NAPHTHA, COAL 395 



psoriasis. M. Emery states that it succeeded in twelve out of fourteen cases. In tho 

 two where it failed the one patient was a woman thirty years of age, who had been 

 afflicted for eight years with psoriasis gyrata; the other patient was a young man 

 who had suffered for several years with lepra vulgaris. In the latter case, two months' 

 treatment having effected no good, pitch ointment was substituted, which effected a 

 cure in two months. The naphthaline was employed in the form of ointment in the 

 strength of ^ or 1 drachm of lard. The application is sometimes, however, attended 

 with severe inflammation of the skin, which must be relieved with poultices. 



The dead oils, as tho less volatile parts of coal-tar are called, contain several sub- 

 stances, the nature of which is very imperfectly known. Among them may be men- 

 tioned pyrene and chrysone. The former has been examined by Laurent, who 

 gives the formula C 30 H'- for it. They are found in tho very last portions that pass in 

 the distillation of coal-tar. They are also said to bo produced during the distillation 

 of fatty or resinous substances. The portions which distil last are in the form of a 

 reddish or yellowish paste, which rapidly darkens in colour on exposure to light. 

 Ether separates it into two portions, one soluble, containing the pyrene, the other 

 insoluble, containing the chrysene. The pyrene may be obtained by exposing the 

 etherial solution to a very low temperature, which will cause it to crystallise out. 

 The composition of pyrene is, according to Laurent, 



Experiment. Calculation. 



Carbon . . . 93-18 , C so 937 



Hydrogen . 6'11 . . H" 6-3 



99-29 100-0 



The portion insoluble in ether consists of chrysene in a tolerably pure state. 

 G. Williams found that it crystallises on cooling from a solution in Boghead naphtha, 

 in magnificent yellow plates, with a superb lustre resembling crystallised iodide of 

 lead. The following are the results of its analysis. His combustion was made upon 

 chrysene crystallised as above : 



Laurent. C. Gr. W. Calculation 



Carbon . . 94-83 94'25 94'63 9474 C 18 108 



Hydrogen . 6'44 5'30 5'37 5'26 H 8 6 



100-27 99-55 lOO'OO 100-00 114 



See CHRYSENE, 



No commercial use has been yet devised for these interesting bodies ; which are also 

 bye-products in paraffin refineries. But the brilliant discoveries of Graebe and 

 Lieberman have raised anthracene from the category of waste materials. In 1868 they 

 obtained anthracene from alizarine, and in the following year they were able to disclose 

 a process for the manufacture of the valuable dye from the unsavoury coal-tar product. 

 A large extension of the coal-tar colour manufacture has ensued. Anthracene is ob- 

 tained from the heavier coal oils, which when exposed to the action of a powerful 

 freezing mixture, often deposit a mass of crystals only partly soluble in alcohol. The 

 soluble portion consists of naphthaline ; the other portion is anthracene, or para- 

 naphthaline. It appears, from the analyses which have been made, to be isomeric 

 with naphthaline. It fuses at 356, and boils at about 580. The density of its 

 vapour, determined at 848, was 6-741, agreeing very well with the formula C 30 H 12 , 

 which requires 6 - 643. This formula is one and a half times naphthaline, thus: 

 C 20 H 8 + C l H 4 = C'H 12 . For a description of the methods by which anthracene is now 

 prepared from coal-tar, and alizarene from anthracene, the reader is referred to these 

 articles respectively, and to the Supplement to Watts' s ' Dictionary of Chemistry.' 



Metanaphthaline is a peculiar substance which appears to be closely related to the 

 above products. It is formed during the manufacture of resin gas. It is a fatty sub- 

 stance fusing at 158, and distilling at about 617 ; it is at present but little known. 



The following Table, taken from Traite des Derives de la Houille, by Gerard and 

 De Laire, epitomises the operations of French tar-distillers : 



FIEST DISTILLATION OF COAL IN THE KETOBTS. 

 Gas. Tar. Coke. 



SECOND DISTILLATION OF THE TAB. 



1. Light oils (boiling 30 to 150 Cent.). 2. Medium or creasote oils (boiling 

 140 to 200 Cent.). 3. Anthracene oils, or heavy oils, containing naphthaline 

 and anthracene (boiling 200 to 350 Cent.). 



