NOVELTY - The device for generating gas by contacting a liquid reagent and a solid element, comprises a liquid reagent reservoir (6), a reaction chamber (8) to contain the solid element, an outlet (26) for collecting the gas generated in the reaction chamber, and a unit for injecting the liquid reagent on the solid element. The reservoir and the reaction chamber are separated and sealed by a movable wall (4) such as a piston. The injection unit is integrated in movement of the movable wall and the solid element, and comprises a tube connecting the reservoir and the reaction chamber.    USE - The device is useful for generating hydrogen gas by contacting a liquid reagent and a solid element, and in an electric supply comprising a fuel cell, where the electric supply is useful in a portable electric element (all claimed).    ADVANTAGE - The device is simple, compact and effective for generating the hydrogen gas by ensuring an optimized kinetic reaction between the liquid reagent and the solid element with less consumption of energy thus capable of generating electricity in an efficient manner.    DETAILED DESCRIPTION - The device for generating gas by contacting a liquid reagent and a solid element, comprises a liquid reagent reservoir (6), a reaction chamber (8) to contain the solid element, an outlet (26) for collecting the gas generated in the reaction chamber, and a unit for injecting the liquid reagent on the solid element. The reservoir and the reaction chamber are separated and sealed by a movable wall (4) such as a piston. The injection unit is integrated in movement of the movable wall and the solid element, and comprises a tube connecting the reservoir and the reaction chamber. A movement of the piston in a decreasing volume direction of the reservoir causes a flow of the liquid reagent towards the reaction chamber. The reservoir is bounded by a flexible bladder that is to be deformed. The wall is connected to a screw mechanism comprising a rotatable shaft equipped with a thread cooperating with an internal thread that is fixed in an inner wall of the injection tube. The liquid reagent passes between the tube and the shaft, and includes a stabilizing agent such as soda. A toothed wheel is present at an end of the shaft and rotated manually or with an electric motor. A check valve is present between the reservoir and the reaction chamber. A ratchet type unit is arranged to prevent a movement of the movable wall in a volume increasing direction of the reservoir. The flexible bladder is formed by a membrane forming a part of the reservoir wall, and by a gas bubble contained in the liquid. Stress is exerted on the wall towards the reservoir causing an increase in pressure of the liquid reagent contained in the reservoir. The liquid reagent and/or the solid element comprises a catalyst for initiating the reaction. The solid element comprises a porous substrate on which the catalyst is deposited, and is associated with a porous and inert component opposite to the reaction. An INDEPENDENT CLAIM is included for an electric supply.    DESCRIPTION OF DRAWING(S) - The figure shows a longitudinal cross-sectional view of hydrogen gas generating device.    Casing (2)    Movable wall (4)    Reagent reservoir (6)    Reaction chamber (8)    Outlet. (26)