The writer has separated raw hydrosulphide lignin from waste liquor. After refining, he has made a full study of this lignin, having pointed out a few characteristics in comparison with the ordinary SP lignin as follows :
1) increase of SH group, i. e., the lignin purified contains more sulphur and it is this acid group that acidifies the lignin,
2) decrease of MeO group, i. e., CH₃O group in this lignin are reduced to half those of other lignin delivatives.