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The wetting of cotton skeins by aqueous solutions of individual surfactants of structure C12H25(OC2H4)XOH, where x = 4‐8, with homogeneous head groups, and of a Poisson distribution mixture containing an average of 5.5 oxyethylene groups, has been measured at various temperatures using the Draves technique. An individual compound with a homogeneous polyoxyethylene head group is a more effective wetting agent than a Poisson distribution mixture with the same average number of oxyethylene units. Loglog plots of wetting time vs surfactant concentration are linear in the concentration range of 0.25 to 1 g/L. The best wetting agents at any temperature have slopes in the ‐1.5 to ‐1.6 range and Y‐intercepts from +0.6 to +0.7. Wetting in these systems appears to be diffusion‐controlled. The wetting time at 1 g/L concentration is a measure of the wetting effectiveness of the surfactant, because it is roughly inversely proportional to the diffusion constant of the surfactant at that concentration. For materials 30 C or more below their cloud point, temperature increase causes an increase in wetting effectiveness. As the cloud point of the surfactant solution is approached, however, both the slope and the Y‐intercept of the log‐log plot of wetting time vs surfactant concentration change sharply. The absolute value of the negative slope decreases and the positive value of the Y‐intercept increases, resulting in greatly reduced wetting effectiveness.

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