The implementation of chemical syntheses in a batch or semi-batch reactor is generally limited by the removal or the supply of heat. A way to enhance thermal performances is to develop multifunctional devices like heat exchanger/reactors. In this work, a novel heat exchanger/reactor is characterized in terms of residence time, pressure drops, and thermal behavior in order to estimate its capacities to perform an exothermic reaction: the oxidation of sodium thiosulfate by hydrogen peroxide. Experimental results highlight the performances of the heat exchanger/reactor in terms of intensification, which allows the implementation of the oxidation reaction at extreme operating conditions. These conditions are finally compared to the ones of a classical batch reactor.