Active hydrogen

This refers to hydrogen that has become more susceptible to chemical reactions when the stable bonds of hydrogen molecules are broken by exposure to ultraviolet light or discharge, generating atomic hydrogen. This includes hydrogen in the so-called nascent (machine) state, and highly reactive hydrogen on metals such as palladium and nickel that act as catalysts for hydrogenation. It exhibits a strong reducing effect. When atomic hydrogen is sprayed onto a metal surface, it can reach a high temperature of 4000°C when it returns to hydrogen molecules, and since it does not rust the metal, it is used for welding, etc.

[Kenichi Morinaga]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

紫外線照射、放電などにより水素分子の安定な結合が切れて、原子状態の水素を生じ化学反応をおこしやすくなった水素をいう。いわゆる発生期（機）状態の水素や、パラジウム、ニッケルなど水素添加の触媒となる金属上の反応性に富んだ水素もこれに含まれる。強力な還元作用を示す。原子状水素を金属表面に吹き付けると、水素分子に戻る際4000℃の高温が得られ、しかも金属をさびさせないので溶接などに利用される。

［守永健一］

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