IIBEKS (TEXTILE) 



occurs. With zinc chloroiodide a blue or violet 

 color occurs. With ammoniacal fuchsine a 

 pale red color occurs. In Cuoxam the fiber 

 does not dissolve as quickly as flax, while the 

 primary wall remains. 



Jute (Fig. 3a). Jute consists of fiber bun- 

 dles overlapping at the ends, thus creating a 

 continuous filament. The fibers are held to- 

 gether with gum, wax and lignin. The surface 

 of the fiber is smooth with few internodes. 

 The lumen is bigger than in flax. The cross 

 section is polygonal. 



In Cuoxam the fiber does not dissolve, but 

 swells. In zinc chloroiodide a pronounced yel- 

 low coloration occurs. With phloroglucino- 

 hydrochloric acid the fiber turns red. 



Ramie (Fig. 3b). A flat, ribbon-like fiber. 

 The elementary fiber is 8-10 cm long. The 

 surface is characterized by small cross stria- 

 tion and folds. The cell wall is thin, the 

 lumen flat. In Cuoxam the fiber dissolves 

 completely. With zinc chloroiodide it turns 

 blue-violet. 



Sisal. Stiff fibers, roughly cylindrical in 

 shape, with a characteristic widening in the 

 middle. Ends blunt and thick. Cross section 

 polygonal. Lumen usually fairly big. The 

 fibers often contain air bubbles. lodo-sulfuric 

 acid gives a yellow color. Defatted fibers 

 afterwards bleached in sodium hypochlorite 

 and rinsed in 90%-alcohol give a red color 

 in NHs vapor. 



Manila (Fig. 3b). Cylindrical fibers with 

 pointed ends. Cross section irregular to poly- 

 gonal. Lumen round. Cell walls thin. In the 

 fiber bundles there are often stigmata, i.e., 

 thick, silicon-containing plates. They can be 

 easily detected by macerating fibers in chro- 

 mic acid. With iodo-sulfuric acid a golden 

 yellow to green color occurs. 



Kapok (Fig. 3a). Air-filled, thin-walled, 

 long, smooth cells. The lumen is large. The 

 cross section is round to elliptical. With zinc 

 chloroiodide a yellow color occurs; with 

 phloroglucino-IICl pink. 



Regenerated Natural Fibers. Besides 

 protein fibers this category contains the cel- 

 lulose fibers. 



The protein fibers are made from casein, 

 zein, groundnut or soyabean protein. All 

 these fibers show very slight double refrac- 

 tivity and have irregular structures. Un- 

 dissolved or prcmatiu'ely coagulated protein 

 particles can be distinguished in the fibers. 

 Usually they have an irregular skin: air 

 pockets, spherulitic structures and crystals 

 are often found. 



More important tlian the protein fibers 

 are the cellulose fibers. 



Most kinds of regenerated cellulose have a 

 skin, which is formed directly in the coagu- 

 lation bath, and a medulla. In cross section 

 the fibers are irregularly sinuate. They show 

 clear longitudinal striation. 



The structure, skin, medulla, are particu- 

 larly easy to see with the polarizing micro- 

 scope as the skin has a higher specific double 

 refractivity than the pith. Irregular double 

 refractivity is also to be seen in the cross 

 section. 



The refractive index differences occurring 

 in the cross sections are readily demonstrable 

 with an interference microscope. The skin is 

 then particularly easy to see. Phase contrast 

 microscopic examination of cross and longi- 

 tudinal sections is also useful for structural 

 examination. With the electron micro.scope 

 it was possible, in addition to the skin, to 

 detect a very thin membrane, the cuticula 

 (Kassenbeck). In the medulla, fibrillar struc- 

 tures are found. The elementary fibrils are 

 70-90 A in diameter. These elementary fibrils 

 form packs of various sizes. 



Electron microscopic examination shows 

 the skin usually to have a spongy structure. 



With thallium and iodine reactions Hess 

 showed that viscose fibers had crosswise stri- 

 ation in the fibrils. In addition to a "small" 

 period of approx. 150 A, this .striation showed 

 a large period of 550-670 A. 



In many cases, both light and electron 

 microscopic examination shows the skin to 

 consist of several layers. 



Casein and Milk Wool. The fiber section 

 is round with several scallops. There is slight 

 longitudinal striation. 



357 



