Saline is a solution made of sodium chloride and water and has many uses in medicine. Intravenous injection of saline is used to treat dehydration in patients. It is also used to dilute other medications given by injection. Sodium chloride in the solution replenishes the electrolytes. The rate at which the solution is administered depends on the condition of the patient. It is very important to maintain the concentration of the saline solution otherwise it will result in adverse effects.  This chapter describes components of solutions and quantitative analysis of solution concentration.