DESCRIPTION OF THE NONIONIC ADSORPTION LAYER BY CUBIC EQUATIONS OF STATE

The van der Waals, Redlich-Kwong, Peng-Robinson and an equation of sta te derived by Smith were applied to approximate the run of surface pre ssure (pi) - area (sigma) curves of the adsorption layer of n-pentyl t o n-octyl ethers of tri- and tetraoxyethylene glycols. The equation pa rameters: excluded molar area (sigma(oi)) and an interaction energy te rm (a(i)) were determined by simplex method. The equations parameters were found to be related to the structure of the amphiphiles. The sigm a(oi) decreased with the length of alkyl chain and was nearly uniform for the equations of state in question except for Smith equation. The interaction energy in the adsorption layer calculated per methylene gr oup was in the range of ca. 0.29-0.43 RT, depending on the equation of state used.