CATIONIC-ANIONIC INTERACTIONS 353 RESULTS AND DISCUSSION The uptakes of the cationic surfactant CP-6 by untreated wool and by wools that had been treated with SDS are shown in Figures 1 and 2. The uptake of CP-6 on the untreated wool is almost complete in 60 min at 60øC (Figure 1). The initial uptake of CP-6 is faster when the wool contains either 0.5 or 1.0% of SDS, but on prolonged treatment the cationic then desorbs from the 1.0% sample but not the 0.5% sample. When wool contains 5.0% of SDS, much lower initial sorption of CP-6 is observed, lOO 80 60 40 20 pH 7, 60 ø 0 0 20 40 60 treatment time (minutes) +0.0 % [] 0.5 % '•' 1.0 % +5.0 % Percent anionic surfactant (SDS) pretreatment Figure 1. % Uptake cationic CP-6 (1.0% applied).

354 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS lOO 80- 6O 40 20 OJ I I pH 7, 60 ø I 0 20 40 60 treatment time (minutes) •0.2 % •0.5 % [] 1.0 % Percent cationic surfactant (CP-6) applied 0.5% anionic surfactant (SDS) pretreatment Figure 2. % Uptake cationic CP-6. presumably because it reacts rapidly with the large amount of SDS present on the wool. However, even in this case, further desorption occurs after 20 min. For wool pretreated with 0.5% SDS, sorption of CP-6 followed by desorption is observed with 0.2% and 0.5% applications of CP-6 but not with 1.0% CP-6 (Figure 2). The sorption/desorption phenomenon is observed only when the amount of cationic surfactant applied is not greater than the amount of anionic surfactant initially on the