FOREST UTILIZATION 109 



hours, when the yeast has dropped down to the bottom of the 

 vat while the sugar has been converted into alcohol. 

 The liquid is distilled and redistilled, yielding alcohol of any de- 

 sired concentration. 



The wood remaining only 20% of its weight seems convertible into 

 sugar might be used for paper manufacture or as fuel for the 

 boilers. Classen claims, after his methods, to obtain at least 

 30 % dextrose from absolutely dry wood. 

 D. Output. 



One hundred pounds of dry wood are said to actually yield about 

 5 pounds of 96 % alcohol. The process of manufacture is far 

 from being perfect. A number of chemists, notably Classen, 

 are hard at work to further improve and to cheapen the process. 

 Cheap alcohol a fuel, a source of light and a source of tech- 

 nical energy manufactured from wood will be a boon for 

 household, industries and forest. 



XXXVII. ARTIFICIAL SILK MADE FROM CELLULOSE. 



A. History. * 



Artificial silk was first prepared by Hilaire de Chardonet in 1884. 

 Today many patents and numerous factories to exploit them 

 exist in the old country. 



B. Process. 



There are two main processes in use, namely : 



I. A solution of nitrocellulose, a compound of nitric acid 

 and cellulose in ether or alcohol, is pressed through 

 minute capillary pipes, appearing in long, silky threads. 

 Additional chemicals (methods of Vivier, Lehner) re- 

 duce or entirely destroy the inflammability of the 

 product. 



II. Pure cellulose is readily dissolved in a few chemicals 

 only.notably in concentrated copper oxide dissolved in 

 ammonia. This solution forms a waxy mass which is 

 pressed through minute capillary openings and appears 

 in the form of supple, long, silky threads, immediately 

 entering a bath of sulphuric acid. Here cellulose is set 

 free, now a solid thread, while blue vitriol and sul- 

 phate of ammonia result at the same time. The threads 

 are spun exactly like threads of natural silk. 



C. Qualities of product. 



Artificial silk has an exquisite shine and is easily colored before 

 the pressing process. The tearing strength of silk obtained from 

 nitrocellulose, however, is now only 33% of that of true silk, 

 its toughness only 45%. 



Artificial silk is used on a daily increasing scale in silk weavings. 

 New methods and modifications of manufacture continuously 

 increase its chances as a substitute for natural silk. 



