Base

in chemistry, a compound formed by a metal and oxygen; also, sometimes, hydrogen. Certain other elements combined with oxygen and hydrogen, or with hydrogen alone, form acids. An acid and a base unite to form water and a salt. Thus sodium combines with oxygen and hydrogen to form a base known as sodium hydroxide; chlorine unites with hydrogen to form an acid known as hydrochloric acid. Both the base and the acid named are liquids. They may be combined to form common water and the white powder known as common salt. Acids are sour; bases are bitter, slimy to the touch, and corrosive; salts are soapy or salty to the taste. The chief base-forming metals are: aluminum, calcium, gold, iron, magnesium, mercury, platinum, potassium, silver, sodium, tin, and zinc. A base changes red litmus to blue. See Litmus; Acid; Salt; Alkali