The investigation described deals with the equilibria existing in a water solution of sulphur dioxide. The vapor pressures and conductivities of solutions of sulphur dioxide were measured over the temperature range 23° to 135 °C. at various concentrations up to 8%. The densities of the aqueous solutions up to 15% were also measured. A discussion of the various equilibria in the light of these data leads to the conclusion that sulphurous acid is one of considerable strength, its apparent weakness being due to the small amount of H2SO3 actually present. With rise in temperature the free sulphur dioxide increases and the hydrogen-ion concentration of the sulphite liquor used in current practice is so low that it seems highly improbable that the cooking reaction is due essentially to this factor. Apart from the bearing this work may have on the theory of sulphite cooking and the theory of the equilibria existing in the SO2−H2O system, it fills a considerable gap in the data regarding sulphur dioxide.

A method has been devised for the measurement of the dielectric constant of a material that cannot be made to completely fill a condenser. The following is the procedure adopted: Two completely miscible liquids are so chosen that the dielectric constant of the material under examination lies between the two values for the liquids. The dielectric constants of solutions of A and B ranging from 100% A to 100% B are measured. A curve is drawn showing the relation between dielectric constant and percentage composition. The condenser used is then partly filled with the fibrous material. The solutions of A and B are introduced into the condenser and the net dielectric constants are determined. A second curve is drawn showing this relation. The point of intersection of the two curves gives the composition of that liquid that has the same dielectric constant as the fibrous material.This method has been applied to the measurement of the dielectric constant of cellulose, benzene and ethylene dichloride being used. A value of 6.1 has been obtained for this constant.

Measurements were made of the amount of water vapor sorbed by beaten and unbeaten samples of kraft, unbleached sulphite and bleached sulphite wood pulps at relative vapor pressures ranging from 0 to 100%. Beating of the pulp made practically no difference to the degree of sorption at any relative vapor pressure. This indicated that beating caused no change in the hydration of the cellulose. Measurements were made of the sorption of methyl alcohol vapor by bleached sulphite, kraft and groundwood, and of the sorption of propyl alcohol vapor by bleached sulphite and cotton, all previously wetted with water and then dried. After sorption of alcohol, evacuation at room temperatures did not completely remove the alcohol. Measurements were also made of sorption of propyl alcohol by bleached sulphite and by cotton which had been dewatered by washing with propyl alcohol. The shape of the sorption curve was different for these samples, and the residual alcohol after evacuation was less. After a sample of cotton had been dried over phosphorus pentoxide in vacuo for a long period it was found to hold 0.35% of water by weight which could be removed by heating the cellulose to 100 °C. This was regained from the pentoxide on cooling the cellulose.The data are explained on the hypothesis that the crystalline submicroscopic elements of the cellulose structure are drawn together by internal tensile forces during the evaporation of the sorbed liquid, and that bonding between these elements may take place by the growing together of the crystal elements, leaving the structure internally stressed. On absorption, dissolution of these bondings takes place and the stresses are relieved as liquid enters the structure.

Three factors are involved in cellulose bonding--available area, contact, and hydrogen bonding.

The specific heat of cellulose has been determined for the temperature range − 70° to 25 °C. The heat capacity of water sorbed to the extent of 5.92 and 12.0% by cellulose has been determined for the range − 78.5° to 25 °C. These data are compared with the heat capacity of pure water for the same range of temperature, viz., − 78.5° to 25 °C.