204 Cellulose 



particularly the dye woods, logwood, brazil wood, sapan, &c., 

 &c. These characteristic products are well-defined, mostly 

 crystallisable compounds, the constitution of which is deter- 

 mined entirely without reference to the physiological problem 

 of their origin or their relationship, genetic or otherwise, to the 

 tissues in which they are stored up. 



The purpose of this treatise is, however, strictly limited to 

 the chemistry of fundamental tissue ; outside this lies the 

 indefinitely wide territory of plant secretions into which we 

 make no attempt to enter. 



We have now, in concluding our account of the lignocellu- 

 loses, to deal briefly with certain industrial processes which 

 throw further light on the chemistry of the lignocelluloses. 



(i) DESTRUCTIVE DISTILLATION. The products of the 

 destructive distillation of the woods are extremely numerous 

 and of varied constitution, comprising, in fact, representatives 

 of all the more important groups of C,H, and C,H,O com- 

 pounds. The formation of these products depends upon 

 various factors : (a) the composition of the wood itself, and 

 (^) the conditions of distillation. 



Ramsay and Chorley have made careful comparative 

 investigations of typical dicotyledonous woods oak, beech, 

 and alder and their results afford a general idea of the influ- 

 ence of these factors. The tables on the opposite page may 

 be cited in illustration (J. Soc. Chem. Ind. 1892). 



These results, as regards the solid residue (charcoal) and 

 gaseous products and their relation to the conditions of distil- 

 lation, are very complete and require no further discussion. 

 The increase of gas at the higher temperature of distillation is 

 formed at the expense of the charcoal, and CO at the expense 

 of CO 2 . 



In addition to these observations on the products, the 

 authors also found that the distillations were marked, as in the 



