Simple Pharmanotes

  Principle: It's a “Tumbling Mixer”. It works on the mechanism of Diffusive Mixing. Construction:  Also called “Twin Shell Blender”. It consists of two vessels which are attached at the ends at 70 to90 degree angle as shown in the figure. It is made up of stainless steel or complete plastic. The blender is mounted on a metal frame on which it can be rotated. Sometimes baffles are attached inside for thorough mixing. The openings are used as inlet ports while it is unloaded through the discharge port at the bottom. Working: The materials to be mixed are introduced to the mixer through one of the ports. The mixer is loaded approximately two thirds of the volume to allow tumbling of the powders. When the mixer is started, it rotates along the axis and when the V is inverted, the material splits into two portions and undergoes tumbling. The tumbling movement during rotations causes mixing. The speed of the mixer plays an important role in the mixing, If rotations are slow: Mixing will

  Principle: It's a “Tumbling Mixer”. It works on the mechanism of Diffusive Mixing. Construction:  It consists of a vessel with conical ends as shown in the figure. All the contact parts are made up of stainless steel. The vessel is mounted on a metal frame on which it can be rotated. Working: The materials to be mixed are introduced to the mixer through one of the ports. The mixer is loaded approximately two thirds of the volume to allow tumbling of the powders. When the mixer is started, it rotates along the axis. The tumbling movement during rotations causes mixing. The speed of the mixer plays an important role in the mixing, If rotations are slow: Mixing will not take place as materials will just glide over one another. If rotations are very fast it will cause generation of centrifugal forces hence powders will remain adhered to the walls and hence no mixing will take place. For better results the double cone blender needs to be operated at an optimum speed. Uses: For mixing

  Definition Mixing is defined as an unit operation in which two or more components are treated in such a way  that each particle / molecule of the components lies as nearly as possible in contact with a particle / molecule of the other components . If this is achieved it produces a theoretical ‘ideal’ situation, called a perfect mix . Mechanisms of mixing: Mechanisms of Solid Mixing: Solids are mixed using three mechanisms as follows, Convective Mixing. Shear Mixing. Diffusive Mixing . Convective Mixing: Also called “ Macromixing ”. Involves transfer of a group of particles from one part of a powder bed to another part . Shear Mixing: Formation of shear forces by using an agitator arm or a blast of air causes movement of particles. Diffusive Mixing:  Also called “ Micromixin g”. Involves distribution of particles over a newly formed surface. In this the material is tilted causing the upper surface to come down due to gravity while smaller particles diffuse to the upper layer. Mechan

  Definition Mixing is defined as an unit operation in which two or more components are treated in such a way  that each particle / molecule of the components lies as nearly as possible in contact with a particle / molecule of the other components . If this is achieved it produces a theoretical ‘ideal’ situation, called a perfect mix . Objectives of mixing: To make simple physical mixture Physical change Dispersion Promotion of reaction. To make dispersions. To achieve uniformity in the composition of a product. Types of Mixtures Mixtures may be divided into three types that differ in their behavior as, Positive Mixtures . Negative Mixtures . Neutral Mixtures . Positive mixtures: Positive mixtures are formed from materials such as gases or miscible liquids, which mix spontaneously and irreversibly by diffusion and tend to approach a perfect mix.  There is no input of energy required.  In general, such materials do not present any problems in mixing . e.g. Mixing of sodium chloride