Colour and Cliemiral Co7isfitufion. 
211 
(Micliler-hydrol). The observed wave-lengths are AA.578 and 608 respec- 
tively. Oxydimethylaminobenzhydrol has not yet been observed, but its 
calculated wave-length is 219 + 103 + 251, or 573. Its phenyl derivative 
(dimethylaminofuchsone of Part X) has been observed, giving A 586, whence 
oxydimethylaminobenzhydrol itself should have X = 586 minus 16 or 570. 
Taking the unknown, therefore, to have wave-length 571, and remembering 
that Michler-hydrol has X 603, we see that the two colours of paraoxymala- 
chite-green (bis-dimethylamino-fuchsone) are both about 6 units higher than 
those of the simple benzliydrol compounds, this being the allowance for the 
non-tautomeric group or load, C^.H_,NMeo or C^HjOH respectively. The 
theory, therefore, not only accounts for two colours in this substance, but 
enables them to l)e calculated. 
(15) MichJer's l-etone (salt in water). 
The formula is 
^in 
The substance is yellow, and there are only three tautomerisms, as shown in 
the formula. The tautomerising ring CgHjNMe.j has been shown to have 
the value 251 ; adding the tautomerism CCO of value 94 and 16 for the 
benzene-ring load (non-tautomeric) we get 361 as the calculated wave-length. 
The observed figure is about X 364 ( X 368 in alcohol, Watson, p. 88). The 
small difference is due to the load on the benzene-ring outside the tauto- 
merism. In previous paragraphs (substances 13 and 14) it is shown that 
substitution in the benzene-ring outside the tautomerism causes small but 
variable changes in the value (16) assigned to plain phenyl. These small 
differences are at present anomalous but do not much affect the validity of 
the theory. In this particular case, too, one may note that the tautomerism 
\c 
/ 
may be of lower value tliau the simple tautomerism CCO on the analogy of 
the tautomerism 
in which case the calculated value would be about seven units loAver, 
An explanation is still required for the marked yellow colour of the dye 
auramine, which is derived from Michler's ketone by replacement of O by 
