Experimental and Applied 273 



advantage of chemical reactions to differentiate the fibres, the 

 method then consisting in the approximate estimation by actually 

 counting the fibres visible in the microscopic field according to 

 their identity, and averaging the results over a sufficient number of 

 separate examinations, and, where possible, by separate observers. 

 This, again, is a species of investigation which requires considerable 

 experience, which cannot be communicated in the form of working 

 directions. 



(4) For actual quantitative work, of course, any of the reactions 

 of which full details have been given in the earlier sections of 

 the work are available. Thus, for instance, in white paper, found 

 as above to be composed of rag fibres and celluloses of the Gra- 

 mineae only (esparto and straw), it will be evident that, as the 

 latter yield 12-14 P-ct. of furfural on boiling with hydrochloric 

 acid, and the former at the outside 0-5 p.ct., a furfural estimation 

 in the usual way (p. 99) would give a close approximation to 

 the proportions of the two groups of cellulose. In the case of 

 mechanical wood pulp, if the proportion is high, there are two or 

 three reactions available as a quantitative estimation. First, the 

 statistics of chlorination according to the methods described on 

 p. 104. Secondly, estimation of furfural ; but this is only available 

 in the absence of celluloses of the Gramineas. Thirdly, methyl esti- 

 mations ; which, again, depends on the ascertained absence of other 

 fibres also containing this group. Fourthly, the colour reactions 

 with derivatives of ^-phenylene-diamine, as described on p. 174. 

 And, lastly, the elementary analysis might even be made and taken 

 as a basis for calculating the proportion. These brief notes will be 

 sufficient to show the student how to set to work in the laboratory 

 to examine these particular mixtures of fibres with the help of the 

 reactions previously described in detail. 



Principles of Cellulose Technology. 



Following these notes of laboratory and general experimental 

 methods, we shall briefly discuss the applications of theoretical 

 principles and deductions to the practical processes of the arts. 

 The celluloses and compound celluloses are familiar to us in 

 multitudinous forms, both * useful ' and * ornamental ' ; and the 

 processes by which they are manufactured, or treated for various 



