The last theory was not considered by the inquiry since it was formulated by scientists who continued to work on it after its closure. The rupture of the 20 inch pipe could be due to a sudden rise of pressure because of the water presents in reactor 4. An azeotrope could have formed between the water and the cyclohexane. Normally there is no water in the reactors but on the day of the accident, the stirrer (reactor 4) had a mechanical problem and was stopped: water may have been present. Cyclohexane and water are normally immiscible. The stirrers normally prevent the water from having a low solubility in the cyclohexane but, that day, two phases may have occurred with an unstable interfacial layer, the azeotrope. At start-up, the temperature increased, the boiling point of the azeotrope was reached and this may have led to a sudden pressure rise and the cyclohexane ejection. The bypass failed under the high pressure in the reactor.