Even at low concentrations of the acids in the reaction solutions (1 wt.%), hydrolysis of MgH2 is very fast (see Figure ). The maximum H2 release rate is achieved after ~1 minute from the start followed by its decrease. In 3-5 minutes after the start, the H2 release rate drops below sensitivity threshold of the used flowmeters. The temperature increase results in the increase of the amount of hydrogen generated during this period, as well as in the increase of the maximum reaction rate which achieves 1.5-1.7 Nl/(min g) at T=50-70˚C. In the more concentrated solutions (≥2 wt.%), the measured time dependencies of H2 generation rate become very similar to the ones observed for the 1 wt.% solutions at T=50-75˚C exhibiting almost the same maximum reaction rates independently on the temperature. It can be explained by the heating of the reaction solution at the beginning of very fast and highly exothermic hydrolysis Reaction 2 3 thus introducing its uncontrollable acceleration.