28—The Crystalline/Amorphous Ratio of Keratin Fibres

The proportion of disordered (amorphous) material in wool may be assessed by exposing a sample of known dry weight to saturated deuterium oxide vapour and expressing the gain in dry weight, duo to the hydrogen deuterium exchange reaction, as a fraction of the maximum possible gain in weight, calculated from the constitution on the assumption of complete accessibility to deuterium oxide. Using this procedure, the order of accessibility of three wools and mohair has been shown to be the same as that given by the Hailwood-Horrobin analysis of their water-adsorption isotherms, but the exchange reaction gives very much higher value , ranging from 0.87 for Lincoln wool to 0.82 for mohair, for the fraction accessible to heavy water. The exchange reaction has been used also to reveal differences in accessibility of the various types of fibre present in Now Zealand Lincoln hogget’s wool fibres (sickles) from the first follicles to develop being the most crystalline and those (histerotrichs) from the last follicles to develop being the least crystalline.