Acid salts are a type of salt formed when an acid reacts with a base, but not all of the acidic hydrogen ions are replaced by metal ions. They contain both acidic and basic properties, which means they can act as either acids or bases in chemical reactions. Common examples include sodium bicarbonate and potassium hydrogen tartrate. These salts typically have a pH less than 7, indicating their acidic nature. Acid salts are often used in cooking, baking, and various industrial applications. Their unique properties make them useful in buffering solutions and controlling pH levels in different environments.