The solubility of a compound may be increased by complexing it with a complexing agent. When an insoluble compound forms a complex that is more soluble in a solvent, the total solubility is equal to the inherent solubility of the uncomplexed drug and the concentration of the drug complex in solution. When a drug is mixed with water, some amount will get dissolved while some amount will remain undissolved. If a complexing agent is added to it, some quantity of the drug will get complexed and become soluble in water and the total solubility will be increased. When the amount of complexing agent added is increased, total solubility will increase; at a certain concentration of complexing agent, the solution will become saturated with respect to the free drug and the complex. After this point, further addition of complexing agent will form complex and the excess complex will be precipitated. When no drug is left for complexation, complexes of higher order may be formed. For example, iodine is sparingly soluble in water. However in the presence of potassium iodide, it forms a poly-iodide complex, which is completely soluble in water.