vin, a, i Gibbs and Pratt: Hydroxyl and Carboxyl 43 



while the latter may be an ionization phenomenon. Baly and 

 Schaefer 17 have pointed out from a study of cinnamylideneacetic, 

 cinnamylidenemalonic, and other acids that the addition of alkali 

 decreases, while the addition of acids increases, the free affinity 

 of the carbonyl group, and state that the natural deduction 

 from this is that the more the substance is ionized the less the 

 free affinity possessed by the carbonyl group. 



The amount of free affinity of the carbonyl group is greatest when the 

 acid is not ionized and least in the easily ionized sodium salt. 



The absorption curve of the methyl ether of methyl salicylate 

 is neither shifted nor altered in any way in the presence of alkali. 

 This behavior is to be expected from a nonionizable compound 

 of this type. 



It is interesting to note that the absorption bands heading at 

 1/A=3440 of phenol, o-cresol, and of o-hydroxybenzyl alcohol, 

 all in presence of 5 equivalents of alkali, almost coincide with 

 that of the methyl ether of salicylic acid in neutral solution and 

 of the methyl ether of methyl salicylate, and further that these 

 5 curves all show an incipient band in the benzene region. It 

 is evident that under these conditions the internal molecular 

 vibrations of these compounds are remarkably similar. In 

 phenol, o-cresol, and o-hydroxybenzyl alcohol, the enol-keto 

 tautomerism exists without the modifying influence of the car- 

 bonyl group, and the absorption curves of these three compounds 

 and of their methyl ethers are almost identical. The replacement 

 of the hydroxylic hydrogen atom of these compounds by sodium 

 is thus seen to produce much the same effect as the adjacent 

 carbonyl group produces in their ethers. 



SALICYLIC ACID AND METHYL SALICYLATE. FIG. 4 



The absorption spectra of these compounds have been de- 

 scribed by Hartley and Huntington 18 and Hartley, 19 but, for 

 purposes of comparison with the other compounds described in 

 this paper, we have photographed salicylic acid in alcohol, and 

 its methyl ester 20 in neutral water and in alcohol solutions, 



17 Joum. Chem. Soc. London (1908), 93, 1808. 



18 Loc. cit. 



19 Joum. Chem. Soc. London (1888), 53, 641. 



20 Methyl salicylate was photographed in absolute alcohol solutions, and 

 in aqueous solutions which contained sufficient alcohol to complete the 

 solution. One-tenth molar solutions were made in 50 per cent alcohol, 

 one-hundredth in 35 per cent alcohol, and one-thousand in 3.5 per cent 

 alcohol. 



