The　experimental　errors　due　to　liquid-phase　adsorption　are　determined　by　comparing　the　equilibrium　concentration,　calculated　with　the　use　of　the　Freundlich　and　Langmuir　isotherms,　and　the　concentration　measured　in　experiments　under　equilibrium　conditions.　For　demonstrating　the　experimental　errors　the　detailed　original　data　of　certain　authors　are　cited.　The　experimental　errors　are　shown:　1)　for　determination　of　the　intraparticle　diffusivities　via　measuring　the　adsorption　kinetics　of　sodium　laurybenzenesulfonate　and　phenol　from　dilute　aqueous　solution　on　two　kinds　of　activated　carbon;　2)　for　determination　of　the　intraparticle　diffusivities　of　adsorbents　from　concentration　change　of　2-　dodecylbenzenesulfonate　on　four　different　activated　carbon　particles　via　pore　diffusion　and　rectangular　isotherm　assuming;　3)　for　determination　of　surface　transfer　via　measuring　the　adsorption　rate　over　the　range　of　25-　75°C　of　benzaldehyde　on　polymeric,　porous　amberlite　particles.