The Typical Cellulose and the Cellulose Group 23 



solutions of sodium hydrate at high temperatures upon the ligni- 

 fied tissue. It is assumed that the non-cellulose constituents of the 

 woods (see p. 172) are exclusively attacked by the treatment : 

 which, however, is by no means the case, as the results of Tauss 

 (loc. ctt.} sufficiently show. Quantitative results obtained by this 

 method have, therefore, only a limited value ; and, as estimations 

 of ' cellulose,' are subject to large and variable errors. 



CONCENTRATED SOLUTIONS OF THE ALKALIS. Cold solu- 

 tions of the alkaline hydrates of a certain concentration exert 

 a remarkable effect upon the celluloses. Solution of sodium 

 hydrate, at strengths exceeding 10 p.ct. Na. 2 O, when brought 

 into contact with the cotton fibre, at the ordinary temperature, 

 instantly changes its structural features, i.e. from a flattened 

 riband, with a large central canal, produces a thickened cylin- 

 der with the canal more or less obliterated. These effects in the 

 mass, e.g. in cotton cloth, are seen in a considerable shrinkage 

 of length and width, with corresponding thickening, the fabric 

 becoming translucent at the same time. The results are due 

 to a definite reaction between the cellulose and the alkaline 

 hydrates, in the molecular ratio C 12 H 20 O 10 : 2NaOH, accom- 

 panied by combination with water (hydration). The com- 

 pound of the cellulose and alkali which is formed is decom- 

 posed on washing with water, the alkali being recovered un- 

 changed, the cellulose reappearing in a modified form, viz. 

 as the hydrate Ci 2 H 20 O 10 .H 2 O. By treatment with alcohol, 

 on the other hand, one half of the alkali is removed 

 in solution, the reacting groups remaining associated in the 

 ra tio Ci 2 H 20 O, : NaOH. The reaction is known as that 

 of Mercerisation, after the name of Mercer, by whom it was 

 discovered and exhaustively investigated. Although, however, 

 it aroused a good deal of attention at the time of its dis- 

 covery, it remained for thirty years as an isolated observation, 

 i.e. practically undeveloped. Recently, however, the alkali 



