Potassium is a very significant body mineral, important to both cellular and electrical function. It is one of the main blood minerals called "electrolytes" (the others are sodium and chloride), which means it carries a tiny electrical charge (potential). Potassium is the primary positive ion (cation) found within the cells, where 98 percent of the 120 grams of potassium contained in the body is found. The blood serum contains about 4-5 mg. (per 100 ml.) of the total potassium; the red blood cells contain 420 mg., which is why a red-blood-cell level is a better indication of an individual's potassium status than the commonly used serum level.