The solubility of the acid lignins polymerized by strong acids are very low. On the other hand, according to the results of these experiments, a part or major part of the technical acid lignins are able to be maked soluble to the dilute alkaline aqueous solution of the concentrations under 6 %, when treated at 165-160℃, 2 hours.
From the solutions of the lignins are fractionated α-, β-, and γ-fractions by neutralization with dilute sulfuric acid (pH. 3), and the yields of these fractions are obtained about 50%, 25%, and 25% respectively by treatments under the given conditions.
However, some problems about the behaviours of the other acid lignins preparated by different processes will be discussed at following studies.