NOVELTY - The apparatus comprises a reaction vessel, a piston and tension spring assembly, a supporting grid (46), an inlet (48) for adding reaction water, an outlet for releasing hydrogen, and an outlet for dislodging a waste solution of reaction. The reaction vessel comprises a first chamber for receiving reactant capsules (44) before an addition of reaction water to the vessel, and a second chamber (42) configured to accommodate the reaction water from the first chamber when a reaction between the reactant capsules and the reaction water is stopped.    USE - The apparatus is useful for producing high purity hydrogen from water such as tap water, reclaimed water, industrial grade water and sea water (claimed), where hydrogen is useful: for electric power generation via use of a polymer electrolyte membrane fuel cell, turbines, internal combustion engines or diesel engines; in high-power density portable and miniature power systems for electronics and uninterrupted power supply units; and for space and military applications including soldier power supply, unmanned aerial vehicles and air-independent propulsion for submarines.    ADVANTAGE - The compact apparatus is capable of efficiently and economically producing the hydrogen with high purity and without harmful contaminants such as carbon monoxide, hydrogen sulfide, ammonia and unsaturated and aromatic hydrocarbons.    DETAILED DESCRIPTION - The apparatus comprises a reaction vessel, a piston and tension spring assembly, a supporting grid (46), an inlet (48) for adding reaction water, an outlet for releasing hydrogen, and an outlet for dislodging a waste solution of reaction. The reaction vessel comprises a first chamber for receiving reactant capsules (44) before an addition of reaction water to the vessel, and a second chamber (42) configured to accommodate the reaction water from the first chamber when a reaction between the reactant capsules and the reaction water is stopped. The first and second chambers are divided by a partition, where a lower end of the partition is suspended above and distanced from a bottom of the reaction vessel for permitting fluid communication between the first and second chambers underneath the partition. The piston and tension spring assembly is coupled to a top portion of the second chamber to accommodate pressure that builds up from the reaction between the reactant capsules and the reaction water. The supporting grid is contained in the first chamber to support the reactant capsules, is located above and distanced from a bottom of the first chamber, and permits the reaction water. The inlet is disposed at a top portion of the first chamber of the vessel with a cap. The outlet for releasing hydrogen is disposed at the top portion of the first chamber, and includes a valve (50) to stop a flow of hydrogen and to move the reaction water to the second chamber. The outlet for dislodging a waste solution of the reaction is disposed at the bottom of the first chamber of the reaction vessel. Each reactant capsules have water dissolving polymeric jackets. One of the reactant capsules contains an alkali metal-based compound, transition metal and its compound, and a metallic ingredient including elements of groups IIA-IVA and VIII and their alloys.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of an apparatus for hydrogen production.    Second chamber (42)    Reactant capsules (44)    Supporting grid (46)    Inlet (48)    Valve. (50)