Manganese oxide is also called as manganese dioxide. It is derived from manganese, a brittle metal element. It is widely distributed in the earths crust, and is essential in steel making. The element is needed for plant growth and in the physical development of higher animals. Manganese is involved in reducing the levels of nitrates in green plants. Lack of manganese causes testicular atrophy in animals. However, too much in either plants or animals is toxic. The principal use for MnO2 is for dry-cell batteries, such as the alkaline battery and the zinc-carbon battery. MnO2 is also used for production of MnO4-. It is used extensively as an oxidising agent in organic synthesis. Manganese dioxide is also used as a reagent in organic chemistry for the oxidation of benzylic alcohols.