the hemicelluloses of deciduous woods are readily hyydrolysed into monomeric sugars, acetic acid and the other components by steam at 185ํc,as in prehydrolysed kraft pulping or in autohydrolysis,or at lower temperatures by mild acids.In contrast the hemicellulose of coniferous woods are not depolymerized in autohydrolysis,but require an acid catalyst for hydrolysis. An effective acid catalyst for this purpose is SO2