Ni added magnesium hydrides have been thoroughly examined as hydrogen transporting media. They have great advantages on hydrogen content and cost. A serious disadvantage is their low packing density. This means that the container is inevitably bulky and heavy. One of the possibilities to cancel this disadvantage is to let this transportation system work as a hydrogen purification system simultaneously. To study the feasibility of these systems, the effects of impurity gas in hydrogen gas and adsorbed on the surface of powder particles on the reaction have been examined experimentally.