[en] In the previous paper, benzyl ethyl ether lignin (BEEL) and 2, 2-dimethoxypropane lignin (DMPL) were prepared by solvolysis of ¹⁴C, ³H-double labelled MWL and their structural changes of the phenylpropane unit during the isolation procedure were studied. In this paper, BEEL, DMPL, ethanolysis lignin, dioxane lignin and Klason lignin were prepared from ¹⁴C, ³H-double labelled wood meal, in which each carbon of the phenylpropane unit and the hydrogen at the position 2 of the aromatic ring in lignin were labelled with ¹⁴C and ³H respectively. The structural changes during the isolation procedure were investigated on each lignin preparation from the changes of ¹⁴C/³H ratio. It can be considered that the changes of the ratio indicate the changes of the number of the carbon atoms on each labelled position per aromatic nucleus. The structural changes of BEEL and DMPL were shown to be much less that those of the lignin dissolved in the control experiment in which wood meal was treated in anhydrous dioxane containing 0.5 M HCl. The structural changes of ethanolysis lignin were also as little as those of BEEL or DMPL. Appreciable cleavage of methoxyl groups was observed in dioxane lignin prepared by treating wood meal in dioxane-water containing a small amount of hydrochloric acid at 100⁰C for 8 hours. In Klason lignin, near the half of ³H on the aromatic ring and a certain amount of γ-carbons and methoxyl groups were lost as an acid soluble fraction. (auth.)