Specific surface: The specific surface of a powder is defined as the surface area per unit volume (Sv) or per unit weight (Sw). SURFACE AREA DETERMINATION METHODS: The surface area can be determined directly by one of the following two […]
DERIVED PROPERTIES OF POWDERS: There are numerous derived properties that are based on fundamental properties. Those with particular relevance to pharmacy are discussed here. Packing geometry Porosity Density Bulkiness Flow property Packing Geometry: A set of particles can be filled […]
Density (Ƿ): Density is defined as weight per unit volume. Based on the types of volume defined, the corresponding ‘density’ may be proposed. Table 1 – Types of densities Density Dełnition Formula Determination Comment Bulk(Ƿb) Mass divided by bulk volume […]
A Pharmaceutical suspension is a coarse dispersion in which internal phase (therapeutically active ingredient)is dispersed uniformly throughout the external phase. The internal phase consisting of insoluble solid particles having a range of size(0.5 to 5 microns) which is maintained uniformly […]
SEDIMENTATION OF FLOCCULATED PARTICLES: When sedimentation is studied in flocculated systems, it is observed that the flocs tend to fall together, producing a distinct boundary between the sediment and the supernatant liquid. The liquid above the sediment is clear because even […]
WETTING OF PARTICLES: The initial dispersion of an insoluble powder in a vehicle is an important step in the manufacturing process and requires further consideration. owders sometimes are added to the vehicle, particularly in large-scale operations, by dusting on the […]
Electric double layer: Particles dispersed in a liquid medium may become charged in one of two main ways. Ionic species present in a solution may be adsorbed at the surface or, alternatively, charges on the surface may arise due to […]
The term ‘rheology’ was derived from the Greek words rheo (flow) and logos (science) and is used to describe the flow of liquids and the deformation of solids. Viscosity is an expression of the resistance of a fluid to flow: […]
Thixotropy: Thixotropy is defined as the progressive decrease in viscosity with time for a constant applied shear stress followed by a gradual recovery when the stress is removed. Thixotropy is a time-dependent shear thinning property. Thixotropy can be defined as […]