Wettability of the Cellulose Walls of the Mesophyll in the Leaf

Abstract

THE moisture regain curves (sorption isotherms) of cellulose show a steep rise at high relative humidity, but the water content at saturation (about 18 per cent of the dry weight of raw cotton) is definite both for natural and for regenerated celluloses¹. To explain why no loosely adhering liquid condenses even when ample time is allowed for dispersal of the heat generated, it is sometimes suggested that the vapour, even under the best controlled experimental conditions, is never fully saturated. This view is, however, difficult to reconcile with the definiteness and reproducibility of the saturation maxima, especially as the regain curves are here so very steep. That these curves have a finite and not an infinite slope at saturation suggests another explanation, namely, that a clean cellulose surface may be incompletely wettable by water.