Investigations have shown that a violent event (normally auto-ignition) occurs after a relatively short period of time when the two immiscible liquids Otto Fuel II and 82% aqueous hydroxylammonium perchlorate (HAP) come into contact at temperatures between 30degreesC and 50degreesC. Under quiescent conditions the time from initial contact to an event (time-to-event) depends on the relative volumes of the liquids as well as the temperature but there is no significant difference between the time-to-event recorded in an open container and that recorded in a sealed container at the same temperature. It is concluded that key reactions in the build up to an event are taking place in both the Otto Fuel II and in the HAP solution.