AbstractEquations are derived which relate the pore volume and the volume of pores accessible to sorbate with the constitutive volumevAA, the electrostriction of sorbate by the charged groups of woolvE, and the volume contraction of sorbate in the neighborhood of nonpolar side chainsvNP. The pore volume and the volume of pores accessible to sorbate are calculated by use of values ofvAA andvE estimated from theory and assumingvNP = 0. The percentage of pores accessible to water increases from 55 to 78 as the pH is decreased from 7 to 2, due to a reversible change which is probably analogous to the reversible unfolding of the serum albumins. Supercontraction in LiBr produces a decrease in the specific volume of wool inn‐hexane, the partial specific volume in water, the pore volume, and the volume of pores inaccessible to water. Since analogous changes occur on denaturation of soluble proteins it is proposed that the crystalline regions (containing α‐helices) are less dense than the amorphous regions (containing random coils). This is probably due to poorer packing of the diverse side chains in the crystalline regions than in the amorphous regions, since in the latter the chains should be able to bend to accommodate bulky side chains. All evidence available on the accessibility of wool to various sorbates is summarized. Although it is not yet possible to be dogmatic, it is clear that the weight of evidence suggests that wool is approximately equally accessible to water and the lower alco
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