ON ISOMERIC NAPHTHALENE DERIVATIVES. 



175 



peculiar constitution of tbe colouring matters themselves ; the further 

 study of this question, however, has led me to the conclusion that even if 

 the transference could be effected in any other way azo-colours would 

 only result provided that ' quinonoid ' compounds were formed ; at 

 present this is only known to obtain in the case of the 1 : 2 and 1 : 4 

 compounds (cf. 'Chem. Soc. Proceedings,' 1888, p. 27). 



The symhol of naphtlialene. — There appears to be a tendency on the 

 part of some recent investigators of naphthalene derivatives to consider 

 that the naphthalene molecule is dissymmetric. Without discussing this 

 question in detail I would express my conviction that this is not the 

 case, and that the behaviour of naphthalene, and especially its character- 

 istic tendency to form alpha-derivatives, may be satisfactorily expressed 

 by means of a symbol similar to that which I have suggested for benzene 

 (' Phil. Mag.,' Feb. 1887), viz. : 



Kkx> 



Notation of napMlialene derivatives. — Throughout these reports, &c., 

 the system of notation introduced many years ago by the Chemical 

 Society and in ' Watts' Dictionary of Chemistry ' has always been made 

 use of, and its general adoption was advocated in a recent paper by 

 Mr. Wynne and myself (cf. ' Chem. Soc. Proceedings,' 1889, p. 64). It 

 consists in numbering the positions in the one nucleus 1, 2, 3, 4, and the 

 corresponding positions in the second nucleus 1', 2'. 3', 4'. The practice 

 of numbering the positions 1 to 8 appears less desirable and rational in 

 view of the fact that naphthalene consists of two like nuclei, and of the 

 importance of at once being able to recognise which are corresponding 

 positions. In a recent conference at Paris it was, however, resolved to 

 recommend the system of numbering the positions 1 to 8, but this 

 decision appears to have been arrived at without any sufficient discussion 

 of the question or pains being taken to consult those who have the right 

 to express an opinion. The desirability of numbering correspondino- 

 positions similarly in all multinuclear compounds cannot be denied, and 

 it is very easily carried into practice ; thus in the case of anthi-acene the 

 positions in the one lateral nucleus are 1, 2, 3, 4, in the other 1', 2', 3' 4' 

 and in the central nucleus Co, C.j ; in the case of phenanthrene those in 

 the central nucleus are C,, C„ those in the one lateral nucleus 1, 2 3 4 

 those in the other 1', 2', 3', 4'. Thus : ' ' ' 



Vi 



< 



Anthraquinone is a 1 

 3 cen<ri-di-derivative. 



4 cenfrt-di-derivative, phenanthraquinone a 



