IDENTIFICATION OF FIBERS. 353 



of chlorin, or with dilute acids, such as hydrochloric or sulphuric, of 



suitable strength. By the action of these reagents the vegetable mat- 

 ter is rendered brittle so as to easily break in pieces like dust when the 

 mixed mass is subjected to the action of a shaking machine known as 

 a willow, and this dust is blown away, leaving the wool substantially 

 intact. Mungo and shoddy are thus obtained. When hydrochloric 

 acid has been used as the disintegrating agent, if after its action the 

 fiber is steamed, the silk, if any is present, will also be partially dis- 

 solved so that it can be removed and a pure wool fiber obtained. 



In strong, cold sulphuric acid silk quickly turns yellow and dissolves : 

 cotton disintegrates slowly without color ; flax and hemp make a black 

 mixture, and wool is scarcely affected. Both silk and wool turn yellow 

 and are soluble in nitric acid, the first more speedily, while vegetable 

 libers are slightly affected. Vegetable fibers are composed almost wholly 

 of cellulose, which dissolves readily in Schweitzer's reagent, which is a 

 solution of copper oxid in ammonia. Vegetable fibers are also capable 

 of being nitrated in different degrees by the action of a mixture of sul- 

 phuric and nitric acids, forming soluble cotton, gun cotton, etc., impor- 

 tant products in the manufacture of photographic collodion, celluloid, 

 and explosives. 1 



Fibers may be presented for examination in the form of raw material 

 or as manufactured goods. In the first case it often happens that some 

 preliminary treatment is required to remove the in crusting or coating 

 material which would otherwise prevent the direct action of chemical 

 reagents upon the fiber. Animal fibers are covered with oil : cotton with 

 a vegetable fat, and bast fibers, like flax and hemp, have more or less 

 resinous cementing matter attached to them. This will usually be 

 removed by a preliminary soaking in ether or benzine, and, if desirable. 

 the weight of such adventitious matter can be determined by the dif- 

 ference in the weight of the material before and after treatment. In 

 the case of cotton a preliminary weak alkaline bath is often used. 



If the material is in a manufactured state, as spun or woven, the 

 warp and weft should be carefully separated, as they often consist of 

 different fibers, and the threads should be untwisted so as to give the 

 reagents free access to the entire surface of the fibers. They may then 

 be examined according to the tables on page 351. adapted from Dam- 

 mer's "Illustriertes Lexicon der Verfalschuuaen." 



•For further information on these subjects, consult Allen's Commercial Analysis 

 Vol. II. 



1221 7— No. 9 23 



