## 3 Results and Discussion
### Chemical Composition
The results of the extractive content are shown in Table 5. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Treatment** & **Alpha-Cellulose (\%)** & **Hemicelluloses (\%)** & **Insoluble Lignin (\%)** & **Soluble Lignin (\%)** & **Total Lignin (\%)** \\ \hline \multirow{2}{*}{Untreated} & 48.21 AB & 24.24 a & 32.34 A & 1.89 a & 34.23 A \\ \cline{2-6}  & (0.74) & (2.10) & (2.48) & (0.45) & (2.34) \\ \hline \multirow{2}{*}{CS160} & 53.01 A & 8.89 c & 33.36 A & 1.61 b & 34.97 A \\ \cline{2-6}  & (4.15) & (6.36) & (9.76) & (5.40) & (9.57) \\ \hline \multirow{2}{*}{OS185} & 46.04 AB & 24.55 a & 32.29 A & 1.88 a & 34.17 A \\ \cline{2-6}  & (0.27) & (1.57) & (0.52) & (2.32) & (0.42) \\ \hline \multirow{2}{*}{OS210} & 45.72 B & 21.20 b & 33.554A & 1.72 b & 35.27 A \\ \cline{2-6}  & (0.59) & (4.93) & (1.26) & (3.32) & (1.32) \\ \hline \multirow{2}{*}{Shapiro-Wilk test} & 0.0065 \({}^{\star}\) & 0.41 ns & 0.0356 \({}^{\star}\) & 0.8384 ns & 0.0359 \({}^{\star}\) \\ \hline \multirow{2}{*}{Barlett test} & 0.0034 \({}^{\star}\) & 0.59 ns & 0.0058 \({}^{\star}\) & 0.0642 ns & 0.0046 \({}^{\star}\) \\ \hline \multicolumn{2}{c}{F-test} & - & 239.3 \({}^{\star}\) & - & 14.94 \({}^{\star}\) & - \\ \hline \multicolumn{2}{c}{H-test} & 9.84 & - & 3.20 & - & 3.21 \\ \hline \multicolumn{2}{c}{r} & 0.909 ns & \multicolumn{1}{c}{\(-\)0.996 \({}^{\star}\)} & 0.580 ns & \multicolumn{1}{c}{\(-\)0.880 ns} & 0.487 ns \\ \hline \end{tabular}  
* Means followed by the same lowercase or uppercase letter in the columns do not differ (\(p<0.05\)) according to the Tukey and Bonferroni tests, respectively. ns: not significant (\(p>0.05\)). *: significant (\(p<0.05\)). Results in parentheses are the coefficient of variation (%).  
\end{table} 
Table 4: Mean results of structural components of wood per treatment. CS160 had the highest total extractive content, while the open-system treatments (OS185 and OS210) had means closer to the untreated wood, although all means differed significantly from each other. The extraction performed with the sequence ethanol:toluene, ethanol, and hot water, accounted for as total extractives, showed the highest absolute means compared to the other solvents. This sequential extraction uses a mixture of solvents, allowing the removal of several classes of extractives with different molecular weights [23]. Indeed, CS160 had the highest means of extractive content of all tested solvents. There was a strong, positive, and significant correlation between CML and total extractive content (r = 0.994 *) indicating an increase in extractives with mass loss. The higher mass loss, associated with the impossibility of the removal of gases from the equipment, resulted in a higher amount of extractives in the closed-system than in the open-system processes. The open-system treatments (OS185 and OS210) showed different trends compared to untreated wood in terms of extractives in acetone and dichloromethane. For extractives in acetone, OS185 had a mean similar to the untreated, while the mean of OS210 was twofold that of the untreated. For extractives in dichloromethane, OS210 had a mean similar to that of the untreated, while OS185 had a mean of less than half of it. In the acetone extraction process, it is suggested that 185 \({}^{\circ}\)C was not sufficient to volatilize the polar extractives, while 210 \({}^{\circ}\)C increased the extractive content due to mass loss. On the other hand, in dichloromethane extraction, 185 \({}^{\circ}\)C was sufficient to volatilize the non-polar extractives, while 210 \({}^{\circ}\)C produced new substances that compensated for the volatilized fraction. The trend observed in the extraction with dichloromethane is in line with the literature for open-system processes [3; 35]. The extractive content of thermally modified wood can vary compared to untreated wood, increasing or reducing depending on the process type and schedule (time, temperature), which affect the chemical reactions during thermal modification, forming different types of substances.