Portable refrigerator

A thermostat system for controlling the temperature of a refrigerator chamber cooled by vapor escaping from an opening in a container of pressurized liquid positioned in said chamber, said thermostat system comprising:

• a. a thermally expandable and contractible support frame fixed relative to the base of said container with a movable end extending to the region of the top of said container;
• b. said support being in thermal communication with said container so said movable end moves in response to the temperature of said container;
• c. means positioned by said movable end for opening and closing said vapor opening;
• and
• d. said positioned means being arranged for opening said vapor opening when said chamber warms said container and said frame to an upper threshold temperature and for closing said vapor opening after escape of vapor from said container lowers the temperature of said container and said frame to a lower threshold temperature substantially below the temperature of said chamber.