METHYL SALICYLATE III. 93 
TABLE VII.—The action of sunlight, etc——Continued. 
Tube Condition on 
No. Coutents of tube. February 13, 1912. Remarks. 
18C | Same as last, no CCla_________ Golorless:==- +202 -6- 2-8 22-5 
Quinol carboxylic acid 0.2 
TAM os et Aqueous layer red. ___________ 
Water) > \CCl2s2= 2 cso o een ne CCla colorless ____.-__--_------ 
Carbon tetrachloride 2 ec__-__- 
3C 
4C | Same as last, no CCl4 __-_-_-- 
Methyl ester of quinol car- | Aqueous layer and CCl4 ! Of all the tubes tabulated 
ic boxylic acid 0.2 gram_-_____- layer equally colored red. here, this one colored 
Water 5 cc __---.-----=------- Deposit of dark red resi- most rapidly. Deep yel- 
Carbon tetrachloride 2 ce_____ nous substance ______-__-__- low in 10 minutes. 
2C | Same as last, no CCl4 ________ 
20C | O-cresol ___------------------- 
Colored in 1 day. 
First of the cresols to co- 
BIG || MASEL) cence cecsesgtsesssece DESO YON sssesessesstssesas lor. Visible in 1 hour. 
Dirhtyellows--e sea Colored in 1 day. 
51C | P-cresol 
52C | Methyl ether of p-cresol-____-- Golorless 222222 23.2ke eee 
The cresols in tubes numbered 20 C, 50 C, and 51 C were all 
pure and freshly distilled. Practically no moisture was present 
in the tubes. 
QUINOL CARBOXYLIC ACID (GENTISIC ACID). 
The esters of this compound are the most rapidly effected by 
sunlight and oxygen of all of the compounds studied. Prelimi- 
nary studies of the oxidation of the methyl ester (colorless, crys- 
talline compound, melting point 85°.8 corrected) for the purpose 
of preparing the corresponding quinone, show that the oxidation 
is easily effected in the cold by hydrogen peroxide, very dilute 
solutions of potassium dichromate and dilute sulphuric acid, very 
dilute solutions of potassium persulphate and dilute sulphuric 
acid, and other oxidizing agents. Potassium persulphate with 
dilute sulphuric acid seems to produce the best result although 
it is very difficult, in all cases, to carry the reaction to completion 
