91—the Chemical Action of Carrotting Agents on Fur

The work described shows that the only chemicals that are effective as carrotting agents are those which break the cystine linkages of rabbit hair. It is, however, immaterial whether the cystine linkages are broken by oxidation or reduction. Rupture of peptide linkages, salt linkages or hydrogen bonds without cystine bond rupture causes no improvement in the felting power of rabbit hair. Experiments on un-carrotted rabbit hair have shown definite differences between the tip and the shaft (i.e., the lower end of the fibre, without the actual root): the tip exhibits higher alkali- and acid-solubilities and higher swelling power than the shaft. These differences in chemical parameters are further increased by the process of carrotting. At the same time, the frictional resistance* of the carrotted hair is increased, between three and five times, and the work of extension is reduced. Determinations of the amine nitrogen of carrotted rabbit hair show that there also takes place in carrotting an N→O acyl transfer, similar to that shown by Zahn in carbonized wool.