372 GIBBS AND PRATT. 
in the absorption band of phenol which occurs on the addition of 
alkalies. They state as a result of a reéxamination of the spectra 
of these compounds: 
We feel therefore that the chain of evidence against there being any 
radical difference between the structure of the nitrophenols and their 
sodium salts is completed by these observations and therefore are bound 
to express ourselves against the quinoid configuration of the nitroanilines 
and the sodium nitrophenoxides. 
We have examined the absorption spectra of p-nitrophenol, o- 
nitrophenol and -nitrosophenol in absolute alcohol, and believe 
that our evidence is conclusive in favor of the quinoid representa- 
tion for these compounds in alkaline solution and that a chemical 
equilibrum exists between the benzenoid and the quinoid forms 
the position of which depends upon the concentration of the 
alkali or acid. When sufficient quantity of sodium ethoxide 
is present in the alcohol solutions, the compounds are completely, 
or almost completely, in the quinoid form, and in the presence 
of a sufficient concentration of acid the reverse is the case. Our 
evidence on this point has been obtained by a simple method 
which Baly and his coworkers have overlooked. 
In the investigation of the phthaloximes * we were impressed 
by the facts that in alkaline solution these compounds give a 
color band which is entirely lacking in the absence of alkalies, 
that this band falls in the region of the quinone color band, and 
is, in many respects, identical with the color band of the nitro- 
anilines, the salts of the nitrophenols, and of p-nitrosophenol; 
and, moreover, the persistence of the color band, and consequent 
depth of the color of the compound, depends exclusively, up to 
certain limits, upon the concentration of the alkali. Moreover, 
no appreciable horizontal shift in the position of the head of the 
band was observable with different concentrations of alkalies, the 
effect of increasing concentration of alkali being merely to 
increase the breadth and persistence of the band. Believing that 
the effect of alkalies was the production of a new form of 
isorropesis which was not present in the criginal substance, we 
were lead to the examination of nitrophenols and p-nitrosophenol 
in an analogous manner, since Baly and his coworkers had 
always employed, as we gathered from their papers, a concen- 
tration of alkali equal to, or in excess of, that required to convert 
*To appear. 
a Ss le ee ee 
