466 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS variations of the 20• index (i.e. the work required for the stretching of keratin fibres to 205/o of their original extension) in alcohol-water mixtures (39), T s could be replotted in accordance with equation (III). A linear relationship was obtained with an intercept Ts ø = 250øC (Fig. 15). 2.40 •_o 2.20 x o• o o 2.00 1 0.02 0.04 O.OG 0.08 I,+,•,ol Log L'+•J ---'- FigureIS. PlotofTsagainst log(1-FK•a) 1 + K•a Similarly when the retractive force of wool at 20•o extension and 25øC was plotted against log ({ + K•a• + Kaa] using Astbury and Street data (2), a linear relationship was obtained (Fig. 16). Equation (IV) also represents adequately the temperature dependence on the retractive force of hair fibres immersed in water as measured by Bull (41). A plot off, the retractive T force, against (1 - Ts•-7) using the values of T• ø = 210øC gives a linear plot (Fig. 17). From the slopes of Figs. 16 and 17 the values of AL and AH can be calculated as AL = 0.7 cm g4 and AH = 20 J g4. The latter value is in good agreement with the heat of shrinkage determined by means of D.T.A. experiments (42) (AHo = 16.8 J g4. The values AHo and AL determined from the slopes of the curves in Figs. 16 and 17 are partial specific heat and length changes occurring during the melting of 1 g of hair. On the other hand the slope of the curve in Fig. 15 represents the partial molal heat change which accompanies the

THE BINDING OF SMALL MOLECULES TO HAIR--I 467 • 20 30- o i i 0.05 O.lO Log U Figure 16. Plot off against log , 1 +K•.a 3.0 -- --b o o , 'u- 25% extension • 8% extension I I 0.50 0.35 0.40 [,_% --,.. Figure 17. Plot off as a function of (1 - TITsø).