Liquid air is air that has been cooled to cryogenic temperatures, causing it to condense into a pale blue mobile liquid. It is stored in specialized insulated containers, such as vacuum flasks, to maintain its low temperature and prevent it from returning to its gaseous state.

How is liquid air stored to maintain its low temperature?

Liquid air is stored in specialized containers, such as vacuum flasks, designed to insulate it from ambient room temperature and minimize heat transfer. This insulation helps maintain its extremely low temperature.

What are the primary industrial uses of liquid air?

Liquid air serves as an industrial source for nitrogen, oxygen, and argon through air separation processes. It is also used for condensing other substances into liquid or solid form due to its rapid heat absorption capabilities.

What is the approximate density of liquid air?

The approximate density of liquid air is 870 kilograms per cubic meter (kg/m³), which is equivalent to 870 grams per liter (g/L) or 0.87 grams per cubic centimeter (g/cm³). This density can vary slightly based on the specific composition of the air sample, such as humidity or carbon dioxide concentration.

Why might the density of a specific sample of liquid air vary?

The density of a specific sample of liquid air can vary depending on its exact composition. Factors like humidity content and the concentration of carbon dioxide can influence the overall density of the liquid.

Under typical conditions, does carbon dioxide exist as a liquid in liquid air?

At pressures below 5.1 atmospheres (520 kPa), carbon dioxide does not typically exist as a liquid in liquid air. Instead, it solidifies directly from the gas phase without becoming liquid, meaning it is generally absent from liquid air under normal conditions.

What is the boiling point of liquid air?

The boiling point of liquid air is approximately -194.35 degrees Celsius (-317.83 degrees Fahrenheit or 78.80 Kelvin). This temperature falls between the boiling points of its primary components, liquid nitrogen and liquid oxygen.

What challenges exist in maintaining a stable temperature for liquid air?

Maintaining a stable temperature for liquid air can be challenging because its components boil off at different rates. Nitrogen, being more volatile, tends to boil off first, leaving the remaining liquid oxygen-rich and altering its boiling point. This process can also occur if liquid air condenses oxygen directly from the surrounding atmosphere.

At what temperature does liquid air begin to freeze?

Liquid air begins to freeze at approximately 60 Kelvin (-213.2 degrees Celsius or -351.7 degrees Fahrenheit). At this temperature, a nitrogen-rich solid precipitates, although it may contain a significant amount of dissolved oxygen.

What is the eutectic freezing point mentioned in relation to liquid air components?

The eutectic point for liquid air components freezes at 50 Kelvin, provided the oxygen is not already accommodated within a solid solution. The eutectic point represents the lowest possible freezing point for a mixture of substances.

Historically, why were air's constituents considered permanent gases?

The constituents of air were historically referred to as permanent gases because they could not be liquefied simply by increasing pressure at room temperature. This meant that traditional methods of liquefaction, like compression alone, were insufficient.

How does the process of liquefying air overcome the 'permanent gas' challenge?

Liquefying air involves a process that raises the gas temperature through compression, then removes this heat via cooling to ambient temperature. Subsequently, the gas expands, causing a significant temperature drop. By using counter-flow heat exchange, the incoming pressurized air is further cooled by the already expanded, colder air, eventually leading to the formation of liquid air droplets.

Who were the first scientists to liquefy the main constituents of air?

The primary constituents of air were first liquefied in 1883 by Polish scientists Karol Olszewski and Zygmunt Wrblewski. Their work marked a significant milestone in understanding and manipulating gases at low temperatures.

Are devices for producing liquid air readily available commercially?

According to the source, devices for the production of liquid air are not commercially available and are not easily fabricated. This suggests specialized equipment and expertise are required for their construction and operation.

What is the most common industrial process used to prepare liquid air?

The most common industrial method for preparing liquid air is the two-column Hampson–Linde cycle, which utilizes the Joule–Thomson effect. This process involves high-pressure and low-pressure columns to achieve the separation of air's components.

