410 results provide a general confirmation of the conclusions reached in the preceding papers of this series . Acknowledgment. The authors acknowledge the assistance of John S. Mason in the determination of sol fraction, gel fraction, and distention index; Ines V. I deGruy in the electron micrographic analyses; and George I. Pittman in the preparation of the line drawings. _ . of Reagent Residues in Cotton Cellulose Modified with tris(1-Aziridinyl)phosphine Oxide, Textile Res. J . 40, 395-400 (1970).ABSTRACT A more reproducible method for determining the swelling of wool fibers is suggested. It has been shown that high concentrations of urea do not increase the swelling of wool in cold aqueous solution. The influence of the addition of small amounts of sodium metabisulfite and wetting agents on the swelling of wool in urea solutions is discussed. It has been shown that small amounts of surface protein material are removed from the wool by concentrated urea solutions. The reported presence of a amino adipic acid in the surface material has been confirmed and over-all analysis of the ureasoluble material indicates its similarity with a previously isolated cuticular sheath fraction. The implications of these findings in relation to wool processing are discussed.

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The causes of anomalous results obtained in the measurement of the swelling of wool fibres by different methods have been investigated. The British Standard method (BS 2043) and the fixed‐point method were examined. When urea solutions are used as the swelling media, the results obtained by the two methods differ considerably. The short lengths of fibre used in the BS 2043 method are well within the fibre dimensions for swelling to occur by end penetration and hence give results that can be misleading when related to the swelling of undamaged fibres during processing. When the swelling agent itself can penetrate the fibre wall, either method will give reliable results. When, however, the agent can show colligative osmotic properties typical of many non‐volatile salts, discrepancies may arise between the two methods.

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