The swelling of charcoal. Part I.—Preliminary experiments with water vapour, carbon dioxide, ammonia, and sulphur dioxide

Abstract

The experiments of Meehan having shown that charcoal increases in volume when taking up carbon dioxide, it became an obvious step to correlate this expansion with the quantity of gas adsorbed. In this paper a form of extensometer is described which, while sufficiently sensitive and accurate for the measurement of the percentage linear expansion ( x ) of a rod of wood charcoal, was yet compact enough to permit its being sealed up in an all-glass apparatus, so that simultaneous determinations could be made of the weight ( s ) of gas taken up per unit weight of the absorbent. The graphs obtained by plotting the variables x and s have certain interesting characteristics which it will be convenient to describe before dealing with the detailed results. As fig. 1 shows, the coefficient dx/ds increases steadily with s ; thus far the charcoal behaves similarly to many of the common gels, which contract proportionately less in the later stages of drying, owing to the micellæ coming in contact with each other. The swelling of charcoal, however, appears to follow a more regular course than that of the elastic gels, and in the case of ammonia, carbon dioxide, and sulphur dioxide is given within the limits of accuracy of our experiments by hyperbolic equations of the type x = k s /S— s ... where k and S are constants characteristic of each gas. In fig. 1 the experimental values of x have been plotted (for convenience of representation) against s /S. The smooth curves for ammonia of the above form, using appropriate values of the constants. An additional term (a small additive constant over the experimental range) is necessary to represent the behaviour of water vapour.

Influence of Elastic Strains on the Adsorption Process in Porous Materials: An Experimental Approach

“…[3,10,11] This relation is the result of two equilibrium conditions, one thermodynamic and the other mechanic. [9] This means that a stress external to the porous layer can change the adsorbed amount and hence the condensation pressure.…”

“…We have no information on the elastic deformation (δa/a) of the supported porous layer and the corresponding membrane during N 2 adsorption experiment, but several investigators [3,10,11] have shown that, in the region preceding capillary condensation, the linear deformation of porous materials is related to the adsorbed amount by the equation…”

“…This allows us to introduce in the thermodynamic relationships, in addition to the classical surface free energy, the elastic energy stored in the solid, which is, for small deformations, quadratic in the deviation. The mechanical equilibrium obtained by the minimization of the free energy of the adsorbate-solid system with respect to the deformation results in the linear variation of the deformation with the surface free energy observed by some investigators, [3,10,11] with the proportionality factor depending on the elastic constants of the solid.…”

Origin of Drying Shrinkage of Hardened Cement Paste: Hydration Pressure

“…Meeham 1927; Bangham and Fakhoury 1930;Hains and McIntosh 1947;Amberg and McIntosh 1952;Hiller 1964;Bentz et al 1998 ). However, significant differences in sorption isotherm and length-change isotherm between hardened cement paste (hereafter referred to as hcp) and other porous materials are known to exist, as shown in Fig.…”

Adsorption-induced deformation of nanoporous materials—A review

“…Based on a series of experiments, [71][72][73][74] which all showed monotonic expansion of charcoal samples with increased adsorbate pressure, Bangham concluded that the measured linear strain is proportional to the decrease in the surface energy c of a solid, caused by adsorption…”