Describe the role of the Joule–Thomson effect in air liquefaction.

The Joule–Thomson effect is a key principle used in air liquefaction processes like the Hampson–Linde cycle. It describes the temperature change of a real gas or liquid when it is forced through a valve or porous plug while keeping other variables constant. In this context, expansion of compressed air causes a drop in temperature, facilitating liquefaction.

How does the Hampson–Linde cycle separate air components?

In the Hampson–Linde cycle, air is fed at high pressure into a lower column where it separates into pure nitrogen and oxygen-rich liquid. This oxygen-rich liquid, along with some nitrogen, is then fed into an upper column operating at lower pressure. Final separation into pure nitrogen and oxygen occurs in this upper column, and raw argon can be extracted from the middle.

What pressures are typically involved in the Hampson–Linde cycle for air separation?

The Hampson–Linde cycle operates with air fed at high pressure, typically exceeding 75 atmospheres (7,600 kPa or 1,100 psi), into the lower column. The upper column operates at a lower pressure, generally less than 25 atmospheres (2,500 kPa or 370 psi).

Besides the Hampson–Linde cycle, what other process can liquefy air?

Air can also be liquefied using Claude's process. This method combines the cooling effects of the Joule–Thomson effect with isentropic expansion and regenerative cooling techniques.

How is liquid air typically utilized after its production?

After production, liquid air is usually fractionated into its constituent gases, nitrogen, oxygen, and argon. These gases can be used in either liquid or gaseous form for various industrial and medical applications.

What are the primary applications for oxygen derived from liquid air?

Oxygen separated from liquid air is particularly useful for fuel gas welding and cutting processes. It is also employed for medical purposes, where supplemental oxygen is required.

What is the role of argon obtained from liquid air?

Argon derived from liquid air is valuable as a shielding gas in gas tungsten arc welding, also known as TIG welding. It helps to prevent the molten weld pool from reacting with atmospheric gases like oxygen.

Why is liquid nitrogen often preferred over liquid air for some low-temperature applications?

Liquid nitrogen is often preferred for low-temperature applications because it is nonreactive at normal temperatures, unlike oxygen which can pose a fire hazard. Liquid nitrogen boils at 77 K (-196 °C or -321 °F), providing a stable cryogenic coolant.

What historical attempt was made to use liquid air for transportation?

Between 1899 and 1902, an American/English company produced and demonstrated an automobile named Liquid Air. They claimed this vehicle could travel one hundred miles on a single charge of liquid air.

What recent development suggests liquid air could be used for energy storage?

In October 2012, the Institution of Mechanical Engineers highlighted the potential of liquid air for energy storage. This was linked to technology developed by garage inventor Peter Dearman in Hertfordshire, England, intended for powering vehicles.

What are some related topics mentioned in the 'See also' section of the article?

The 'See also' section lists related topics such as liquid nitrogen, liquid oxygen, cryogenic energy storage, industrial gas, liquefaction of gases, and liquid nitrogen vehicles. These topics are connected through the principles of cryogenics and gas separation.

What is the significance of the 'More citations needed' template in the article?

The 'More citations needed' template indicates that the article requires additional references to reliable sources to verify its information. Readers are encouraged to help improve the article by adding citations, and unsourced material may be subject to challenge or removal.

What is the primary purpose of storing liquid air in vacuum flasks?

The primary purpose of storing liquid air in vacuum flasks is to provide excellent thermal insulation. These specialized containers minimize heat transfer from the warmer surroundings, helping to keep the liquid air at its cryogenic temperature and prevent it from rapidly boiling back into a gas.

How does the composition of dry air influence the density calculation of liquid air?

Since dry gaseous air is composed of approximately 78% nitrogen, 21% oxygen, and 1% argon, the density of liquid air is calculated based on the percentages of these components and their individual liquid densities. This means the overall density is a weighted average influenced by the proportions of nitrogen and oxygen.

