A novel type of gas-liquid contactor was researched and developed to enhance phase mixing. These high velocity impinging stream reactors are characterised by small reactor volumes supplied with nozzles, which are directed towards each other. The gas and liquid feed streams are jetted through the nozzles into the reactor volume, resulting in a highly turbulent mixture of the phases. Under these enhanced mixing conditions, mass transfer rates are increased dramatically. A mechanism for bubble formation and breakup in gas-liquid jet reactors. operated in the bubble mode, is proposed and a design philosophy of such reactors is also formulated.