Substances accompanying cellulose

In the sulphite pulping process wood cut into pieces is subjected to kiering in a calcium bisulphite solution under a pressure of 3-8 kg/cm2, at 120-145°C for 7-30 hr. The higher the temperature, the shorter the time of boiling. Substances accompanying cellulose dissolve in the liquor. Lignin is converted into a soluble lignin sulphonic acid. Cellulose is isolated from the solution, known as sulphite cellulose lye, and washed with water. 

General characteristics of cellulose Structure of cellulose Chemical properties of cellulose Welting and swelling Degradation of cellulose Effect of other factors on cellulose Substances accompanying cellulose Hemicellulascs Lignin... 

During chlorination, destruction of the colouring matter and further decomposition of other substances accompanying the cellulose proceeds, all these substances being oxidized by chlorine or hypochlorite. 

Cellulose and other structural polysaccharides of cell walls are associated with different polymeric non-sugar materials that fix and firm the cell walls and also form their outer hydrophobic layers, which are impermeable to water. In nutrition, they are classified as dietary fibre. According to their chemical composition, substances accompanying polysaccharides are classified as lignin, phenolic compounds (tannins), proteins or lipids. 

Recently, the effect on the nitration product of beating the cellulose prior to nitration has been studied by Ellefsen [97] who confirmed the well-known view that beating of cellulose was accompanied by partial degradation to soluble substances. However, the molecular weight was unchanged in those fractions of cellulose that did not dissolve in water. 

Sprucewood holocellulose was treated with an endo-p-1,4-mannanase isolated from Aspergillus niger and an endo-/3-1,4-xylanase, two avicelases, and a cellobiohydrolase C isolated from Trichoderma viride. The mannanase hydrolyzed about a quarter of the mannan in 2-3 days without xylan or cellulose degradation. The xylanase hydrolyzed about half the xylan with 10% mannan solubilization. The three cellulases hydrolyzed up to 45% of the cellulose and 20% of the xylan, accompanied by 40-70% solubilization of the mannan. Combined xylanase-mannanase treatment hydrolyzed about half the xylan and mannan. Addition of mannanase to to cellulose-treated samples increased the degradation of the cellulose and mannan. Micromorphological studies of the variously treated specimens revealed a loss of substances in P/Slf T, and adjacent zones of S2 of the tracheid wall. 

The current observations confirm previous studies on beechwood and sprucewood holocellulose (7,10,19). The attack of the hemicellulose proceeds from the primary wall/Si as well as from the tertiary wall into S2 the pit chambers constitute preferred paths of enzyme diffusion into the walls. Also, substances of the middle lamella, especially in the cell corners, are removed by the xylanase and the mannanase treatments. Parallel to the removal of hemicelluloses, the fibrillar structure of the cellulose and its lamellar arrangement in transections of cell walls became obvious. In samples treated with cellulases, the cellulose fibrils were often completely hydrolyzed in the Si layer, occasionally accompanied by complete dissolution of cell-wall portions. This is also in conformity with the previous conclusion that the cellulases hydrolyze highly ordered zones of cellulose and remove hemicelluloses by hydrolysis or by detachment. 

Adsorption of water is accompanied with swelling of wood. Since cellulose constitutes almost 50% of the wood substance, its fractional contribution to sorption is the highest. Swelling of wood is thus manifested by the adsorption of water by hydroxyl groups located on surface of micells and amorphous regions of cellulose, crystalline zones being impenetrable. Reduction in... 

This substance forms a viscous solution in which the long-chain structure of the cellulose molecules is retained. Dilute mineral acids decompose it with the regeneration of cellulose, accompanied by the formation of carbon disulphide and sodium sulphate. 

Nearly all successful flame-resistant finishes depend upon the application of compounds contuining phosphorus to the cellulose. Not much is known about the combustion of cellulose, but it has been established that it breaks down into a solid carbonaceous char accompanied by the formation of volatile liquids, gases, and tarry substances. Anything which reduces the formation of volatile products of combustion will retard the rate of propagation... 

Until quite recently all methods of dyeing cellulosic fibres so that they would have really good wet-fastness depended upon converting soluble substances into relatively insoluble compounds in the fibre, and the processes were always accompanied by a measure of difficulty in application. Direct dyes lack wet-fastness because the forces which retain them on the fibre are easily broken. For a long time chemists have been seeking a method of joining the dye molecule to the cellulose with a covalent bond. 

In Experiment 13A, caffeine is isolated from tea leaves. The chief problem with the isolation is that caffeine does not exist alone in tea leaves but is accompanied by other natural substances from which it must be separated. The main component of fea leaves is cellulose, which is the principal structural material of all planf cells. Cellulose is a polymer of glucose. Because cellulose is virtually insoluble in water, it presents no problems in the isolation procedure. Caffeine, on fhe ofher hand, is wafer soluble and is one of the main substances extracted into the solution called tea. Caffeine constitutes as much as 5% by weight of the leaf maferial in fea plants. 

A great number of the measurements on permeability have been made upon the complex membranes of Table 112, in which the chemical nature of the membranes is briefly indicated. Most of the membranes sorb water freely. Natural rubber, one of the least hydrophilic of these substances, may if exposed to water vary from a non-swelling non-sorbing medium to complete dispersion in the water, according to the carbohydrate and protein content (3). Nearly all cellulose or protein-containing substances swell and sorb water strongly (4), and the accompanying sorption is then influenced by tempera-... 

Pancreozymin. As pointed out by the present authors in 1961 and 1962, it is quite remarkable how closely cholecystokinin and pancreozymin accompany each other during the various purification steps, whereas secretin separates very early. This applies to the chromatography on the acidic carboxymethyl cellulose and on the basic TEAE-cellulose up to a strength of 200-250 Ivy dog units of CCK per mg substance. 

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