TYPES OF EMULSIONS

An emulsion may be prepared from any two immiscible liquids but in pharmacy one phase is usually water.

Oil in water emulsions

These consist of oil droplets dispersed throughout an aqueous continuous phase.

Examples:

Medicinal emulsions mostly for oral use

Rubber latex

Egg yolk

Milk

Vanishing creams

Water in oil emulsions

These consist of water dispersed throughout a continuous oil phase

Examples:

Oily calamine lotion

Hydrous ointment

Cold creams

Multiple Emulsions

It is possible to prepare oil in water emulsion in which water globules are dispersed within the oil globules so that the system may be designated as water in oil in water

Medicinally used emulsions for oral administration are usually oil in water type and require oil in water emulsifying agent. These include synthetic non-ionic surface active agents, acacia, gelatin and tragacanth.

Externally applied emulsions may be oil in water or water in oil. Intravenous emulsions may be oil in water while intramuscular emulsions are water in oil or oil in water.

Water in oil emulsions are used almost exclusively for external application and may contain one or several of the following emulsifiers such as calcium palmitate, spans, cholesterol wool fat.

EMULSIONS

Definition:

An emulsion is a system of two immiscible phases, one of which is dispersed as fine globules throughout the other.

Emulsions may also be defined as a thermodynamically unstable system of at least two immiscible liquid phases, one of which is dispersed as globules in other liquid phase, stabilized by presence of emulsifying agent.

The liquid phase that is subdivided is termed the dispersed phase and the other liquid surrounding the globules is the continuous phase.

Emulsion is stabilized by adding emulsifying agent.

Dispersed phase or continuous phase may consist of mobile liquids or semisolids, so emulsified systems include lotions, creams ointments.

Particle of globules size may generally extend from about 0.1 to 10 micron.

DEFINITION OF pH

Definition of pH:

pH is defined as the negative log of the hydrogen ion concentration, or pH = -log [H+]. pH may be an abbreviation of power of hydrogen or more explicitly the power of hydrogen ion concentration The pH scale commonly ranges from 0 to 14, which denotes a measure of the alkalinity or acidity of a solution. The pH scale is equal to 7 numerically for the neutral value of pH. An increase in the numerical value above 7 denotes an increase in alkalinity, while a decrease in the value below 7 shows an increase in the acidity of the solution.