140 Cellulose 



action of bodies which selectively attack particular groups, its 

 highly complex constitution is brought into evidence. 



The reactions with the halogens just described, although 

 reactions of combination, also partake of the character of 

 decompositions, as the evidence has shown. We have now to 

 deal with the decompositions of the lignocellulose in their 

 order, and to emphasise the evidence which they afford as to 

 the relationships of the constituent groups of its complex 

 molecule. 



(i) Non-oxidising acids. (a) Hydrochloric acid. The fibre- 

 substance boiled with the acid of moderate concentration 

 (i - o6 sp.gr.) is profoundly attacked. Furfural distils, and may 

 be quantitatively estimated as already described (p. 99). 



The residue is a brownish-black mass of high carbon 

 percentage, presenting some features of resemblance with the 

 original, chiefly in its reactions with chlorine and nitric acid. 

 It is an ill-defined complex, however, and has been only super- 

 ficially investigated. 



(b) Hydriodic acid acts similarly in the earlier stages ot 

 its action. The reaction with this hydracid is made use of in 

 the quantitative estimation of the O.CH 3 groups of the ligno- 

 cellulose. The following determinations have been made in 

 normal specimens : 



(0 (2) 



OCH, . 4*5 4 -6 p. ct. of lignocellulose 



The acid acts, of course, as a deoxidising acid, and the 

 residue of the reaction is deserving of investigation with the 

 view to determine the limit of deoxidation. 



(c] Sulphuric acid. The dilute acid at the boiling tempera- 

 ture acts similarly to hydrochloric acid ; the volatile products 

 of the decomposition are furfural and acetic acid. In the con- 

 centrated acid the lignocellulose dissolves, forming a purple 

 brown solution. On pouring the solution into water a 



