(1) The chemical reactivity of the carboxyl groups of the solid organic acids could be traced comparative-quantitatively by the infrared spectrometric method.
(2) The absorption bands of 1720-1700<cm>^<-1> shown by the alkali-lignins was assigned to the carbonyl stretching vibrations of the carboxyl groups.
(3) The carboxyl groups of alkali-lignin did not give the shift absorption band near 1550<cm>^<-1>, even when neutralized completly by sodium hydroxide solution.
(4) The phenolic absorption bands near 1200<cm>^<-1> of ferulic acid was disappeared by the neutralization, but these phenomena could not be found in the spectrum of the alkali-lignins.
(5) The tracing curves of the neutralization of these solid acids, stearic acid and ferulic acid, as well as, cinnamic acid and lignin carbonic acid were drawn on the smilar lines in these experiments.