Pharmacy Study Material

Free pharmacy material Particle Size Analysis INTRODUCTION Particle size is the physical property of the compound which influences the stability, solubility and processability. The unit for the particle size is micrometer (μm). There are different methods for the determination of the particle size, as follows: Microscopy Sieving method Sedimentation method Sensing zone method Light scattering method Surface area measurement method The selection of the method is mainly based upon the following: Nature of the compound Solubility Toxicity Flowability Cost Specifcation requirements, etc. Types of Diameters Martin's diameter: This is the length of the line which bisects the particle. Feret's diameter: this is the distance between the two tangents of the particle. Projected area diameter: this is the diameter of the circle having the same area as that of the particle. METHODS FOR PARTICLE SIZE ANALYSIS Microscopy T...

Free pharmacy material Surface Tension Determination INTRODUCTION Surface tension is a phenomenon in which the surface of the liquid is in contact with the gas. Surface tension is defined as the force acting at right angles to a line of unit length present in the surface. This is denoted by ‘γ’. W = F × d where W = work; F = force; d = distance. Therefore, (γ) Gamma = F / d The SI units for the surface tension are newton/meter or dyne/cm. At a liquid surface, the molecule is not completely surrounded by other molecules. Surface tension phenomenon The surface tension of a liquid is the energy required to increase the surface area which increases the stability of the solution and increases the solubility rate. Examples of surface tension are drops of water, insects walking on water and paper clips floating on water. An important measure for the characterization of surfactants which reduces surface tension is the critical micelle co...