°C. The molecular weight of sodium chloride is approximately 58.4 grams per mole, so 58.4 grams of sodium chloride equals 1 mole. Since normal saline contains 9 grams of NaCl, the concentration is 9 grams per litre divided by 58.4 grams per mole, or 0.154 mole per litre. Since NaCl dissociates into two ions – sodium and chloride – 1 molar NaCl is 2 osmolar. Thus, NS contains 154 mEq/L of Na+ and the same amount of Cl−. This points to an osmolarity of 154 + 154 = 308, which is higher (i.e. more solute per litre) than that of blood (approximately 285). However, if the osmotic coefficient (a correction for non-ideal solutions) is taken into account, then the saline solution is much closer to isotonic. The osmotic coefficient of NaCl is about 0.93, which yields an osmolarity of 0.154 × 1000 × 2 × 0.93 = 286.44. Therefore, the osmolarity of normal saline is a close approximation to the osmolarity of blood. Usage For medical purposes, saline is often used to flush wounds and skin abrasions. However, research indicates that it is no more effective than potable tap water. Normal saline will not burn or sting when applied. Saline is also used in I.V. therapy, intravenously supplying extra water to rehydrate people or supplying the daily water and salt needs ("maintenance" needs) of a person who is unable to take them by mouth. Because infusing a solution of low osmolality can cause problems such as hemolysis, intravenous solutions with reduced saline concentrations (less than 0.9%) typically have dextrose (glucose) added to maintain a safe osmolality while providing less sodium chloride. The amount of normal saline infused depends largely on the needs of the person (e.g. ongoing diarrhea or heart failure). Saline is also often used for nasal washes to relieve some of the symptoms of rhinitis and the common cold. The solution exerts a softening and loosening influence on the mucus to make it easier to wash out and clear the nasal passages for both babies and adults. In very rare instances, fatal infection by the amoeba Naegleria fowleri can occur if it enters the body through the nose; therefore tap water must not be used for nasal irrigation. Water is only appropriate for this purpose if it is sterile, distilled, boiled, filtered, or disinfected. Sterile isotonic saline is also used to fill breast implants for use in breast