Page:Paper and Its Uses.djvu/120

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on the fibres more easily seen, and if a suitable stain is employed, some differentiation in colouring the various fibres takes place.

A good standard solution is iodine in potassium iodide, with an accessory acid solution:—

Iodine Solution. Accessory Solution
Iodine 1.15 gm. Glycerine 10 c.c.
Potassium iodide 2.0   " Water 05   "
Water 20 c.c. Sulphuric 15   "

A drop of the iodine solution is placed on the fibre on the slide. After a minute or so it is blotted off, and a drop of the accessory solution is added. The fibres are separated with teasing needles (needles mounted in wooden handles) until well distributed on the slide. A cover glass is cleaned by rubbing with a piece of wash leather, and dropped on the slide. The excess of solution is carefully absorbed with the filter paper, and the slide is ready for examination. A description of each of the principal fibres is given, with the normal dimensions of the unbeaten fibres and the coloration given by the solutions specified. For general examination the lower powers of the microscope will be found most useful, the higher magnifications being employed for studying the markings and other characteristics of the fibres. The dimensions given of cotton, linen, and hemp fibres will not be met with in papers made from those materials, as in beating the lengths are shortened, and frequently the fibres are split longitudinally. Tissues, copyings, and Bible papers show the greatest reduction of the fibres.

Cotton.— Fibre 30 to 40 mm. x .02 mm. Stained violet-red to brown. The fibres are long flattened tubes with large channel and numerous twists, blunt ends, and some fibres have cross markings. For a blotting the fibres are cut into short lengths, and the