GENERAL MICROSCOPY 



The I'ullowiiig reaction times at 18°C can be 

 taken as normal for several thicknesses of wool : 



Dutch wool (37m) 12 min 



New Zealand (24^) 8 min 



Cape wool (20^) 8 min 



The first indication of blistering is at the ends 

 of the pieces. 



Cumulative damage may result in a normal re- 

 action time. 



Methylene Blue Test. 0.002-0.003% methylene 

 blue in distilled water. Pieces of wool about 5 

 mm long in methylene blue are microscopically 

 examined after the dye has acted for about 10 

 minutes. This reaction is used mainly to dis- 

 tinguish damage bj' heat from damage by alkali. 



Methyl Orange Test. The normal indicator 

 solution is used. In the case of wool this test is 

 used for: 



(a) detection of damage by light 



(b) retention of chemicals distinguishable by 

 color and formation of crj^stals of the acid 

 form of methyl orange, which is far less 

 water-soluble than the sodium salt itself. 



Congo Red Test. The Congo Red test is based on: 



(1) The varying diffusion at room temperature 

 of stains in the cuticula and in the secondary cellu- 

 lose layer of cotton fiber after this has been made 

 accessible to the stain to a greater or less extent 

 by swelling in caustic soda solution, with the re- 

 sult that the cellulose layer is stained a deeper 

 shade. 



(2) The behavior of cotton fiber when swollen 

 with caustic soda solution, especially as regards 

 the constricting effect of the cuticula. 



(3) Spiral splitting of the cuticula. The speci- 

 men of cotton for examination is : 



(a) soaked for 3 min in a sodium hydroxide 

 solution of a certain strength; this may con- 

 tain a wetting agent if desired. 



(b) washed with water. 



(c) placed for 10 min in a concentrated solution 

 of Congo Red. 



(d) rinsed. 



(e) placed in an 18% caustic soda solution. 

 This test is used for detecting various forms of 



damage to cotton. Although on the whole it al- 

 lows of explicit conclusions, it should be stated 

 that the result is entirely qualitative. 



Cotton Blne-Lactophenol. The fibers are heated 

 for 1 min in lactophenol, then stained for 5-10 

 min with a warm aqueous solution of cotton blue. 

 After rinsing with warm lactophenol they are 

 microscopically examined. This test is used mainly 

 for damage by molds. 



Mounting Methods. It is of major importance 



for the fibers to be mounted in a medium whose 

 refractive index does not vary too much from that 

 of the fibers. The following media are very satis- 

 factory: 



(1) Glycerin-gelatin: 7 g gelatin is soaked for 2 

 hr in 42 cc distilled water; 50 g glycerin and 0.5 g 

 phenol crystals are added; it is heated on a water 

 bath for 10-15 min, while stirring, and is filtered 

 through a glass filter, (n = 1.474.) 



(2) Canada balsam. 



(3) Broadfoot and Schwarz. Constituent parts: 

 isobutyl methacrylate (Du Pont), Aroclor 1242 

 (Monsanto), Xylene. 



IBM 



(cc) 



10 



18 

 18 

 18 



18 



Refractive index 



1.495-1.506 

 1.500-1.505 

 1.505-1.510 

 1.5ia-1.520 

 1.520-1.525 



(4) Aquamount (Gurr) 



(5) Glycerin 85% 



Special Micro-techniques. The fol- 

 lowing techniques are important in fiber re- 

 search : 



Micro-elongation tests. The fibers are fixed 

 tight at one end, and run over a pulley at 

 the other, on which a weight may be sus- 

 pended. To ensure that the same piece is 

 examined throughout the test, the method 

 may be varied by having a pulley and a 

 weight at each end. 



Micro-torsion tests. Here again the fibers 

 are fixed tight at one end. The other end is 

 fixed in rotating metal jaws. Great care must 

 be taken to ensure that the bearing and cen- 

 tering of the rotating part are very accurate 

 to avoid the fiber disappearing from view 

 during the test. 



Capillary rotator. For exact birefringence 

 measurement of fibers the fiber is placed in 

 a glass capillary. The capillary is filled with 

 a hquid whose refractive index is the same 

 as that of glass, and it can be rotated in the 

 same liquid. It is possible with a simple disc 

 to rotate the capillary with the fiber through 

 an angle of 90°. The double refraction of the 



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