Liquid Oxygen: Properties and Applications
Liquid oxygen, also known as LOx, is the liquid form of molecular oxygen and finds wide-ranging applications in aerospace, submarines, and the gas industry. This article will delve into the physical properties of liquid oxygen and its significant applications across various fields.
Physical Properties
The unique physical properties of liquid oxygen make it invaluable in different domains. Here are the key properties of liquid oxygen:
1. Density and Temperature
At standard atmospheric pressure (101.325 kPa), liquid oxygen has a density of 1.141 g/cm³, slightly higher than that of liquid water. Liquid oxygen exhibits an extremely low freezing point at 50.5 K (equivalent to -222.65 degrees Celsius) and a boiling point of 90.188 K (equivalent to -182.96 degrees Celsius). This enables the existence of liquid oxygen under extremely low-temperature conditions, making it suitable for various applications.
2. Liquefaction Process
Industrial production of liquid oxygen typically involves a process called fractional distillation. This process entails compressing and cooling air to separate nitrogen and oxygen. Due to their different boiling points, nitrogen is separated first, leaving relatively pure liquid oxygen behind.
3. Appearance and Magnetism
Liquid oxygen has a pale cyan color and exhibits strong paramagnetism. It can be suspended between the poles of a powerful horseshoe magnet.
4. Inducing Material Brittleness and Strong Oxidizing Agent
Materials in contact with liquid oxygen become extremely brittle due to its low-temperature nature. Additionally, liquid oxygen is a potent oxidizing agent, causing organic materials to combust rapidly. Certain substances like coal briquettes, carbon black, etc., can unpredictably detonate when soaked in liquid oxygen and exposed to ignition sources like flames, sparks, or minor impacts. Petrochemicals, including asphalt, often display this behavior.
Applications
Liquid oxygen finds extensive applications, spanning several domains.
Here are some of its primary applications.
1. Medical Use
In the medical field, liquid oxygen is utilized for oxygen therapy to ensure patients receive an adequate oxygen supply. High-altitude aircraft also employ liquid oxygen to provide breathing oxygen to passengers and crew.
2. Industrial Manufacturing
The industrial manufacturing of liquid oxygen involves fractional distillation of liquid air. With an expansive ratio of 1:861, liquid oxygen finds widespread use in modern industrial production, including metallurgy, chemical engineering, and electronics manufacturing. In many industrial applications, people use ambient vaporizers to regain its gaseous state into typical application.
3. Oxidizer
Liquid oxygen is commonly used as an oxidizer, especially in rocket propulsion. It is combined with various fuels such as liquid hydrogen, kerosene, or methane to provide substantial thrust, launching spacecraft into orbit. It plays a crucial role in aerospace engineering.
Safety Considerations
Due to its low temperature and oxidizing properties, liquid oxygen poses certain risks. Liquid nitrogen has a lower boiling point than liquid oxygen, and vessels containing liquid nitrogen can condense oxygen from the air. Consequently, after most of the nitrogen has evaporated from such a vessel, the remaining liquid oxygen can react violently with organic materials, presenting an explosion hazard. Conversely, liquid nitrogen or liquid air can be enriched with oxygen by allowing them to stand in open air, as atmospheric oxygen dissolves in them, while nitrogen preferentially evaporates.
