90 Dr. H. Morton on the Fluorescent Relations of certain 



John Truax, of Pittsburgh, who has been most obliging in fur- 

 nishing me with every facility that could be wished. 



The preliminary history of the material with which we have 

 to work is as follows : — 



When the residues left in the distillation of petroleum for the 

 manufacture of illuminating-oils are redistilled to obtain lubri- 

 cating-oils and paraffine, there passes over near the end of the 

 operation, and when the still is at the bottom almost or even 

 quite red-hot, a thick resinous matter of a dark honey- or light 

 sepia-colour, which is used as a lubricant for the necks of 

 " rolls " in iron mills. This is the material from which the new 

 body is extracted by the following process. 



The tarry matter above described is mixed with about its own 

 volume of benzine (petroleum-naphtha), and is thrown on a stout 

 filter, where it is well washed with the same solvent. 



This leaves a dark olive-green flaky powder, constituting 

 about 3 per cent, of the original mass, and very similar in ap- 

 pearance to crude commercial anthracene. We now wash this 

 with alcohol, and even digest it in this liquid, by which means a 

 brown material, whose solution in alcohol has a decided blue 

 fluorescence, is removed. 



The substance is then dissolved in hot benzole (coal-tar 

 naphtha) and filtered in a jacketed funnel (by which operation a 

 quantity of black powder is removed), and is allowed to crystal- 

 lize on cooling. 



It then deposits in very small acicular crystals collecting in 

 tufts ; and the purification is carried on by re-solution and crys- 

 tallization from fresh benzole. The substance then has the 

 colour of potassium chromate. 



The following Table of solubilities will indicate the motive for 

 the above treatment. 



Benzine, hot (160° F.), dissolves 1 part in 1155 

 cold (70° F.) „ „ 2900 



Alcohol, hot (160° F.) „ „ 4172 



cold (70° F.) „ „ 16625 



Benzole, hot (160° F.) „ „ 95 



cold (70° F.) „ „ 152 



This substance dissolves in turpentine pretty freely, and yet 

 more so in carbon-bisulphide and chloroform. 



In ether and olive-oil and carbon-bichloride it is hardly as 

 soluble as in benzine. 



Methods of Examination. 

 For the study of the spectrum of the fluorescent light, the 