What is the role of counter-flow heat exchange in liquefying air?

Counter-flow heat exchange is crucial in the process of liquefying air. It allows the cold, expanded air exiting the system to cool the incoming pressurized air, thereby increasing the efficiency of the cooling process and enabling the air to reach temperatures low enough for liquefaction.

What is the difference between the lower and upper columns in the Hampson–Linde cycle?

The lower column in the Hampson–Linde cycle operates at high pressure and performs an initial separation of air into nitrogen and oxygen-rich liquid. The upper column operates at lower pressure and refines this separation, yielding pure nitrogen and oxygen.

What is meant by air separation or air rectification in the context of liquid air?

Air separation, also referred to as air rectification, is the industrial process used to separate liquid air into its primary components, such as nitrogen, oxygen, and argon. This process is essential for obtaining these gases in pure forms for various applications.

What is the significance of liquid air's pale blue color?

The text describes liquid air as a pale blue mobile liquid. This color is characteristic of liquefied oxygen, which is slightly blue, and indicates the presence of oxygen in the liquid mixture.

How does the presence of oxygen affect the stability of liquid air?

The presence of oxygen can affect the stability of liquid air because oxygen-rich liquid air has a different boiling point than pure nitrogen or pure air. As nitrogen boils off, the remaining liquid becomes richer in oxygen, potentially leading to changes in temperature and increased reactivity.

What is the role of reflux in the upper column of the Hampson–Linde cycle?

In the Hampson–Linde cycle's upper column, reflux involves feeding the oxygen-rich liquid and some nitrogen back into the column. This process aids in the final separation of pure nitrogen and oxygen by providing a liquid flow that interacts with the rising vapor.

What is the purpose of purifying argon extracted from the Hampson–Linde cycle?

A raw argon product can be removed from the middle of the upper column in the Hampson–Linde cycle. This raw argon then requires further purification to be used effectively in applications like shielding gas for welding.

How does isentropic expansion contribute to liquefying air in Claude's process?

In Claude's process, isentropic expansion involves expanding a gas in a way that minimizes entropy changes, typically by doing work. This expansion process significantly lowers the temperature of the air, contributing to its liquefaction alongside the Joule–Thomson effect and regenerative cooling.

What does the term cryogenic temperatures refer to in the context of liquid air?

Cryogenic temperatures are extremely low temperatures, typically below -150 degrees Celsius (-238 degrees Fahrenheit or 123 Kelvin). Liquid air exists at these very low temperatures, which are necessary for it to remain in its liquid state.

What is the significance of liquid air's ability to absorb heat rapidly?

Liquid air's capacity to absorb heat rapidly means it can be used effectively as a cooling agent. This property allows it to condense other substances into liquids or even solids by drawing heat away from them.

What is the difference between liquid nitrogen and liquid oxygen in terms of their properties relevant to liquid air?

Liquid nitrogen and liquid oxygen are the primary components of liquid air. Liquid nitrogen has a lower boiling point (-196 °C) than liquid oxygen (-183 °C), meaning nitrogen evaporates first when liquid air warms up. Liquid oxygen is slightly blue, contributing to the color of liquid air.

What does the term mobile liquid mean when describing liquid air?

Describing liquid air as a mobile liquid indicates that it flows easily, similar to water or other common liquids. This contrasts with solids or highly viscous substances, highlighting its fluid nature at cryogenic temperatures.

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Defining Liquid Air

A Condensed Atmosphere

Liquid air represents the atmospheric gases, primarily nitrogen and oxygen, that have been cooled to extremely low temperatures, transitioning them into a condensed liquid state. This cryogenic fluid is characterized by its pale blue hue and high mobility. Its storage necessitates specialized, highly insulated containers, such as vacuum flasks, to mitigate heat transfer from the ambient environment and prevent rapid reversion to its gaseous phase.

