Appendix II 315 



cellulose are expressed in terms of these units. But in these 

 reactions the factor of mass, as distinct from relative molecular 

 mass, has to be taken into consideration ; and, to cite a particular 

 case, the recent elaborate investigations of W. Will on the nitra- 

 tion of cellulose, and the decompositions of the nitrates by heat, 

 lead to the conclusion that in both directions there are no breaks 

 of continuity corresponding with definite reacting units of relatively 

 small dimensions. (Infra, p. 317.) 



This problem of the relation of molecule to mass necessarily 

 also arises in regard to the structural peculiarities of cellulose. 

 The conversion of cellulose into films, threads, and generally into 

 solids of continuous dimensions, has shown that the mechanical 

 properties of these solids are a direct function of the molecular 

 state of the parent substances, whether celluloses or cellulose 

 derivatives. Thus the hydrocelluloses (p. 54) are formed from the 

 ribrous celluloses at the expense of their tenacity : similarly, when 

 converted through soluble derivatives into continuous solids, these 

 are brittle and of low tenacity. The normal acetates give tough 

 rilms ; but if the acetylation is carried to the point that chemical 

 disintegration begins, as evidenced by the presence in the product 

 of reactive CO groups, the product gives brittle films. 



These considerations may be borne in mind in regard to the 

 future investigation of the problem. But the problem is without 

 present promise of solution, and it must be admitted that we have 

 no criterion of the kind or degree of association of the molecular 

 units in the complex aggregates of the cellulose group. 



Esters. On the general subject of the nitric esters of the 

 carbohydrates Will and Lenze have made investigations leading 

 to the conclusions that whereas the aldoses are fully esterified, the 

 hexoses giving pentanitrates and the pentoses tetranitrates, the 

 ketoses with n.OH groups yield nitrates containing n 2. O.NO 2 

 groups as a maximum, the two remaining OH groups passing into 

 the anhydride form. These nitrates of the ketose-anhydrides are 

 distinguished by much greater stability. (Berl. Ber., 1898, 68.) 



The authors have investigated the reaction of formation of 

 these nitric esters under the usual conditions of treatment of the 

 celluloses with a mixture of nitric and sulphuric acid, and conclude 

 from their experiments that the latter acid reacts also with the 

 cellulose hydroxyls. The fixation of SO 4 H residues in some 

 quantity is proved by analysis of the products formed under 

 certain conditions ; and the fact has to be taken into account 



Y 2 



