constant for benzoic acid (1/n = 0.2) and isin the range (0.15 -0.6) for acetic acid.These ranges of Freundlich parameterequation values 1/n (0.19 - 0.5) have beenalready obtained [20] and shown that thesurface is not heterogeneous. Acetic andbenzoic acids values from Langmuir Xmand b are represented (Table 1). For aceticacid, am and b respectively decreases andincreases with temperature, but for benzoicacid, am is a constant (2 mmol/g) and bseems to be decreasing. The observation ofk value has shown a higher capacity ofadsorption for benzoic rather than foracetic acid. We can claim that theformation of apparent monolayer coverageonto carbon surface to the both adsorbentsis not reached. It can be expected thatapparent monolayer coverage wouldhappened at higher adsorbateconcentrations. These types of isotherms inwhich the saturation of the surface has notbeen reached, due to experimentaldifficulties can be classified as L1isotherms [7]. These isotherms are similarto those obtained by other authors duringadsorption at different temperatures oversolid surfaces [21]. They could beinterpreted as isotherms resulting ofphysical adsorption in the micro poroushaving molecular dimensions. In this case,the Langmuir isotherm usually predictsbetter the adsorption behaviour than theexponentially increasing Freundlichisotherm [22].The results enable us to trace the functionlnb according to 1/T and to obtain a line ofequation: lnb= - ΔH°/RT + ΔS°/R (R:noble gas constant, T: temperature (K))Thus, we could determine the enthalpy ofadsorption (ΔH°) and entropy ofadsorption (ΔS°).For benzoic acid: ΔH° = -53.62 KJ/moland ΔS° = -90.84 J/mol.K.For acetic acid: ΔH° = -26.25 KJ/mol andΔS° = -1.20 J/mol.K.