![]() ![]() Thus, a eutectic mixture can melt at a temperature lower than the temperature required to melt either of the individual components. It is very important because the eutectic point is at a temperature lower than the melting point of either of the individual components. A phase diagram is used to establish the ‘eutectic point’ at which the solid and liquid phases exhibit the same composition. A two component system consisting Salol-thymol system shows four regions in the phase diagram, information such as the melting point of Individual components can be established. For two component systems like Water and phenol, which are partially miscible, the phase diagram gives the information regarding the various concentrations at which the two phases are miscible with each other and the temperature at which they are miscible. As per phase rule equation, a one component system should have maximum two degrees of freedom. 4įor one component system such as water, the phase rule is enforced and the phase diagram gives a batch of information like the sublimation temperature, triple point, boiling and freezing temperature. ![]() For example, in a three component system with two phases, degree of freedom will be one or the system is will be univariant. The system can be called as in-variant, uni-variant, bi-variant and so on as per to degrees of freedom (F) is zero, one, two and so on. Phase diagrams can be defined as graphical representation consist of area curve, lines and points which are used to show several conditions such as temperature and pressure at which thermodynamically distinct phases occur, transform from one phase to another and coexist at equilibrium. The phase rule is applied to define a system composed of single component as well as multi-component. Here, the F is the number of degrees of freedom in system or the minimum numbers of factors that have to be known to define a system, C is the number of independent components or parts of a system and P is the number of phases present in the system. Mathematically, it can be written as F = C – P + 2 Phase rule can be defined as ‘When a heterogeneous system in equilibrium at a definite temperature and pressure, the number of degrees of freedom is equal to by 2 the difference in the number of components and the number of phases provided the equilibrium is not influenced by external factors such as gravity, electrical or magnetic forces, surface tension etc. The phase rule is based on thermodynamics and helps to determine the condition for non-reactive multi-component heterogeneous or polyphase system to exhibit phase equilibrium. The phase rule was given by J.W Gibbs in 1874. To define a particular system or state of each phase in a system, a fixed number of variables have to known. All the parts of a system can be termed as components. The review focuses on the concept of phase diagram and phase rule, various methods and rules relating to ternary phase diagrams, various examples and its recent applications in pharmaceutical research.Ī phase can be described as chemically homogeneous and physically discrete part or portion of a system that is separated from other parts or portions of a system by boundaries. Ternary phase diagrams give the precise and accurate data of the various composite component systems and are utilized in several areas of pharmaceuticals like the formulation of various dosage forms, polymer coating methods and several other formulation processes. A ternary phase diagram has the shape of a triangular prism with an equilateral triangle as a foundation which is used to describe a three component system. A phase diagram is a graphical representation composed of area curve, lines and points, which is used to describe a specific system composed of a single or multiple components and generate the data with respect to concentration of different components, temperature and pressure at which thermodynamically distinct phases occur, transform from one phase to another and coexist at equilibrium. Phase diagram serves as an important tool for screening of such formulation components. Various pharmaceutical formulations such as emulsion, micro emulsions and gels are mainly composed of lipid soluble component, water soluble component, surfactant and cosolvents. The phase rule given by J.W Gibbs in 1874 is applied to define a system composed of single component as well as multi-component. A phase is a physically discrete and chemically homogeneous portion of a system, separated by boundaries from other portions of the system. ![]()
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