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Holocellulose chlorite

Holocellulose was isolated from bamboo powders by removing lignin and resinous compounds using alternate treatments of glacial acetic acid and sodium chlorite at 70-80 C for three hours according to the method of Ku and Chiou (20). [Pg.234]

Wise and RatlilF extracted slash pine Pinus caribaea) chlorite holocellulose at 20° with increasing concentrations of aqueous potassium hydroxide. In the range of 2 to 10% potassium hydroxide, the larger part of the hemicelluloses dissolved. Thereafter, less material dissolved, and above 16% potassium hydroxide, the weight of residue remained constant. The hemicelluloses could be recovered quantitatively by acidification of the alkaline extracts with acetic acid, followed by precipitation with an excess of ethanol. For the practical purposes of analysis, Wise and Ratliff chose to divide the... [Pg.318]

Wise has recently suggested that fundamental studies on holocellulose should now be undertaken. He proposes that holocellulose prepared by both the chlorite procedure and the chlorine-alcohol-ethanolamine technique should be methylated, and the products fractionated and methanolyzed according to the established techniques of carbohydrate chemistry. [Pg.320]

Another method of isolating holocellulose from wood and similar lignified tissues by the use of sodium chlorite and acetic acid was devised by Jayme and modified by Wise, Murphy and D Addieco. The latter... [Pg.188]

Holocellulose. Holocellulose is the total polysaccharide (cellulose and hemicelluloses) content of wood, and methods for its determination seek to remove all of the lignin from wood without disturbing the carbohydrates. The procedure generally used (34) was adopted as Tappi Standard T9m (now useful method 249), and as ASTM Standard D 1104. Extracted wood meal is treated alternately with chlorine gas and 2-aminoethanol until a white residue (holocellulose) remains. The acid chlorite method is also used (3). The... [Pg.69]

IR spectroscopic evidence for covalent urethane bond formation in the reaction between isocyanates and wood has been obtained. Isolation of holocellulose by the sodium chlorite method, isolation of lignin by the H2SO4 procedure, and subjecting both to IR spectroscopy indicated that isocyanates reacted with both cellulose and lignin (194),... [Pg.392]

By examination of the spectra in Figure 5, it is clear that polysaccharides (holocellulose, peaks at 72 and 106 ppm) are dominant in the delignified humin in the upper layers of peat but diminish in relative concentration with depth. This trend was also observed in the spectra of humin in Figure 2. At depth, the polysaccharides are minor compared to the paraffinic carbons (peak at 30 ppm). Thus, the paraffinic structures in humin are resistant to sodium chlorite oxidation, and their relative increase in concentration with... [Pg.292]

The third reagent used for the preparation of wood holocelluloses, per-oxyacetic add, is of more recent date. It has been claimed to have certain advantages over sodium chlorite. Leopold found that the peroxyacetic acid method, when used in conjunction with sodium borohydride, gives a superior holocellulose. It is interesting to note that both peroxyacetic acid and chlorine dioxide are, apparently, able to effect an oxidative ringopening of phenolic compounds. ... [Pg.260]

In an attempt to isolate a water-soluble 0-acetyl-(4-0-methylglucurono)-xylan from a birch chlorite holocellulose, Marchessault and coworkers kept the time of contact between the ammonia and the holocellulose at a minimum. Successive extractions of the pretreated holocellulose with water and methyl sulfoxide removed the xylan in yields of 7.1 and 14.6%, respectively, based on the weight of the original wood. The products still contained most of the iironic acid, but only one third of the 0-acetyl groups of the native xylan. [Pg.264]

A chlorite holocellulose from white-birch wood, on extraction with methyl sulfoxide, gave a xylan containing 5.3 0-acetyl groups per ten xylose residues. In this case, the yield was only 5% of the original wood. The hemi-cellulose contained 58.1% of unsubstituted, 11.8% of 2-0-substituted, 24.0% of 3-0-substituted, and 6.1% of 2,3-di-O-substituted xylose residues. The 0-acetyl groups in native hardwood xylans are thus distributed between C-2 and C-3 of the xylose residues, with the majority located at C-3. It should, perhaps, be pointed out that, so far, only this species has been investigated, and moreover, only a minor part (15%) of the xylan portion of this wood has been studied. [Pg.276]

Fagus sp. Chlorite holocellulose, alkali Chlorite holocellulose, alkali 8 157... [Pg.282]

As the chlorine-2-aminoethanol method offers no obvious advantages in the case of softwoods, most investigators have used chlorite holocelluloses for isolating the hemicelluloses. The most common procedure has been to subject the holocellulose to a preliminary extraction with aqueous potassium hydroxide or sodium hydroxide solution. Low concentrations of alkali favor removal of the acidic xylan, as does the use of potassium... [Pg.435]

In one study, an arabino-(4-0-methylglucurono)xylan of pine had to be isolated in the pure form without the use of any alkaline reagents. A chlorite holocellulose was extracted with methyl sulfoxide, followed by hot water. The product from the latter extraction was dissolved in water, and a xylan-rich fraction was precipitated by adding cetyltrimethyl-ammonium bromide. When a chlorite holocellulose of spruce was extracted with methyl sulfoxide and then with water, the former extract was richer in xylan, and the latter in glucomannan. ... [Pg.437]


See other pages where Holocellulose chlorite is mentioned: [Pg.26]    [Pg.88]    [Pg.160]    [Pg.302]    [Pg.321]    [Pg.324]    [Pg.462]    [Pg.463]    [Pg.124]    [Pg.223]    [Pg.18]    [Pg.309]    [Pg.310]    [Pg.318]    [Pg.332]    [Pg.71]    [Pg.202]    [Pg.204]    [Pg.292]    [Pg.292]    [Pg.292]    [Pg.268]    [Pg.268]    [Pg.276]    [Pg.259]    [Pg.260]    [Pg.261]    [Pg.262]    [Pg.262]    [Pg.263]    [Pg.264]    [Pg.264]    [Pg.275]    [Pg.282]   
See also in sourсe #XX -- [ Pg.332 ]




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