摘要：ABSTRACT: The hemicelluloses are the principle non-cellulosic polysaccharides present in wood. Hemicellulose and cellulose collectively make the holocellulose of the wood. Hemicelluloses are distinguished from cellulose by the property that they are soluble in dilute aqueous alkali and in boiling water. After separation from the other wood components these are hydrolysed by warm and dilute acids into simple pentose or hexose sugars. Xylan, araban, mannan and galactan, as the name imply; on hydrolysis each one gives xylose, arabinose, mannose and galactose respectively. A hemicellulose giving both galactose and arabinose is a galacto-araban. The hemicelluloses are completely soluble in dilute caustic alkalis. A cold or hot 5% solution of sodium hydroxide is usually employed for their extraction. Isolated hemicelluloses are also soluble in hot, saturated solution of sodium carbonate and pentosans are removed from wood pulp by heating it with magnesium sulphite in the presence of calcium or magnesium oxide. Keywords: Hemicellulose, holocellulose, hexose, pentose and wood pulp.
