Sur le Mécanisme d'Adsorption et de Désorption des Solutions aqueuses de Soude dans les Fibres de Cellulose–Equilibres de Fixation de la Soude (3éme Comunication)

This is the third paper of this series published in this journal. The two previous papers dealt with a theory of interaction between cellulose fibers and aqueous solutions of sodium hydroxide. This interaction depends on several factors: For a given temperature, accessibility phenomena limit the penetration of soda solutions into native fibers (not previously mercerised) according to concentrations and types of fibers. An equilibrium for the fixation of sodium hydroxide is established within the parts of the fibers where penetration has occured. The equilibrium conditions are strictly independent of the type of fiber used. Fibers previously mercerised are fully accessible whatever may be the concentration of sodium hydroxide solution used. In the first part of this paper it is shown that the equilibrium equation previously set up, quantitatively fits the observed data. Desorption phenomena are then studied: displacement of 20% sodium hydroxide solutions from mercerised fibers by more dilute solutions. New accessibility phenomena are pointed out. A sodium hydroxide solution (concentration C < 20%) can penetrate or displace a fraction y only of the fiber soaked with 20% sodium hydroxide solutions. Values of y vs. C are given A simple thermodynamic treatment explains the observed phenomena.