CARBOHYDRATES 61 



reported (compare with amylose, p. 50). Probably the higher figures arc 

 more nearly correct for intact cellulose as it actually exists in plants. 



The woody and fibrous tissues which provide strength and rigidity for 

 plants, as bones do for animals, are composed of a mixture of cellulose 

 with several other polysaccharides [hemicelluloses and cellulosans) and a 

 noncarbohydrate material, lignin. Cotton fibers are an exception to this 

 statement since they consist of practically pure cellulose (over 98 per 

 cent) . 



From an industrial and economic standpoint cellulose is the most im- 

 portant of all the carbohydrates (see Table 3-1, p. 20). Cotton and 

 linen goods, rayon, paper and pulp products, rope, twine, and other cordage 

 materials are composed almost entirely of cellulose. The largest single 

 source is wood, cither in its natural form or in the form of paper and pulp 

 products. Wood contains, on the dry basis, about 60-70 per cent of 

 carbohydrates and 20-30 per cent of lignin. About half of the carbo- 

 hydrate fraction consists of true cellulose. The process of paper-making 

 is essentially a matter of separating the cellulose from the lignin, hemi- 

 cellulose, and other constituents of wood. Pressure-cooking the wood, 

 in the form of chips, at 130-175°C., with water containing such chemicals 

 as calcium bisulfite plus sulfur dioxide (sulfite process) or sodium hy- 

 droxide plus sodium sulfide (Kraft process) , dissolves the lignin and most 

 of the hemicelluloses. The insoluble fiber or "pulp," consisting of most 

 of the cellulose plus smaller amounts of other resistant polysaccharides, is 

 separated from the water solution, called "waste liquor," and either rolled 

 into sheets to make paper or used as a source of crude cellulose for other 

 industrial purposes (see below). During the years 1947-1950 wood pulp 

 was produced in the United States at the rate of about 12,000,000 to 

 15,000,000 tons annually. 



Disposal of the enormous quantities of waste liquors, produced as a 

 by-product of the pulp and paper industry, is still an unsolved challenge 

 to chemists. The sugars present can be fermented to produce alcohol, 

 lactic acid, or yeast, but only a small portion of the total is so utilized. 

 Heating with strong alkali converts 10 to 20 per cent of the lignin into 

 vanillin, a component of vanilla. Unfortunately the use of vanillin for 

 flavoring offers a market for only a tiny fraction of the lignin available. 



CHO 



Mercerized cloth, named after John Mercer who originated the process, 

 is obtained by treating cotton cloth with alkali and subsequently washing 

 and drying the cloth. The individual fibers become thicker and shorter. 



