Abstract
As a step to explicate the spinning mechanism of viscose rayon, the dehydrating power of aqueous inorganic electrolyte solution containing sulphuric acid was studied.
The amount of hydration of electrolytes in solution was determined by the ultrasonic velocity using the interferometer previously described. For Na2SO4 solutions containing H2SO4 or HCl, an anomalous phenomenon was observed in sonic velocity -concentration relationship when molar concentration of Na2SO4 was lower than that of the acids. However such an anomaly was not observed for NaCl solutions containing these acids.
The dehydrating power was calculated assuming that the amount of hydration could be obtained by Wada's formula when molar concentration of Na2SO4 is higher than that of H2SO4. The results show that dehydration power of aqueous Na2SO4 solution is reduced by the presence of H2SO4, but those of NaCl or NaNO3 solutions are not altered by H2SO4.
The dehydration index defined for the electrolyte solutions by the above investigation was linearly correlated with the coagulation index for partially saponified polyvinyl alcohol and polyvinyl pyrrolidone solutions.
From this and previous study, we conclude that the following four factors should be considered in understanding the viscose coagulation in the bath containing H2SO4 and Na2SO4.
a) Suppression of H+ by Na2SO4.
b) Suppression of diffusion of H2SO4 into viscose by Na2SO4.
c) Osmotic dehydration.
d) Decrease of dehydrating power of Na2SO4 by H+
