TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method further comprises: including a catalyst in the brine phase; selecting the soluble inorganic compound to protect the catalyst from poisoning; adding a compound to the brine to protect the catalyst from poisoning; collecting and disposing of the product effluence resulting from the reaction; injecting a fluid into the feed material during the introducing step, where the injected fluid has a temperature of greater than 374 degrees C, and is water or brine; removing residual solids and excess dissolved materials from the brine phase; and augmenting the brine phase with an oxidant. The method comprises providing a water mixture having a density of greater than 500 kg/m at a temperature of greater than 374 degrees C and introducing the feed material into the water mixture for reaction with it to produce the effluence. Preferred Components: The soluble inorganic compound is selected to prevent deposition of low solubility compounds. The catalyst is an alkaline compound comprising potassium carbonate or sodium hydroxide, where the effluence is a gas. The catalyst is a precious metal. The inorganic compound is a group comprising salts, oxide compounds or hydroxide compounds. The brine phase comprises water, at least one soluble inorganic compound and a catalyst.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The means for introducing is a downcomer pipe connecting the source of feed material in fluid communication with the chamber of the reactor vessel. The brine phase and a gaseous effluence coexist in the chamber with a liquid/vapor interface between them, where the downcomer pipe extends through the gaseous effluence and past the inter face into the brine phase, and the exit pipe is in fluid communication with only the gaseous effluence. The apparatus further comprises an injection pipe connected to the downcomer pipe for injecting a fluid into the feed material, where the fluid has a temperature of greater than 374 degrees C to rapidly preheat the feed material, and is water or brine; an injection pipe in fluid communication with the chamber of the reactor vessel for use in injecting the fluid into the brine phase for control of the brine phase; an oxidant pipe in fluid communication with the chamber of the reactor vessel for use in adding an oxidant to the brine phase; and a drain pipe for removing residual solids and excess dissolved materials from the brine phase. EXAMPLE - No suitable example given.