3IO THE FORAGE AND FIBER CROPS IN AMERICA 



Cross section: shape; sketch. 



Identify kinds of fiber in woven cloth. 



400. VALUE OF FIBERS AS DETERMINED BY ACTION OF REAGENTS. For this 

 purpose, use samples of raw cotton, flax, and jute fibers. 



1. Resistance to bleaching: Boil a weighed portion, say two grams, in a 

 1 per cent, solution of caustic soda for five minutes. Determine loss in weight. 



2. Resistance to laundering: Boil a weighed portion in a 1 per cent, solu- 

 tion of caustic soda for one hour. Determine loss in weight. 



3. Percentage of cellulose: Boil a weighed portion in a 1 per cent, solu- 

 tion of caustic soda for five minutes, wash and expose to an atmosphere of 

 chlorine gas for one hour. Wash and raise slowly to boiling point in basic 

 sodium sulphite, and boil for three minutes. Wash and boil in 20 per cent, 

 solution of acetic acid. Washed and dried residue is weight of cellulose. 



4. To determine minimum loss in weight in clear raw fiber for commercial 

 use: Boil weighed portion of raw fiber in 20 per cent, solution of acetic acid 

 for one minute. Wash with alcohol and water, and determine weight of 

 dried residue. 



5. To note changes due to strong alkali and acid: Expose a small sample 

 to a 33 per cent, cold solution of caustic potash and another sample to equal 

 volumes of cold concentrated nitric and sulphuric acids for one hour. Note 

 results. 1 



401. COLLATERAL READING. E. A. Posselt: The Structure of Fibers, Yarns, 

 and Fabrics. 2 vols., pp. 13-15, 73-5, 189. Philadelphia: The Author, 215? 

 North Twenty-first Street, 1891. 



Julius Zipser (translated by Charles Salter) . Textile Raw Material? and 



their Conversion into Yarns, pp. 7-56. London; Scott. Greenwood & Co., 1901. 



C. R. Dodge: The Structural and Economic Classification of Fibers. In 



U. S. Dept. Agr., Fiber Investigations Report No. 9: A Descriptive Catalogue 

 of the World, pp. 9-33. 



J. Merritt Matthews: The Textile Fibres, pp. 97-1C9. New York: John 

 Wiley * Sons, 1904. 



1 For further details, see U. S. Dept. Agr., Fiber Investigations Rpt. No. 9 

 (1897), p. 19. 



