Cellulose, alkali bases

Almost pure cellulose is found in pith, absorbent cotton in some filter papers. Pure cellulose is most readily obtd from cotton by treating it with dil alkalies acids and thoroughly washing, with water. Another source of cellulose is wood(mostly coniferous) which contains 50-60% cellulose and strawfmostly cereal) which contains 30-40%. A common classification of celluloses is based on their solubilities in aq alkalies If cellulose is treated with NaOH soln of ca 18% at 20°, it will swell and much of the material, which is of short chain length, will dissolve. The residue from this treatment is called alpha cellulose. 

Oil-base (including oil-modified alkyd resin) paint films should not be used in alkaline environments as the paint will deteriorate owing to saponification alkali-resistant coatings are provided by some cellulose ethers, e.g. ethyl cellulose, certain polyurethane, chlorinated rubber, epoxy, p.v.c./ p.v.a. copolymer, or acrylic-resin-based paints. In particular, aluminium and its alloys should be protected by alkali-resistant coatings owing to the detrimental effects of alkali on these metals. 

Base liner, in landfills, 25 877 Base manufacture, of soap, 22 736-741 Base metal catalysts, 10 47 Base metal oxide catalysts, 10 100 Base-metal thermocouples, 24 461 Base oils, 15 215 Base plate dental wax, 3 298 specification, 8 300t Bases. See also Alkalis Basic entries cellulose as, 11 266... 

Other water-soluble polymers which do not tend to suffer from problems of retrogradation are sometimes used when different properties are required. Soluble cellulose derivatives, particularly car-boxymethyl cellulose, which is prepared by reaction of high purity cellulose with chloroacetic acid in the presence of alkali (equation 8.1), is popular for surface sizing base papers which are subsequently to be coated, because it assists in water removal when the coating mix is applied. 

This is an Sn2 reaction, which is proportional to the concentration of the epoxide and alkali cellulose, but since the base is regenerated, it is first order in epoxide. 

Makolkin studied the rate of exchange of, 80 between labeled water and alkali cellulose, and between labeled water and the trisodium alcoholate of cellulose, and concluded that mercerization proceeds by reaction that is, alkali cellulose is an adduct. He based his condition on the fact that there is no measurable exchange between water and the alcoholate, whereas there is measurable exchange between alkali cellulose and water. His conclusion, which is based upon difference of rate, is, however, not necessarily valid. The trisodium alcoholate may not possess a structure that is as accessible to water as is that of alkali cellulose. 

Regeneration of cellulose-based columns is most reliably achieved by using the acid/alkali precycling procedure described (see Note 13). 

Vat dyes are water-insoluble, organic pigments that are used to dye cotton and other cellulose libers. The principle of vat dyeing is based on chemical reduction of these dyes to the leuco compounds, which are soluble in aqueous alkali and exhibit fiber affinity, followed by reoxidation within the fiber to the water-insoluble starting dye. 

Cellulose is designated a, 3, and y on the basis of alkali solubility. a-Cellulose is that fraction not removed by treatment with 17.5% NaOH at 20°C the 17.5% NaOH-soluble fraction contains (3- and y-cellulose. The subfraction precipitating after acidification of the alkaline liquid phase is P-cellulose y-cellulose is the acid- and base-soluble subfraction remaining dispersed. a-Cellulose contains the highest DP. 

In this book, he emphasized the importance of the microscopic and the submicroscopic structure of fibrous high polymers. The reactions of cellulose with water, aqueous alkalis, organic bases, ammonia, and strong salt solutions were all stressed. Special attention was given to various types of cellulose esters, to cellulose xanthate, and to the cellulose ethers. The oxidation of cellulose under a variety of conditions was described, as were the hydrolysis reactions. The latter included discussions on reversion and on the kinetics of acid hydrolysis. It is interesting to note that Heuser, who earlier had criticized the terms hydrocellulose and oxycellulose, and had... 

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