Final answer:
Acetylene cylinders should indeed be stored on their sides to prevent acetone leakage and ensure safety. The cylinders are designed with a safety factor and can contain gas at high pressures, but excessive heating can increase the pressure to unsafe levels.
Step-by-step explanation:
The statement that acetylene cylinders should be stored on their sides is true. Gas cylinders, such as those containing acetylene, are stored at high pressures, typically around 200 atmospheres. Acetylene cylinders contain a porous filler saturated with acetone, in which the acetylene is dissolved. Storing them upright can lead to the acetone being at the top, away from the gas outlet. When laid on their sides, the probability of acetone leakage into the gas line is reduced. Moreover, if a fire occurs and heat is applied to the tank, the pressure inside the cylinder will increase. The safety factor indicates that the cylinder might not fail until it reaches a pressure of about 400 atmospheres. However, heating can cause pressure to increase beyond this point, potentially leading to cylinder failure. Exact calculations to determine "how hot" the gas can get before reaching this failure point would require specific thermal properties of the gas and the cylinder material, as well as the initial temperature and pressure conditions to apply the gas laws and safety standards.