STABILITY OF COLLOIDAL SYSTEMS: Colloidal particles undergo frequent collisions as a result of Brownian motion. Whether these collisions result in coagulation (permanent contact or close aggregation of particle), flocculation (temporary contact or large aggregates) or whether the particles rebound and […]
A disperse system is defined as a heterogeneous two-phase system in which the disperse phase is distributed as particles or droplets throughout another phase called as dispersion medium. Based on the size of dispersed particles within the dispersion medium, the […]
PROPERTIES OF COLLOIDAL DISPERSIONS: Kinetic Properties: Brownian motion- Brownian motion describes the random zigzag movement of colloidal particles. Colloidal particles are subject to random collisions with the molecules of the dispersion medium; hence, each particle pursues an irregular and a […]
METHODS OF ADJUSTING TONICITY: The methods for adjusting tonicity subdivided into two classes: Class I methods, which employ sodium chloride or some other substance to the drug solution to lower the freezing point of the solution to – 0.52° and […]
PHARMACEUTICAL BUFFERS: Buffers are used to establish and maintain ion activity within narrow limits. The most common buffered systems in pharmacy are used: To establish hydrogen-ion activity for the calibration of pH meters. To prepare isotonic dosage form formulations. To […]
Buffers are substances or a combination of substances that, by their presence in solution, resist changes in pH upon the addition of small quantities of acid or alkali. Buffered solutions are necessary in many experiments conducted in pharmaceutical research. Drug […]
Physical Stability: It has already been noted that on purely thermodynamic grounds, emulsions are physically unstable. A reduction of the interfacial area by coalescence reduces the system’s energy, and this process is thermodynamically favoured. However, thermodynamic stability of emulsions differs […]
Theories of emulsification: Surfactant (Monomolecular adsorption): To reduce the interfacial tension Oil droplets are surrounded by a coherent monolayer of the surfactant which prevents coalescence. If the emulsifier is ionized, the presence of strong charge may lead to repulsion in […]
Emulsions are the mixtures of two or more type of liquids where, one is such as droplets, of tiny or even ultramicroscopic size, which are distributed throughout each other. These are usually formed from the component of liquids either in […]
Complexation Methods of Analysis: A determination of the (1) stoichiometric ratio of ligand to metal (or donor to acceptor) and the (2) stability constant for complex formation are important in the study and application of complexes. Several methods for estimation […]