I recently got hold of an old blowlamp that had not been touched for more than 30 years. The fuel tank of the blowlamp is made of brass. I poured the old kerosene from the blowlamp into a clean polyethene flask, the kerosene was clear and quite green in color. The flask got about half full.
The next day the kerosene had turned colorless and there was a brown precipitate. The flask was not shaken or subjected to strong light.
What happened here? Something that had been stable for years suddenly reacting. If it is a reaction with oxygen, does oxygen diffuse that easily through kerosene?
Was the green substance an inorganic copper salt dissolved in the kerosene or was it some kind of organic "copper kerosenate"?