When environmental crews started cleaning up a closed government WWII laboratory

Question

When environmental crews started cleaning up a closed government WWII laboratory, they discovered thousands of unlabeled gas cylinders (25 L) and wondered how to identify them. They knew that the cylinders mostly contained oxygen, methane, and helium, but some contained xenon or uranium hexafluoride. The cylinders are rusty and old, so they don't want to open each cylinder and send thousands of samples to an analytical laboratory. However, after scrounging around they find a scale, a pressure gauge, a large vat of water, several dozen packs of bubble gum, a large pile of snow in the parking lot, some firewood and matches, and their old thermodynamics textbook. Using your extensive knowledge of thermodynamics, suggest 2 or 3 (non-lethal) ways to the crew for identifying the correct gas in each cylinder using just these items. Or suggest how you might also use the Maxwell relationships with these items for an extra 5 points! Clearly state your assumptions, and provide as much detail on the procedures as possible.

Explanation / Answer

FOLLOW THIS Compressed gases are stored in heavy-walled metal cylinders designed, produced and tested for use with compressed gases. Cylinders are made in a wide variety of sizes and shapes. They range from small lecture bottles, often used for demonstration purposes, to large cylinders over 3 metres long. Cylinders for transportation must meet Canadian Standards Association standard CAN/CSA-B339 "Cylinders, Spheres and Tubes for the Transportation of Dangerous Goods". This standard covers requirements for the manufacturing, inspection, testing, marking, requalification, reheat treatment, repair, and rebuilding of cylinders, spheres, and tubes (containers) for the transportation of dangerous goods. In addition, it includes the requirements for the qualification of new designs and registration requirements. You should also consult CAN/CSA-B340 "Selection and Use of Cylinders, Spheres, Tubes, and Other Containers for the Transportation of Dangerous Goods, Class 2". Cylinders that meet these criteria are often referred to as "TC approved" cylinders. Cylinders are permanently marked, typically on the shoulder or the top surface of its neck. Usually, cylinders must be retested or inspected every five or ten years. The date of each test must be stamped on the cylinder. Cylinder Valves and Connections Compressed gas cylinders must be connected only to regulators and equipment designed for the gas in the cylinder. Since connecting the wrong equipment can be dangerous, a number of different standard cylinder valve outlets are available for different classes of gas. For example, these standard connections prevent the valve connection for a flammable gas from fitting the connections for an incompatible gas, such as an oxidizing gas. Most compressed gas cylinders have valve caps or some other method of protecting the valve from damage during handling and transportation. A dust cap may be placed over the valve outlet itself to help keep it clean. What are cylinder safety devices? Most cylinders have one or more safety-relief devices. These devices can prevent rupture of the cylinder if internal pressure builds up to levels exceeding design limits. Pressure can become dangerously high if a cylinder is exposed to fire or heat, including high storage temperatures. There are three types of safety-relief devices. Each relieves excessive gas pressures in a different way: Safety- or Pressure-Relief Valves: These valves are usually a part of the cylinder. They are normally held closed by a spring. The force holding the valve closed is set according to the type of gas in the cylinder. The valve opens if the cylinder pressure exceeds the set safety limit. Gas is released until the cylinder pressure drops back to the safety limit. The valve then closes and retains the remaining gas in the cylinder. Rupture Discs (also known as frangible or bursting discs): These discs are usually made from metal. They burst or rupture at a certain pressure, releasing the gas in the cylinder. The bursting pressure is designed so that the disc ruptures before the cylinder test pressure is reached. These devices cannot be reclosed, so the entire contents of the cylinder are released. Fusible Plugs (also called fuse or melt plugs): Temperature, not pressure, activates fusible plugs. These safety devices are used where heat could initiate an explosive chemical reaction. A pressure-relief valve or rupture disc acts too slowly and too late to prevent rupture of the cylinder if an explosive reaction has already begun. The fusible plug releases the gas before the hazardous reaction can begin. Fusible plugs are made of metals that melt at low temperatures. For example, acetylene cylinders have a fusible plug which melts at about 100

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