I am designing an experiment that involves immersing pieces of pipe lining in a mixture of tert-butyl mercaptan (2 %) and white mineral oil (98 %) at 230 °C (the standard temperature for the test). If I was using pure tert-butyl mercaptan I would be concerned with it exploding, due to its auto ignition temperature being 250 °C. However, if the white mineral oil contains only 2 % tert-butyl mercaptan would the risk of autoignition be present at 230 °C?
I figure Mineral oil has vapour pressure of less than 1mm Hg. Tert butyl mercaptan has vapour pressure of 303 mm Hg. For the tert butyl mercaptan (2%) in mineral oil (98%) mixture I calculated that the partial pressure for tert butyl mercaptan would be 6.06 mm Hg and for mineral it would be 0.098 mm Hg. Therefore, the composition of gas above the surface of the mixture would be tert butyl mercaptan 98% and mineral oil 2%. If this is the case then the auto ignition temperature of pure tert butyl mercaptan of 250 °C would apply to the resultant gas and it would not be safe operate at 230 °C. Is this right?