Abstract: A system for generating power in a variable volume engine using a liquid solvent and a soluble gas. Power is generated by decreasing the pressure within one or more variable volume chambers through the solution of ammonia in water when each chamber is at or near a maximum volume. The resulting differential between the atmospheric pressure and the reduced pressure within the chamber is used to generate mechanical power. The combing of the water and ammonia gas may take place within a conventional cylinder at a point in time when the associated piston is approximately bottom dead center. In a second embodiment, the ammonia and water is mixed in a tank at a remote location from the piston and cylinder. The cylinder is operatively connected with the tank such that the vacuum developed in the tank may be employed within the cylinder for the production of power.