Introduction Solubility is defined in quantitative as well as qualitative term. In quantitative term solubility is defined as the concentration of solute in a saturated solution at a certain temperature, and in qualitative term, it can be defined as spontaneous interaction of two or more substances to form a homogeneous dispersion. Solubility is an intrinsic material property that can be altered only by chemical modification of the molecule.
The solubility of an agent in a particular solvent indicates the maximum concentration to which a solution may be prepared with that agent and solvent. Solubility is the property of a solid, liquid, or gaseous chemical substances which is called as solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous
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Hydrates/ solvates
The stoichiometric type of adducts where the solvent molecules are incorporated in the crystal lattice of the solid are called as the solvates. When the solvent in association with the drug is water, the solute is known as a hydrate. Generally the anhydrous form of drug has greater solubility than the hydrates. This is because the hydrates are already in interaction with water and therefore have less energy for crystal break-up in comparison to the anhydrous.
4. Temperature
If the solution process absorbs energy then the temperature is increased as the solubility will be increased. If the solution process releases energy then the solubility will decrease with increasing temperature. Generally, an increase in the temperature of the solution increases the solubility of a solid solute. For all gases, solubility decreases as the temperature of the solution increases.
5. Pressure
For gaseous solutes, solubility is increases with the application of presser. For solids and liquid solutes, changes in pressure have nearly no effect on solubility.
6. Molecular size
The larger the molecule or the higher its molecular weight the less soluble the substance.
7. Nature of