Hydrogen in Metals III is the fifth book in the series Topics in Applied Physics that discusses properties of metal-hydrogen systems. It considers results of both basic and application-oriented research, focusing on fields where recent progress was significant or where previous comprehensive reviews do not exist. The topics of the new volume are: the theoretical and the experimental status of hydrogen diffusion; nuclear magnetic resonance; neutron scattering; material problems caused by the hydrogen; application of metal hydrides for hydrogen storage and purification, for chemical engines, for hydrogen sensors, and for batteries and fuel cells.