•24 - Mr. Charles F. Cross [March 2, 



varnish for metallic surfaces, and notably for electrical insulation 

 and applications whicli depend upon exceptionally low inductive 

 capacity. 



In the above brief account of the cellulose nitrates and acetates 

 there is the implicit suggestion of the production of artificial textile 

 threads by drawing the solutions of these bodies through orifices of 

 suitable form and dimensions, such that after removal of the solvent 

 liquid tlie re-solidified and structureless ester constitutes a cylinder 

 of hyaline material of uniform diameter. 



The industrial production of artificial threads, and notably of the 

 " silk " or lustra cellulose, we owe to the pioneer enterprise and 

 purposeful tenacity of a French technologist, H. de Chardonnet. 

 But cellulose nitrate as matiere premiere has many and obvious 

 defects ; hence the alternative plastic forms or derivatives of cellulose 

 have progressively displaced the original industrial product, which had 

 a brilliant career of success in the early years of this century. 



There are three main rival processes of which the underlying 

 ])rinciples are common. They are expressed in the stages or phases 

 of the process : — 



(1) Cellulose is transformed by reaction into a synthetic deriva- 

 tive — dissolved as such to an 8 per cent, solution (calculated as 

 cellulose), filtered and continuously projected, or drawn through fine 

 tubes or orifices, into a solidifying or setting medium. 



(2) The thread us a unit filament (monofil, crin, crinole), or 

 multiple group of twisted filaments (artificial silk), is a cellulose ester 

 or other derivative, and is chemically treated to remove combined 

 groups, or impurities as by-products of decomposing reactions ; the 

 thread substance is cellulose, reappearing as such after the cycle of 

 changes. 



The three cellulose derivatives on which these important industrial 

 processes are based are : (1) The nitric esters ; drawn or " spun," as 

 ether-alcohol solution (Chardonnet process). 



(2) The ammonia-soluble cellulose-hydrate-copper-hydroxide com- 

 pounds (Cuprammonium process). 



(3) The xanthic or sulpho-carbonic ester, synthesized in two 

 stages : {a) mercerization of the cellulose ; {b) combination of the 

 alkali cellulose with carbon disulphide, and solution of the product in 

 water (Viscose process). 



Of these the Viscose process is now predominant by reason of its 

 advantages, technical and economic. It will be noted that the 

 material " elements " of the industry are cellulose, common salt, 

 carbon and Buli)hur, than which no simpler terms could be devised, 

 even as an a priori proposition. 



Of other industrial a])plications of the Viscose process, the pro- 

 duction of transparent film in continuous length is a variation only 

 of the process al)ove descriljed, the licpiid Viscose being drawn througii 

 a controlled adjustal)le slit of 1-5 m. width, into a setting solution 



