![]() ![]() Water is the dispersed phase and oil is the dispersion medium. Water in oil (W/O) emulsions: The internal phase is composed of water droplets and the external phase is nonaqueous. Oil is the dispersed phase and water is the dispersion medium.Ģ. Oil in water (O/W) emulsions: The oil (internal or dispersed) phase is dispersed as droplets throughout the aqueous phase (external or continuous phase or dispersion medium). Examples are liquid paraff in emulsion, cod liver oil emulsion.ġ. Emulsions enhance the rate and extent of absorption through the alimentary canal, improve the solubility of poorly water-soluble drugs, and can prolong drug action. It also improves penetration and spreadability. It improves the taste of objectionable medicinal agents and makes them more acceptable. Emulsion increases the stability of many drugs that are unstable in an aqueous solution. The liquid droplets are generally known as the dispersed phase or internal phase, whereas the liquid in which they are dispersed is known as the continuous phase, dispersion medium, or external phase. The stability of the emulsion is increased by adding another substance known as the emulsifying agent or emulsifiers. Such a system possesses minimal stability because the droplets quickly coalesce and the two liquids get separated. The following are the disadvantages of using emulsions as dosage forms:Įmulsion is a heterogeneous system consisting of one immiscible liquid dispersed in another in the form of droplets whose diameter, in general, exceeds 0.1 microns.Advantages and Disadvantages of emulsions as Dosage forms.Dialysis takes advantage of the fact that colloids cannot diffuse through semipermeable membranes to filter them out of a medium. The larger dispersed particles in a colloid would be unable to pass through the membrane, while the surrounding liquid molecules can. It is however reflected in all directions when it passes through the milk, which is colloidal.Īnother method of determining whether a mixture is a colloid is by passing it through a semipermeable membrane. The light is not reflected when passing through the water because it is not a colloid. Figure 2: Light being shined through water and milk. The beam of light can be easily seen because the fog is a colloid. An example of this is shining a flashlight into fog. When light is shined through a true solution, the light passes cleanly through the solution, however when light is passed through a colloidal solution, the substance in the dispersed phases scatters the light in all directions, making it readily seen. Table 1: Examples of Colloids Dispersion MediumĪn easy way of determining whether a mixture is colloidal or not is through use of the Tyndall Effect. A common use of hydrocolloids is in the creation of medical dressings. For example, Jello powder mixed in with water creates a hydrocolloid. The particles in the dispersed phase can take place in different phases depending on how much water is available. When the dispersion medium is water, the collodial system is often referred to as a hydrocolloid. Aerosol contains small particles of liquid or solid dispersed in a gas.įigure 1: Examples of a stable and of an unstable colloidal om Wikipedia.Foam is formed when many gas particles are trapped in a liquid or solid.Sol is a colloidal suspension with solid particles in a liquid.The types of colloids includes sol, emulsion, foam, and aerosol. If the dimensions are smaller than this the substance is considered a solution and if they are larger than the substance is a suspension.Ī common method of classifying colloids is based on the phase of the dispersed substance and what phase it is dispersed in. This can be more precisely quantified as one or more of the substance's dimensions must be between nanometers. To be classified as a colloid, the substance in the dispersed phase must be larger than the size of a molecule but smaller than what can be seen with the naked eye. The substance being dispersed is referred to as being in the dispersed phase, while the substance in which it is dispersed is in the continuous phase. In colloids, one substance is evenly dispersed in another. ![]() These are also known as colloidal dispersions because the substances remain dispersed and do not settle to the bottom of the container. A colloid is a mixture that has particles ranging between nanometers in diameter, yet are still able to remain evenly distributed throughout the solution. \)Ī colloid is one of the three primary types of mixtures, with the other two being a solution and suspension. ![]()
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