Silk bleaching with

Nonabsorbable Natural Sutures. Cotton and silk are the only nonabsorbable sutures made from natural fibers that are stiH available ia the United States. Cotton suture is made from fibers harvested from various species of plants belonging to the genus Gossipium. The fiber is composed principally of ceUulose. The seeds are separated from the cotton boUs, which are carded, combed, and spun iato yams that are then braided or twisted to form sutures ia a range of sizes (Table 4). The suture is bleached with hydrogen peroxide and subsequendy coated (finished or glaced) with starch and wax. The suture may be white or dyed blue with D C Blue No. 9. 

Wool and Silk. Wool must be caretiiUy bleached to avoid fiber damage. It is usually bleached with 1—5% hydrogen peroxide solutions at pH 8—9 for several hours at 40—55°C or at pH 5.5—8 for 20—60 min at 70—80°C. Silk is bleached similarly, but at slightly higher temperatures. 

The adverse effects of alkali on wool cause reduction in its dry strength only after fiber solubilization and considerable loss in its cystine content (105). Because of its sensitivity to alkali, wool is preferentially given a peroxide bleach with added formic acid silk does not degrade nearly so much under alkaline conditions and may be bleached at pH 10 with peroxide, using stabilizers such as sodium silicate (98). 

Boil a second piece of dyed silk in a solution of chlorine water. (7) What effect was produced on the color (8) Was the strength of the fiber of the cloth effected Rinse the cloth under the tap and boil it in the solution of potassium chlorate. (9) Was the color restored (10) To what class of reactions does the bleaching process belong (11) What advantage does it possess over bleaching with sulphur dioxide ... 

The ancient process of stoving is stiU occasionally used to bleach wool and silk with sulfur dioxide. In this process, wet fabrics are hung in chambers of burning sulfur or sulfur dioxide gas for at least 8 h. The fabrics are then washed with sodium sulfite to remove excess sulfur dioxide. Fabric so treated may have unpleasant odors, and the original color eventually returns, but the process is simple and inexpensive. 

The chloroisocyanurates can be used in the bleaching of cotton, synthetics, and their blends they do, however, attack proteinaceous fibers, such as silk or wool, presumably via active chlorine reaction with the peptide (amide) linkage. However, the chloroisocyanurates can be used as shrink-proofing agents in wool finishing (131), (see Textiles Wool). The same action of chlorine upon proteins contributes to the effectiveness of chloroisocyanurates in automatic dishwashers. 

Calcium bisulphite is largely used in the manufacture of sulphite pulp, from which paper and viscose silk (see p. 264) may be produced. Wood chips or shavings are boiled with the bisulphite under pressure and so yield cellulose, which at the same time is bleached. The bisulphites of magnesium and the alkali metals are also sometimes used. 

The bleaching of silk, straw, wool, and other fabrics (This use depends on the fact that sulfur dioxide forms unstable colorless compounds with the colored pigments in these fibers because of the relative instability of these colorless compounds, the bleaching action of sulfur dioxide is seldom permanent.)... 

Recipe for Bleaching Silk with Hydrogen Peroxide... 

Reduction bleaching of silk is generally carried out with sodium hydrosulphite or appropriate stabilised commercial products on this basis. The silk fibrion is... 

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