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Laboratory methods

H is produced in labs, often as a by-product of other reactions. Many metals react with water to produce H, but the rate of hydrogen evolution depends on the metal, the pH, and the presence of alloying agents. Most often, hydrogen evolution is induced by acids. The alkali and alkaline earth metals, aluminium, zinc, manganese, and iron react readily with aqueous acids. This reaction is the basis of the Kipp's apparatus, which once was used as a laboratory gas source:

In the absence of acid, the evolution of H is slower. Because iron is widely used structural material, its anaerobic corrosion is of technological significance:

Many metals, such as aluminium, are slow to react with water because they form passivated oxide coatings of oxides. An alloy of aluminium and gallium, however, does react with water. At high pH, aluminium can produce H:

Some metal-containing compounds react with acids to evolve H. Under anaerobic conditions, ferrous hydroxide (Fe(OH)) can be oxidized by the protons of water to form magnetite and H. This process is described by the Schikorr reaction:

This process occurs during the anaerobic corrosion of iron and steel in oxygen-free groundwater and in reducing soils below the water table.