NOVELTY - The gas-generating apparatus comprises a reaction chamber (18) containing a solid fuel precursor (24), a reservoir (44) containing a liquid fuel precursor (22), a fluid path for introducing the liquid fuel precursor into the chamber, and a unit for introducing the liquid fuel precursor through the fluid path at a movable point. A portion of the liquid fuel precursor is introduced at locations in the solid fuel precursor into the chamber to react to produce a gas in response to a pressure within the chamber, where the portion is less than the entire liquid fuel precursor.    USE - The apparatus such as fuel cell cartridges is useful for generating gas such as hydrogen, which is useful as a fuel.    ADVANTAGE - The apparatus is capable of efficiently generating gas with improved performance, regulates the flow of liquid reactant into the reaction chamber, minimizes the migration of gas into the reservoir, and minimizes or avoids the need for lengthy recharges required by rechargeable batteries.    DETAILED DESCRIPTION - The gas-generating apparatus comprises a reaction chamber (18) containing a solid fuel precursor (24), a reservoir (44) containing a liquid fuel precursor (22), a fluid path for introducing the liquid fuel precursor into the chamber, and a unit for introducing the liquid fuel precursor through the fluid path at a movable point. A portion of the liquid fuel precursor is introduced at locations in the solid fuel precursor into the chamber to react to produce a gas in response to a pressure within the chamber, where the portion is less than the entire liquid fuel precursor. The reservoir comprises a flexible liner that is compressed to introduce the portion of the liquid fuel precursor into the reaction chamber. The movable point of introduction comprises a nozzle attached to the flexible liner. A first spring is a constant-force spring, acts on the flexible liner, and is arranged for compressing the flexible liner. The pressure in the reaction chamber acts on a pressure-sensitive member supported by a second spring. The pressure causes the pressure-sensitive member to act on the first spring to pause the compression of the flexible liner when the pressure in the reaction chamber exceeds a threshold level. The flexible liner comprises a corrugated liner. The solid fuel precursor is separated into smaller portions. The fluid path is disposed on a slidable piston separating the reaction chamber from the reservoir, and comprises a fluid transfer tube connected to the slidable piston. A sprag is connected to the slidable piston to limit the movement of the piston to a direction toward the reservoir. The reservoir is pressurized by a pressurized gas that is contained within an elastic bladder positioned inside the reservoir. The slidable piston is moved to introduce liquid fuel precursor to the reaction chamber when the pressure in the reaction chamber exceeds the pressure in the reservoir, and is moved to introduce liquid fuel precursor to the reaction chamber when the pressure in the reaction chamber exceeds the pressure in the reservoir and/or a pressure drop along the fluid transfer tube.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a gas-generating apparatus.    Reaction chamber (18)    Liquid fuel component (22)    Solid fuel component (24)    Spring (30)    Liquid impermeable membrane (32)    Reservoir. (44)