BEFORE PAPYRUS . . . BEYOND RAYON — ESSELEN 177 



in dish- washing. Paper is the form of cellulose used for this treat- 

 ment. When special forms of paper are employed, the product 

 makes an excellent electric insulation. Treatment with concen- 

 trated solutions of zinc chloride produces a somewhat analogous 

 effect, the product being known as vulcanized fiber which finds many 

 uses in industry as for example in roving " cans " so-called, and 

 trucks for textile mills. 



For centuries cellulose in the form of linen and cotton has pro- 

 vided wearing apparel. Almost our earliest literature speaks of 

 purple and fine linen. Yet silk was always the fabric of the no- 

 bility and had a beauty and a feel which the cellulose fibers could 

 not match. Since the sheep converted the cellulose of hay and 

 grass into wool and the silk worm changed the cellulose of the mul- 

 berry leaf into silk, man has long been trying to find the secrets, par- 

 ticularly that of the silk worm. The natural raw material with 

 which to experiment was cellulose, at first that of the mulberry leaf 

 and later a purified cellulose. While the silk worm's secret has not 

 yet been found, ways have been developed, after years of research, 

 for producing from cellulose fibers which are as attractive as silk 

 to both eye and skin. In the four forms of rayon we have the first 

 man-made fibers and fibers which, therefore, are not subject to the 

 whims of nature for their production. 



The goal for which the early investigators in this field were striv- 

 ing, was the production of natural silk by artificial means. In fact 

 it has been said that its earliest designation, artificial silk, was given 

 to the new product in order to distinguish the silk made by artificial 

 means from that made by nature. It is well known now, however, 

 that none of the four varieties of rayon are in any way related 

 chemically to silk. The first three to be developed are all regen- 

 erated cellulose and quite similar in their properties, although the 

 series of changes through which they have passed from cellulose to 

 finished product are in each case quite different. The latest member 

 of the group is cellulose acetate, a chemical compound of cellulose 

 and acetic acid and quite different in its properties from either cellu- 

 lose or the other forms of rayon. 



In general the processes for the manufacture of synthetic fibers 

 may be divided into two classes, depending upon whether the finished 

 fiber is essentially cellulose, regenerated in a somewhat modified 

 form, or whether it is a compound of cellulose such as cellulose ace- 

 tate. All of the processes have certain underlying principles in com- 

 mon, involving first the conversion of the cellulose into a soluble 

 derivative, the solution of which is then forced through very fine ori- 

 fices into a hardening medium which may be either a liquid or a gas, 

 depending upon the character of the solvent. In the earliest process, 



