Dr Fento7i and Mr Berry, Studies on Cellulose Acetate 17 



Our experiments have demonstrated that the destructive effect 

 of acids upon fabrics is dependent on the strength of the acid in 

 the physico-chemical sense. Hitherto it had been supposed that 

 esters were objectionable as dope constituents on account of the 

 possibilities of free acids resulting from hydrolysis. This, however, 

 we found not to be the case. As far as weak acids only are concerned, 

 tensile strength determinations gave excellent results; and fabrics 

 doped with acetic acid as the principal solvent compared most 

 favourably with others. 



In our experiments a large number of liquids have been 

 examined, not only from the purely practical point of view, but 

 also from a desire to obtain if possible some information with 

 regard to possible relationships between the nature of the liquid 

 and its solvent action. It is of course impossible to define strictly 

 the solubility of cellulose acetate in any given solvent owing to the 

 colloidal nature of the products. The term "positive" is used in 

 the following lists to imply that the liquid named has the property 

 of gelatinizing cellulose acetate and subsequently converting it 

 into a clear homogeneous "sol" without the aid of heat. All the 

 results were obtained with a sample of the material which yields 

 54 per cent, of acetic acid on cold alkaline saponification. 



Positive. 



Liquid ammonia, liquid sulphur dioxide, liquid hydrogen 

 cyanide, acetaldehyde, benzaldehyde, salicylaldehyde, acetone, 

 methyl ethyl ketone, suberone, acetonitrile, propionitrile, formic 

 acid, acetic acid, butyric acid, formamide, ethyl formate, ethyl 

 oxalate, ethyl malonate, etbyl acetoacetate, aniline, phenyl- 

 hydrazine, ortho-toluidine, piperidine, pyridine, tetrachloroethane, 

 nitrobenzene*, nitromethane, cyclohexanone, guaiacol, chloro- 

 form*. 



Although cellulose acetate is insoluble in water and in absolute 

 ethyl alcohol, a mixture of these two liquids dissolves it freely 

 on boiling. On cooling, however, precipitation takes place almost 

 completely. 



Negative. 



Liquid air, liquid ethylene, liquid nitrous oxide, liquid hydrogen 

 sulphide, benzene, toluene, turpentine, carbon disulphide, carbon 

 tetrachloride, alcohol, ether, ethyl chloride, acetal, dimethyl 

 acetal, nickel carbonyl, and many other liquids. 



No general conclusion can be drawn as regards the chemical 

 nature of a liquid and its solvent action on cellulose acetate. It is, 



* Nitrobenzene requires certain additions. Chloroform had only a partial 

 solvent action on this specimen of the material. 



VOL. XX. PART I. 2 



