96 GIBBS, WILLIAMS, AND PRATT. 
acid colors most rapidly, the ortho only slightly, and the para 
not at all. The esters of the acids color more rapidly than the 
free acids. The para compound is the only one not effected. 
Gentisic acid and its esters —The methyl and ethyl esters of 
gentisic acid color most rapidly of all the compounds studied 
and the free acid is next in order of rapidity. The oxidation of 
the ester by means of other oxidizing agents has been inves- 
tigated. The oxidation of the esters of gentisic acid, salicylic 
acid, and m-hydroxy benzoic acid should produce the same 
compound, the quinone of the ester of benzoic acid. This qui- 
none is undoubtedly produced. It is not obtained in good yields 
and is difficult to purify. The mono-oxime has been prepared. 
This, and other considerations, point to the existence of this 
ester, and that carbon dioxide does not split off at once to produce 
para quinone as has been recorded in the literature. 
We believe that the first and principal colored compound 
formed in every case is a quinone. Later, decompositions and 
condensations are apt to take place. 
