376 GIBBS AND PRATT. 
P-nitrosophenol in neutral, acid, and alkaline solutions shows 
equally striking results which are parallel in every respect to 
p-nitrophenol and indicate the chemical equilibrium which is 
customarily represented by the equation: 
OH O 
yn Baa 
f cr Cy 
: ie 
N=O N.OH. 
Our chart of the absorption curve of this compound (fig. 2) 
agrees with that of Baly, Edwards, and Stewart ® and, had they 
photographed the compound in the presence of less than one 
equivalent of alkali it would have been evident that the band 
heading at 410 py is not due to a shift of over 110 pp of the band 
heading about 300 py, a shift in position which is in all probability 
impossible without a complete change in the character of the 
dynamic isomerism. In the presence of traces of hydrogen 
chloride, the general absorption in the visible spectrum is some- 
what reduced while the remainder of the curve and the band 
heading at 300 pu are not affected. The changes in the full curve 
(fig. 2) are so slight that the effect of traces of acid is not shown 
in the chart. 
In o-nitrophenol ” it is quite evident, from a study of the chart 
showing the curves of the absorption spectra (fig. 3), that the 
isorropesis is somewhat different from that found in the two 
preceding compounds and the band heading at 270 pp is charac- 
teristic of this condition. The band heading at 345 yp disappears 
progressively on the addition of alkalies, while a new band head- 
ing at about 420 pp makes its appearance. The band at 270 pp is 
also altered by the addition of alkalies, but to a much lesser degree 
than the other two bands. The curve of the absorption spectrum 
obtained with traces of hydrogen chloride is only slightly modified 
when the solution is saturated with this gas and it has been 
deemed unnecessary to plot this change upon the chart. The 
effect of high concentrations of hydrogen chloride is most ap- 
parent in the transmission band heading at 309 uy, the persist- 
*Tbid., fig. 7, p. 522. 
“Armstrong [Proc. Chem. Soc., London (1892), 101] suggested the 
quinoid formula for the o- and p-nitrophenols and proposed the name 
quinone ortho nitroxime for o-nitrophenol. 
