What product is typically stored in a "Pressure Cargo Tank" classified as MC 331?

A "Pressure Cargo Tank" classified as MC 331 is specifically designed for transporting liquefied gases that can exist under pressure. This classification is often utilized for products such as ammonia, propane, and butane, which are commonly processed and transported in a liquid state under pressure.

Ammonia, typically stored for agricultural and refrigeration uses, is transported under pressure to maintain its liquid form. Similarly, propane and butane, both widely used as fuels in heating and cooking, are also kept under pressure to facilitate transport and prevent them from vaporizing.

The engineering design of MC 331 tanks ensures they can handle the high pressures that these gases maintain in their liquid state, making them particularly suitable for such products. This capability to safely transport these specific gases distinguishes MC 331 from other types of tanks that may store gases with different pressures or states.

In contrast, other options provide examples of substances that might be transported in other types of tanks, but they do not match the characteristics suitable for MC 331. For instance, Liquid Nitrogen is typically stored in cryogenic tanks, Liquid Oxygen often requires specialized cryogenic capabilities, and Freon and Ethylene would relate to different tank standards.