Experimental and Applied 269 



latter should be carried out with certain precautions (see p. 96), 

 and the chlorinated fibre may be washed, and the washings titrated, 

 to determine the HC1 formed. 



The fibre may then be subjected to any of the special treatments, 

 according to the group to which it is assigned. 



Fibrous raw materials of more complex constitution must be 

 examined with reference to external appearance, and the direc- 

 tions of application for which intended. If for the isolation of 

 a textile fibre, the material is subjected to a prolonged boiling 

 with sulphite of soda solution (?, p.ci. Na a SO 3 ). The progress of 

 the disintegration is watched, and when the adventitious tissues 

 are sufficiently softened, the disintegration is aided by mechanical 

 means crushing, rubbing, &c. and the cellular debris washed 

 away in a stream of water. When perfectly cleaned, the proportion 

 of fibre obtained is estimated. In the case of bast fibres, the entire 

 bast may be stripped from the wood at an early stage, and the 

 further purification proceeded with as described. 



Where the raw material is to be examined for paper-making 

 purposes although it is possible to calculate with a fair amount of 

 accuracy, from the quantitative data obtained on the small scale, 

 the probable value of the material to the papermaker it is ad- 

 visable to carry out an experiment on a larger scale, under conditions 

 similar to those which usually obtain in the papermaker's pulping 

 process. For this purpose special apparatus is necessary. Thus, 

 to make a complete examination, the material requires to be boiled 

 under pressure with a quantity of caustic soda calculated from the 

 data obtained on the small scale, and this must be carried out in a 

 digester capable of resisting steam pressure up to (say) about 100 Ib. 

 per square inch. After the digestion the pulp must be removed, 

 washed on a wire gauze filter, and then put through a quantitative 

 bleach operation. For this purpose the pulp should be well broken 

 up, placed in about 30 times its weight of water (estimated), and 

 bleaching powder solution is added, calculated to (say) 20 p.ct 

 on the weight of the pulp obtained, which will be approximately 

 known from the cellulose estimations by the laboratory methods. 

 When the material is bleached, an aliquot portion of the residual 

 liquor is drawn off, and in it the residual hypochlorite is estimated 

 by the usual methods. The difference gives the amount actually 

 consumed in bleaching the pulp. The pulp is then washed off and 



