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Isotherm may refer to: . Isotherm (contour line) – a type of equal temperature at a given date or time on a geographic map Isotherm – in thermodynamics, a curve on a P-V diagram for an isothermal process
An isothermal process is a type of thermodynamic process in which the temperature T of a system remains constant: ΔT = 0. This typically occurs when a system is in contact with an outside thermal reservoir, and a change in the system occurs slowly enough to allow the system to be continuously adjusted to the temperature of the reservoir through heat exchange (see quasi-equilibrium).
The Gibbs adsorption isotherm for multicomponent systems is an equation used to relate the changes in concentration of a component in contact with a surface with changes in the surface tension, which results in a corresponding change in surface energy.
Classification of Sorption Isotherms by Brunauer Type I through V. He found that Type II and Type III isotherms require highly porous materials or desiccants, with first monolayer adsorption, followed by multilayer adsorption and finally leading to capillary condensation, explaining these materials high moisture capacity at high relative humidity.
Various types of graphs in thermodynamics, engineering, and other sciences use isobars (constant pressure), isotherms (constant temperature), isochors (constant specific volume), or other types of isolines, even though these graphs are usually not related to maps. Such isolines are useful for representing more than two dimensions (or quantities ...
The linear isotherm can be used to describe the initial part of many practical isotherms. It is typically taken as valid for low surface coverages, and the adsorption energy being independent of the coverage (lack of inhomogeneities on the surface). The Henry adsorption constant can be defined as: [2]
Isotherms of real gas Dark blue curves – isotherms below the critical temperature. Green sections – metastable states. The section to the left of point F – normal liquid. Point F – boiling point. Line FG – equilibrium of liquid and gaseous phases. Section FA – superheated liquid. Section F′A – stretched liquid (p<0).
This isotherm takes into account indirect adsorbate–adsorbate interactions on adsorption isotherms. Temkin [17] noted experimentally that heats of adsorption would more often decrease than increase with increasing coverage. The heat of adsorption ΔH ad is defined as