88 GIBBS, WILLIAMS, AND PRATT. 
When a small quantity of an acid is present which has no effect 
on the methy] salicylate, except to increase the rate of hydrolysis, 
such as x sulphuric acid, the stability of the colored compound 
is increased, doubtless by preventing the alkalinity of the solu- 
tion resulting from the absorption of impurities from the glass. 
The above experiments having proved that oxidation in the 
sunlight is the cause of the coloration, and since it has been 
shown * that a similar oxidation may he attributed to hydrogen 
peroxide, the following experiments were devised to determine 
if hydrogen peroxide in the dark would produce similar results. 
A number of tubes were sealed with methyl salicylate, hydro- 
gen peroxide, and other substances as described in Table III, 
kept in the dark and examined from time to time. The hydrogen 
peroxide employed was a 3 per cent solution. 
TABLE III.—The effect of hydrogen peroxide upon methyl salicylate and 
other substances in sealed tubes in the absence of light. Room tem- 
perature about 30°. 
qube Date sealed. 
SS ee = ——__—_—_— 
Date 
- 
examined. | Mixture. Remarks. { 
| 
et Sf | a i | 
ni j 
Sodium carbonate 75 10 cc_ Aqueous layer brown. Ester 
4,191 F 
‘ ae enue | ORS Me A layer colorless. No H2Oz. 
Methyl salicylate 0.5 ce __ 
N 
Sodium carbonate jo Lo cc- Aqueous layer muddy brown. 
| Ester layer colorless. H2Ozdis- 
Oa sro tied tah ard lea pears amare Methyl salicylate 0.5 ce __ 
appeared. 
Hydrogen peroxide 2.0 ce_ 
N 
Sulphuric acid 10 10 cc __ 
| 
| 
i 
| 
| 
Aqueous layer colorless. Ester 
} 
ol peeas Bo aes stra Cota Methyl salicylate 0.5cc -_| ayer yellow, H2Oz present. 
Hydrogen peroxide 2.0 ce_ 
Winter l0feceaesseeeee eens Aqueous layer colorless. Ester 
I eee Goysseeee eee dplae-s=- Methyl salicylate 0.5 cc___| layer brilliant yellow. H2O2 § 
Hydrogen peroxide2.0cc_| present. | 
[eaaeeed 2 = eer eee a= eee 
The yellow compound formed in the tubes, numbers 3 and 4, 
is reduced (decolorized) by sulphurous acid. On shaking with 
dilute alkalies, the color passes from the ester into the water and 
is intensified. This alkaline solution is also decolorized by sul- 
phurous acid. 
A number of tubes containing various amounts of hydrogen 
= Toc. cit. 
