Free sulfur in petroleum products, especially gasoline, cannot be tolerated because of the serious corrosion problems that might follow. The specifications for gasoline call for a noncorrosive product, which necessitates the complete removal of any free sulfur in the fuel. At times removal may be difficult to accomplish, but the refiner usually is able to control operations to avoid the presence of free sulfur in motor fuel. Natural gasoline extracted from sour gas may contain some free sulfur, usually due to oxidation of some of the hydrogen sulfide. This sulfur may be difficult to remove unless the gasoline can be used for blending with refinery gasoline and then treated with doctor solution.