Hydrocarbons found in Coal-tar and Petroleum Distillates. 347 



Fluorescent Spectrum of Solution. — When impure anthracene 

 in the fourth condition is dissolved in benzole, it gives a bright- 

 yellow solution fluorescing strongly with a light which appears 

 green and yields, on analysis, a spectrum which closely resembles 

 that of the solid, having, however, all its bands displaced towards 



the more refrangible end. 



This is shown in %. 4. 



Spectrum of Chrysogen in Solution. — But I ought to say that 

 in this, and also the preceding spectrum, the band at 6'1 of the 

 scale here and 4° 7 in the other, is represented in the engraving 

 as too strong and broad, being in fact fainter and narrower than 

 the other bands. 



This displacement of fluorescent bands by solution finds a pa- 

 rallel in the case of a substance first observed by me in some 

 petroleum-residues many months since (see ^Proceedings of 

 Franklin Institute,^ vol. Ixiii. p. 296). This gives a fluorescent 

 spectrum having a close relation to that of chrysogen, and, like 

 it, showing a displacement upwards by solutions difi'ering with 

 the solvent. 



Hagenbach, in his last paper, which has just reached me in 

 due course of post (see Poggendorff^s ^7^/^«/e/^, 1872), announces 

 that he has just observed a displacement of maxima in the fluo- 

 rescent spectrum of some solutions by a change in the solvent. 



Absorption-spectrum of Chrysogen. — When the same impure 

 anthracene (4), if spread thinly on paper or mixed with pa- 

 raffine, is spread on glass, or is fused between slips of mica, 

 and is then viewed by transmitted blue light in the manner 

 shown in fig. 5, we obtain a marked absorption-spectrum which 



Fig. 5. 



A is the port-lumiere with a diaphragm at B, C is a tank containing a so- 

 lution of ammonio-sulphate of copi)ei', D an adjustable table carjying 

 the solid or solution to be examined, and E a Browning one-prism 

 spectroscope. 



