A liquid dispensing device (2) and a method of dispensing liquid are disclosed. The device (2) includes a hollow gas and liquid tight casing (4), a flexible gas and liquid tight membrane (18, 130) having at least one convolution (132) and disposed across the casing interior and dividing the interior into a propellant chamber (36) and a liquid chamber (24), an outlet port (28) from the liquid chamber (24), two mutually reactive chemicals (38, 40) in the propellant chamber (36) but reactive upon contact to form a propellant gas. Upon generation of the gas, the gas expands against the membrane (18, 130), pressurizing the liquid chamber (24) to expel the contained liquid through the outlet port (28). A pressure relief valve (45), suitable for use with the device, allows gas to escape from the device when the gas pressure exceeds a predetermined level.