﻿Organic Substances and the Electron Theory. 201 



Since, as has been said, m is larger than m m or m p , it 

 follows that there is a diminution of the induction coefficient 

 and a reduction of tan 97, i. e. an increase of the friction 

 coefficient in the series. The bands therefore gradually be- 

 come more diffuse on passing towards the extreme ultraviolet, 

 while the first may be expected to be exceptionally sharp. 

 This it in fact is, for it breaks up even in solution, giving 



the seven well-known benzene bands described by Hartley, 



4, 5, 11 * 



Only the a 4 and (3 7 series of! bands have been actually 

 observed ; the constants have been calculated from these, 

 and it was then found that the 7 and h series are out of 

 range of all the present spectroscopes. 



Non-symmetrical ring systems (toluene, pyridine, &c). — 

 The complete investigation of these cases need not be given. 

 They are, in general, too complex for treatment, but in any 

 particular case can be worked out numerically when the 

 requisite data are available. It appears that the bands will 

 be of the same general character as the benzene system, but 

 the double bands ft and 7 will separate into their com- 

 ponents t- These, however, will probably not be sufficiently 

 far apart to be distinct, so the total effect will be a single 

 broad band. 



Also the band corresponding to a. will become less sharp 

 as the departure from symmetry becomes more and more 

 pronounced. 



VI. A benzene nucleus with an independent oscillation 

 centre outside it. 



We must assume that the coefficients of the benzene 

 system are unaltered by the presence of the new centre. 



The coefficients for this are denoted by X, sr, fi , /i nn yu v . 



This case also is too complex for general treatment. No 

 reasons can be given for assuming that the benzene group in 

 general acts like the single centre of § II. or the simple group 

 of § IV. 



* It may be stated as a general principle that the "nearest" band is 

 the one most likely to break up into small bands, and this is most likely 

 to happen when the frequency and characteristic equation break np into 

 factors. 



In addition, the substance in question must be fairly volatile, since 

 bands always tend to coalesce as the temperature increases. 



I In the monosubstituted derivatives, and in pyridine, it appears that 

 one component each of the fi and y bands is altogether unchanged. A 

 similar result is obtained when an independent oscillation centre is 

 introduced into the molecule, and also in the case of quinone. diphenyl. 

 diphenylmethane, &c. 



