Abstract: An apparatus for producing an air and liquid vapor mixture for connection into a fuel inlet stream of an internal combustion engine comprising a glass container having an open top through which liquid to be vaporized can be supplied to the container and a cap removably covering the open top of the container and providing a vacuum tight seal therefor, the cap having a rigid tube carried thereby, one end of which constitutes an exterior air inlet and the other end of which extends to an outlet position adjacent the bottom of the container and has a length of flexible tubing connected therewith which extends in a loop disposed along the container bottom and terminates in an end opening of a size less than the size of the air inlet of the rigid tube.