When butane evaporates whats left?

Answer 1

Butane is a gas at atmospheric pressure and room temperature. In the fuel tanks of cigarette lighters, butane welding torches, and most other butane powered heating devices, butane has been compressed to the point that it remains liquid at room temperature. When the trigger of these devices is depressed, a valve opens, allowing butane to escape from the tank, and in doing so, it's pressure drops to atmospheric pressure, and the liquid butane escaping the tank rapidly boils and becomes a gas, which is ignited by an ignition source. Strictly speaking, if the tank contained pure butane, when all the butane has evaporated, all that would be left in the tank is butane gas at atmospheric pressure. If you sprayed liquid butane on your table, and it were completely pure, the liquid would evaporate, leaving nothing behind. In reality, butane fuel is not completely pure, and may contain small amounts of all sorts of contaminants, some of which can be left behind after the butane evaporates. Some of these contaminants like methane, ethane, and propane likely would evaporate away with the butane, but other contaminants, like trace amounts of other petroleum distillates will likely remain after the butane evaporates.