Experimental and Applied 305 



the middle ages these fibres were the staple raw materials for 

 production of papers, and in books that have come down to us 

 from these times there is sufficient evidence of resistance to 

 the natural processes of disintegration. 



Fibres of Class B have been introduced in response to the 

 enormously increased consumption of paper in this century, 

 and it becomes important to consider how far they fail, or may 

 on chemical evidence be predicted to fail, in regard to the 

 properties which distinguish the former class. It is evident 

 that chemically they are of totally different constitution, 

 esparto and straw diverging from the normal type much more 

 considerably than the wood-celluloses. It is a matter of ob- 

 servation that all papers containing these celluloses are liable 

 to discolouration under the ordinary conditions of wear and 

 tear. Chemists will have made the further observation that in 

 the atmosphere of the laboratory, reference books, or rather 

 the paper upon which they are printed, are liable to peculiar 

 discolourations. Thus, in laboratories where coal-tar products 

 are handled it is a frequent experience that our journals 

 change from white to bright pink, and even where there is 

 no direct contact with the atmosphere of the laboratory 

 it is common to see the pages change to various shades of 

 brown. This browning can be produced in a very short time 

 by exposure to the heat of the water-oven, and it has also 

 been shown that under these conditions the fibre undergoes 

 oxidation which is sufficiently marked to be measured by 

 an increase of yield of furfural on boiling with hydrochloric 

 acid. It is clear, therefore, that these reactive oxycelluloses 

 are inferior in an important chemical sense, and their use hi 

 books is open to the very obvious objection that the books are 

 more perishable. Of course, it is perfectly true that a large 

 amount of literature is of the ephemeral kind, and in this pro- 

 vince such questions as we have raised do not enter ; on the 



x 



