Part II. p. 469), and also used by Becquerel (see 

 La Lumiere, vol. i. p. 335, and Comptes Rendus, vol. Ixxv. 

 p. 297), as also by Hagenbach. Figure 2 hardly needs 

 any explanation, except that A Fig- 2. 



is a porte-lumiere with a lens 

 at B, and a small tank of ammo- 

 nio-cupric sulphate in front, C a 

 revolving stand to hold objects, 

 and D a spectroscope. 



Observations on the Fluorescent 

 Spectrum. — All the forms of an- 

 thracene except the last show, 

 when observed as above, the same 

 spectrum, which seems to me also 

 to correspond as nearly as one 

 would expect with the drawing given by Becquerel (in La Lumiere) 

 of a hydrocarbon having the colour of the uranium salts and ob- 

 tained from Fritzsche, w^ho first investigated what we now call 

 anthracene. This spectrum is shown in fig. 3. 



Fig. 3. 



]- 



B C 



Spectrum of Lnpure Anthracene referred to Bunsen's Scale. — 

 The anthracene described above as the sixth variety, however, 

 shows a fainter fluorescence and gives a continuous spectrum. 

 It yields, however, with the various solvents and chemical tests, 

 abundant evidence that it is not para-anthracene, but simply a 

 perfectly pure condition of anthracene itself. 



It would thus appear that some part of the brilliant blue fluo- 

 rescence ascribed to anthracene may have been due, as was 

 beyond doubt the spectrum figured by Becquerel and also the 

 one measured by Hagenbach, to an adherent impurity. 



Cause of Fluorescence and of the Banded Spectrum of Commer- 

 cial Anthracene. — A series of experiments make it clear that the 

 yellow body persistently adhering to anthracene and soluble in 

 ether, benzole, and carbon-bisulphide, as described by Fritzsche 

 under the name chrysogen, was the substance in question. It is 

 most abundant, and free from interfering substances, in the 

 fourth sort of anthracene ; for it seems to be practically inso- 

 luble in alcohol, the brown or yellow matter take up by that 

 fluid being quite a different substance. 



