An investigation was made of the temperature dependence of the ellipsometric parameter DELTA at the liquid-vapor boundary close to the critical stratification point of binary solutions of methanol-n-hexane and nitrobenzene-n-hexane. For the critical composition the authors established an increase in the parameter DELTA due to the increase in the thickness of the surface layer in the form DELTA approximately epsilon ** minus **y, where epsilon is the relative deviation of the temperature from the critical temperature, the exponent is y approximately equals 0. 35 plus or minus 0. 15. On the basis of the result obtained, the authors have analyzed the laws for the increase in surface layer thickness and adsorption at the indicated boundary.