Colour and Chemical Constitution. 
207 
has a value of 98. All other parts of a molecule have small values : any 
group attached to the inner end of a tautomerism and itself incapable of 
tautomerism has a value of about 7i, viz. 7 for small groups, e. g. Me, Et, 
CI, and 8 for large groups such as iodine or phenyl. G-roups of the above 
kind, but attached to the middle of the tautomerism, have double value, 
viz. about 15 (14 for methyl, 16 for iodine or phenyl). An anomaly may 
be noted, namely that groups on the final nitrogen of tautomerism 3 have 
this double value also, the tautomerism 
having the value of 126 (viz. 98 + (2 x 14)). 
Now in a colour containing a phenol-ring, the folloAving dissection of 
the ring is to be imagined : 
The part on the left within the thick lines is the CCO tautomerism loaded 
with a non-tautomeric group CH in the middle ; its value is therefore 94 + 
15 = 109. The next tautomerism is CCC loaded with a group CH (rest of 
benzene- ring), this time at its end ; its value is thus 103 + 7 = 110. The 
CH in the square of the diagram is common to both tautomerisms. The 
total value of the phenol-ring is thus 219, and this is CCO + CCC + 22. Thus 
the non-tautomeric portion of the benzene-ring — CH = CH — has always 
a value of 22. 
In the same way the value of the aniline or para-aminophenyl-ring is 
CCN -\- CCC + 22 - 223; and the value of the para-dimethylaminophenyl- 
ring is 126 -f 103 + 22 = 251. 
Any halogenated phenol-ring will have the value 219 + 7 = 226 if the 
halogen is ortho to the hydroxy 1, and the value 219 + 15 = 234 if the halogen 
is meta, the one being a terminal and the other a central loading of the 
tautomerism (if the substituent is large, viz. iodine, the value is one or two 
more). Alkyl derivatives have the same values, viz. 7 or 15, if attached to 
carbon. 
Similarly halogenated aniline-rings have the values 223 + 7 = 230 if 
ortho, and 223 + 15 = 238 if meta, and so on, all the substituents having 
nearly the same value if non-tautomeric, and everything being additive. 
Examples will be given later on in the paper. A few concrete cases may 
now be studied : 
(1) Dioxyhenzhydrol {aqueous alliali). 
The formula is 
Me^N - CH = C( 
O \= CH ^_0' 
