The cyclic hydriding and dehydriding property of LaNi₅ was examined with respect to pressure-composition-temperature(P-C-T) relation and hydrogen transfer using open and closed systems. Several important factors such as vacuum leak rate, hydrogen purity and temperature were found to be crucial for the cyclic property. This work points out the neccesity of the standardization of measurement and assessment methods for the cyclic property of hydrogen storage alloys.

A new method of hydrogen generation by magnesium pellets was proposed. Hydrogen was generated by putting magnesium pellets, composed of magnesium particles and some catalyst, into salt water. The rate of hydrogen generation was very fast and the quantitative amount of hydrogen was obtained in a short time period. This hydrogen evolution system was applied to in-situ reduction of organic compounds and inorganic spesies. Among them, ketones were quite easily reduced to alcoholes and the iron ion species were also reduced and almost perfectly removed out from the solution.

Hydrogen fueled engines have a strong advantage over environmental pollution in its exhaust gases except for NOx because of no carbon and

sulfer elements in the fuel. Experimental works to reduce the NO_x have been carried out applying the methods of EGR, cold hydrogen injection, fuel injection timing retardation and the combination of the methods has also been studied. As the results , it has been found that NO_x can be reduced to an enough low value in case of the operation of LH₂-pump high pressure hydrogen injection engines.