The Bonding Force of Cellulosic Materials for Water (from Specific Volume and Thermal Data)

An attempt was made in a previously reported research (14) to determine the volumetric contraction occurring in the water adsorbed by cellulosic materials. Apparent density measurements of wood and cellulose containing various amounts of adsorbed water were made in benzene. Benzene causes no swelling of cellulosic materials, indicating that its affinity for cellulosic materials is small. This, together with the fact that the internal surface of contact is relatively small, would make the adsorption compression of benzene negligible. It is questionable, however, that benzene penetrates the void structure of the dry cell walls completely. For this reason the benzene can be relied upon as a displacing medium only when the moisture content of the cellulosic material is sufficiently high for water to have opened up or itself filled all of the void structure. It was shown that the volumetric contraction occurring in the adsorbed water could be calculated down to a moisture content of about 6 per cent from the measurements in benzene. Below this point accurate data for the true density of the cellulosic material are required to make the calculations. Howard and Hulett (6) have determined the density of carbon in helium and have shown that at room temperatures the helium is practically nonadsorbed. Davidson (3) similarly concluded that helium is non-adsorbed on cellulose. Because of its low molecular weight it should further penetrate the void structure completely. Hence measurements of the density of the same cellulosic materials used in the previous investigation were made in helium. The essential features of the apparatus used for making the density measurements are shown in figure 1. A and B are two Pyrex glass bulbs of about 200-cc. capacity, separated by a stopcock S1. The sample bulb