BET isotherm: Langmuir and Freundlich isotherms are based on the formation of a saturated monolayer of the adsorbate on the surface of the adsorbent. The BET isotherm assumes that a multimolecular layer of adsorbate molecules covers the surface of the […]
ADSORPTION PHENOMENA: Adsorption is the process in which materials of one phase (adsorbate) accumulate or concentrate at the interfacial surface of the other phase (adsorbent). It is a spontaneous phenomenon driven by a reduction of the surface free energy. Adsorption […]
Spreading Coefficient (S): In general, spreading of a liquid occurs when the work of adhesion between two liquids exceeds the work of cohesion between the molecules of each liquid. Work of adhesion (Wa)- Consider a liquid drop with surface tension […]
Ring Detachment Method (du Nouy tensiometer): The du Nouy’s ring method is similar to the Wilhelmy plate method, but it uses a ring or loop of wire. A platinum or Iridium wire of ~4 cm in circumference is suspended from […]
Drop Weight and Drop Count Method: Principle: If a liquid is allowed to fall slowly through a capillary tube, the liquid first forms a drop at the tip of the capillary tube, which gradually increases in size and finally detaches […]
Capillary Rise Method: The capillary rise method is considered to be the most accurate way of measuring surface tension as the surface of the liquid is undisturbed during the measurement. However, the method is not suitable for measuring the interfacial […]
Interface is the boundary between two or more phases exist together. Several types of interface can exist depending on whether the two adjacent phases are in solid, liquid or gaseous state. LIQUID INTERFACES : Surface and Interfacial Tensions In the liquid […]
Sedimentation Technique: Equivalent diameter: Stokes’ diameter; frictional drag diameter—a sphere having an equivalent drag force to a particle of the same diameter in the same fluid at the same velocity. Range of analysis: 1 μm to about 200 μm. It […]
Dielectric constant: To properly discuss dipoles and the effects of solvation, one must understand the concept of dielectric constant. Placing a molecule in an electric field is one way to induce a dipole. In a capacitor (condenser), there are two parallel […]
A phase is the part whose physical and chemical properties are completely equal and homogenous. it is separated from other parts of the system by interfaces. A system containing water and its vapor is a two-phase system. An equilibrium mixture […]