Hydrogen compounds are only required to contain carbon. However, most of them also contain hydrogen, and because it is the carbon-hydrogen bond which gives this class of compounds most of its particular chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. Millions of hydrocarbons are known, and they are usually formed by complicated synthetic pathways that seldom involve elementary hydrogen. Compounds of hydrogen are often called hydrides, a term that is used fairly loosely. The term "hydride" suggests that the H atom has acquired a negative or anionic character, denoted H, and is used when
Hydrogen storage temperature for a given partial pressure. The Italian catalyst manufacturer Acta has proposed using hydrazine as an alternative to hydrogen in fuel cells. As the hydrazine fuel is liquid at room temperature, it can be handled and stored more easily than hydrogen. By storing it in a tank full of a double-bonded carbon-oxygen carbonyl, it reacts and forms a safe solid called hydrazone. By then flushing the tank with warm water, the liquid hydrazine hydrate is released. Hydrazine breaks down in the cell to form nitrogen and hydrogen which bonds with oxygen, releasing water. Silicon hydrides and germanium hydrides are