Hydrophilic–Lipophilic Balance Concept: The HLB concept was introduced by Griffin in 1947 to classify nonionic surfactants but has since been applied to ionic surfactants as well. In this system, each surfactant is assigned a number between 1 and 20, representing […]
Many attempts have been made to develop a mathematical expression that relates the amount of the adsorbate per unit weight of adsorbent to a function of the solute concentration remaining in the solution at a fixed temperature. The most frequently […]
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 […]