IDENTIFICATION OF FIBERS. 355 



The solution of iodin in zinc clilorid is prepared by taking 100 parts 

 of zinc clilorid solution of 1.8 sp. gr., adding 12 parts of water, and 6 

 parts of potassium iodid, then add iodin till the vapors thereof begin 

 to form. The brown liquid should be kept protected from light. 



The solution of cuprammonium is made by adding sodium carbonate 

 to a solution of copper sulphate, by which a mixture of copper hydrate 

 and carbonate is formed; this is well washed and treated with just 

 sufficient ammonia of 0.91 sp. gr. to dissolve it. It should be well 

 shaken, filtered, and is then ready for use. Anilin sulphate in 1 per 

 cent solution dyes woody fiber cells pale to deep yellow according to 

 the amount of woody deposit. 



The phloroglucin reagent requires two liquids which are kept sep- 

 arate, first a 5 per cent solution of phloroglucin in 95 per cent alcohol, 

 and second strong hydrochloric acid. Apply to the section under 

 examination first a drop or two of phloroglucin solution, and then in 

 like manner the hydrochloric acid. Lignified cells will be stained red, 

 those not lignified will remain colorless. This reagent is much used 

 f or determining the presence of wood pulp in paper claiming to be 

 made of rags. A 5 per cent solution of anilin clilorid may be substi- 

 tuted for the phloroglucin and applied in the same way, but the lignin 

 will be stained yellow instead of red. 



For the application of iodin and sulphuric acid, a little iodin is dis- 

 solved in alcohol, and diluted with water till a pale wine-colored liquid 

 is obtained. The sulphuric acid used should be diluted with two parts 

 of water, and the sample treated with the reagents alternately till the 

 full effect is produced. Fuchsin is employed in a 5 per cent alcoholic 

 solution. Lead acetate in 5 per cent water solution. Picric acid, a 

 saturated water solution. 



Vegetable fibers are composed of long cells, which may be attached 

 in a single row, end to end as in cotton, or, in bast fibers like linen and 

 hemp they are spindle-shaped with very tapering ends, which lie side 

 by side and are united to each other by a kind of cementing or inter- 

 cellular substance. Something of the strength of the fiber depends on 

 the strength and the resistance which this cement offers to the action 

 of ordinary solvents, like water and soap ; if it dissolves readily, as in 

 the case of jute, goods made of such a fiber will not stand washing. In 

 any case the fibers which are to be examined should be separated into 

 their ultimate cells by soaking in alkali, then rubbing between the 

 fingers or teasing out with needles, or recourse must sometimes be had 

 to boiling in a 10 per cent soda lye or labarraque solution, and fraying 

 in a mortar. 



When the ultimate cells are obtained, they should be stretched on a 

 slide moistened with a little glycerol for microscopical examination. 

 The glycerol will prevent any tendency to crisp or curl when they are 

 stretched out, and a cover glass laid on, and the whole slide is placed 

 upon a micrometer scale to measure the length. Transparent glass 

 scales may now be obtained, which are very convenient for this work. 



