Chloride (Cl–), an anion found in the blood, works together with sodium to help maintain oncotic pressure and water balance in the body. Chloride is inversely related to bicarbonate levels in the blood. Chloride is also part of hydrochloric acid (HCL) which is utilized in the stomach to breakdown food. When Red Blood Cells (RBCs) take up CO2 they take up chloride as well. The negative ion bicarbonate then leaves the red blood cell so that the electrical charge is maintained. Extra chloride is excreted into the urine by the kidneys.