What determines the amount of gas remaining in a liquid gas cylinder?

The amount of gas remaining in a liquid gas cylinder is primarily determined by the pressure within the cylinder. In a liquid gas cylinder, gas exists in two phases: liquid and vapor. As gas is used, the liquid phase transforms into vapor, and the pressure readings will reflect the changes in the gas state.

The pressure indicates how much gas is left; when the cylinder is full, the pressure will be at a certain level specific to the gas. As gas is drawn from the cylinder, the pressure will drop in a predictable manner until the liquid runs out, at which point only vapor remains, and the pressure will stabilize at a lower level.

While the weight of the cylinder could provide insight into how much gas is left, it is not a direct measurement of the amount of gas remaining. A cylinder could be weighed, but without knowing the weight of the cylinder when full, the weight alone cannot accurately determine how much gas is left.

Temperature can affect the pressure readings and the behavior of the gas, particularly in terms of its expansion or contraction; however, it is the pressure that gives the direct indication of the amount of gas. The color of the cylinder does not provide any information regarding the gas quantity and is primarily for identification and safety purposes.