The Production of Unshrinkability by Cross‐linkage Formation in Wool

When Lincoln wool and human hair fibres are treated with a solution of mercuric acetate (0·1 m ) in acetic acid (0·1 n ), the increase in the resistance of the fibres to deformation is a linear function of the square root of the time of treatment, except in the initial stages. Determination of the slopes of the lines has shown that the rate of diffusion of mercuric acetate into Lincoln wool is 2·2 times as fast as into the human hair, in general agreement with earlier observations 7 on the rate of diffusion of Acid Orange 26 into 56s Down wool and human hair at 60°c. and p H 2·04. Since, in addition, Lincoln wool fibres are finer than those of human hair, i.e. since the ratio of surface to mass is greater, the elastic properties of Lincoln wool fibres are modified far more rapidly than those of human hair by treatment with mercuric acetate. In agreement with these observations, the rate at which Lincoln wool fibres are penetrated by mercuric acetate, as determined by staining the treated fibres in a solution of hydrogen sulphide and preparing cross‐sections, has been shown to be far greater than in the case of human hair. These results serve to explain why, in a previous paper 3 , the elastic properties of human hair fibres were found to be only slightly altered under conditions which made an all‐wool flannel unshrinkable. Since it has also been shown that there is a smooth relationship between the milling shrinkage of treated patterns and the extent to which the fibres are penetrated by mercuric acetate, as observed in stained cross‐sections, there can be no doubt that mercuric acetate makes wool unshrinkable by modifying the elastic properties of the fibres.