Geometric factor monolayer

The maximum isosteric differential heat of adsorption interpolated from the heat-coverage plots. c The roughness factor is defined as the ratio of the experimental values of the weight of adsorbate required for monolayer coverage to that calculated for the same coverage of a geometrically planar surface. It can be interpreted as the ratio of the real area to the apparent area of the adsorbent. 

The c (2 X 2) unit cell can also be written as (V2 x V2)i 45°. Here, the original unit vectors of the (1 x 1) stmcture have both been stretched by factors V2 and then rotated by 45°. Thus, sulfur on Ni (100) forms an ordered half-monolayer stmcture that can be labelled as Ni (100) + c (2x 2) -S or, equivalently, Ni (100) -i-(a/2 X V2) R45°-S. The c (2 x 2) notation is clearly easier to write and also easier to convert into a geometrical model of the stmcture, and hence is the favoured designation. 

The experimental evaluation of the adsorption from solution of amphiphilic materials at the solid-fluid interface usually involves the measurement of changes in the concentration of the adsorbed material in the contacting solution, for S/L interfaces, or the amount actually adsorbed onto the solid for S/V systems. The usual method for evaluating the adsorption mechanism is through the adsorption isotherm. The important factors to be considered are (1) the nature of the interaction between the adsorbate (the amphiphile) and the adsorbent (the solid) (2) the rate of adsorption (3) the shape of the adsorption isotherm and the significance of plateaus in it (4) the extent of adsorption (i.e., monolayer or multilayer formation) (5) the interaction of solvent, if present, with the solid surface (6) the geometric orientation of the adsorbed molecules at the interface and (7) the effect of environmental factors such as temperature, solvent composition, and pH on the adsorption process and equilibrium. 

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