80 GIBBS, WILLIAMS, AND PRATT. 
of carbon dioxide by methyl salicylate, described later in Part 1V.* 
This work proved that no carbon dioxide was separated from 
methyl salicylate in acid solution, even at boiling temperature, 
while, during the hydrolysis in alkaline solution, small quantities 
of carbon dioxide were split off, but these were negligible in the 
work at hand. 
The next investigation concerned itself with the possible for- 
mation of colored compounds of the nature of formaldehyde 
condensation products, since it was shown that the methyl 
alcohol, formed by the hydrolysis of the ester in acid or alkaline 
solution, was partially oxidized to formaldehyde® and it is well 
known that aldehydes condense with phenols and quinones form- 
ing a variety of colored compounds usually described as yellow 
or red. 
While it is possible that small quantities of aldehyde-phenol, 
or -quinone, condensation products are formed after long ex- 
posure to the action of light, the first colored compounds formed 
and the principal cause of the coloration is not traceable to 
reactions of this nature. The fact that a light yellow color is 
produced in tubes containing only methyl salicylate, after an 
exposure of one hour to the sunlight, is proof of this statement. 
Even though traces of water might be present, the hydrolysis, 
producing methyl alcohol, would not have progressed sufficiently 
to permit of the formation of any quantities of formaldehyde 
which need be considered in this’ connection. Moreover, an 
inspection of the results obtained with the tubes described in 
Tables V and VI will show that the presence of any considerable 
amounts of formaldehyde will delay the color formation and 
reduce its intensity, probably because formaldehyde itself is more 
easily oxidized than methyl salicylate. Furthermore, both 
salicylic acid and its methyl ester are oxidized with the forma- 
tion of yellow or red compounds (depending upon the conditions) 
by hydrogen peroxide, the latter more easily than the former, the 
possibility of formaldehyde condensation products being the 
principal cause of the color is again excluded. . 
The coloration of methyl salicylate requires the presence of 
oxygen and light, or an oxidizing agent in the dark. In the 
“To follow. : 
*The oxidation of methyl alcohol under the influence of, (a) sunlight, 
and, (b) hydrogen peroxide. See preceding paper, page 57. 
°*Eder, Photochemie. Halle a. S. (1906), 350. The oxidation of formal- 
dehyde to formic acid can be brought about and the rate increased by 
sunlight. 
