Abstract: A double valve for dispensing from or emptying a cylinder independently of internal cylinder pressure includes a first and second spring loaded toggle valve, an input port, an output port, a dip tube, and first and second monitoring ports to facilitate monitoring of pressure within and without the cylinder. A source of pressurized inert gas is connected to the input port, volatilizing the contents of the cylinder and expelling them through the output port. Communication between the input port and output port is controlled by the first and second spring loaded toggle valves.