The researches on the reactivity of the functional groups of several solid organic acids has been continued.
(1) As the monomers of the lignin carboxylic acids, the vanillic acid and the hydrocinnamic acid were investigated by the infra-red spectrometric method.
(2) The shift waves and intensity decrements of the absorption bands of β-alkali lignin near 1710 <cm>^<-1>, when neutralized with sodium hydroxide solution, were qualitatively and quantitatively considered comparing with those of the cinnamic acid and the ferulic acid. Then it was confirmed that these absorption bands showed the existence of the carboxylic acids contained in these lignins.
(3) The neutralizations of the β-alkali lignin carbxylic acids gave more imformations concerning the IR spectra than those of the alkali lignin reported previously.
(4) The curves of the neutralization of the β-alkali lignin was matched with that of the cinnamic acid, but not with the ferulic acid. These tendencies were quite same with the results of the alkalilignins reported in the previous paper(1).