Cryogenic Temperatures

Achieving the liquid state requires cooling air to cryogenic temperatures, typically below its boiling point of approximately -194.35 °C (78.80 K). At these temperatures, the kinetic energy of the gas molecules is significantly reduced, allowing intermolecular forces to dominate and cause condensation. This property makes liquid air a potent medium for cooling and condensing other substances.

Source of Industrial Gases

Industrially, liquid air serves as a crucial source for obtaining its constituent gases, namely nitrogen, oxygen, and argon, in high purity. This separation is achieved through a sophisticated process known as air separation or air rectification. The resulting gases are vital components in numerous industrial, medical, and scientific applications.

Physical Properties

Density and Composition

The density of liquid air is approximately 870 kg/m³ (0.87 g/cm³). This value is contingent upon the specific composition of the air sample, which can vary based on factors like humidity and carbon dioxide concentration. Standard dry air comprises roughly 78% nitrogen, 21% oxygen, and 1% argon. The density of the liquid form is calculated based on the weighted average density of these components in their liquid states. Notably, trace amounts of carbon dioxide solidify without liquefying under standard atmospheric pressure, thus not typically being present in liquid air.

Boiling Point and Phase Transitions

Liquid air possesses a boiling point of -194.35 °C (78.80 K). This temperature lies between the boiling points of pure liquid nitrogen (-196 °C) and liquid oxygen (-183 °C). A significant characteristic is its tendency to boil unevenly; nitrogen, being more volatile, evaporates first. This process enriches the remaining liquid with oxygen, altering its boiling point and potentially leading to hazardous oxygen-rich mixtures. In certain conditions, liquid air can also cause atmospheric oxygen to condense, further increasing oxygen concentration.

Freezing Point

Liquid air begins to solidify at approximately 60 K (-213.2 °C). At this temperature, a nitrogen-rich solid phase precipitates, often containing a significant amount of dissolved oxygen. If the oxygen cannot form a solid solution, the mixture reaches its eutectic point and freezes completely at around 50 K (-223.2 °C).

Production Methods

Principle of Liquefaction

Historically termed "permanent gases," atmospheric constituents like nitrogen and oxygen could not be liquefied by simple compression at room temperature. Liquefaction requires a multi-stage process involving compression, heat removal, and expansion. Compression increases gas temperature; this heat must be efficiently removed. Subsequent expansion, particularly through processes leveraging the Joule-Thomson effect or isentropic expansion, causes a significant temperature drop. Counter-flow heat exchange, where incoming compressed gas is cooled by the outgoing expanded gas, is critical for achieving the necessary low temperatures for condensation.

Historical Milestone

The initial liquefaction of air's main components was achieved in 1883 by Polish scientists Karol Olszewski and Zygmunt Florenty Wróblewski. Their pioneering work marked a significant advancement in cryogenics, enabling further research and industrial applications.

The predominant industrial method for producing liquid air is the Hampson–Linde cycle. This process utilizes the Joule-Thomson effect, typically involving a two-stage system. High-pressure air (often exceeding 75 atm) is fed into a lower-pressure column where initial separation occurs, yielding pure nitrogen and oxygen-rich liquid. This liquid, along with some nitrogen, is then processed in an upper, low-pressure column (below 25 atm) to achieve final separation into high-purity nitrogen and oxygen. Argon can be extracted as a byproduct from the middle section of the upper column.

Claude's Process

An alternative method is Claude's process, which enhances efficiency by combining the Joule-Thomson effect with isentropic expansion and regenerative cooling. This approach involves using an expansion engine to perform work, thereby achieving greater cooling than simple throttling, and employing heat exchangers to pre-cool the incoming air stream, leading to more effective liquefaction.

Industrial Significance

Welding and Cutting

The high-purity oxygen derived from liquid air is indispensable for oxy-fuel welding and cutting processes. The intense heat generated by burning fuel gases in the presence of pure oxygen enables efficient metal fabrication and demolition.

Medical Applications

Medical-grade oxygen, separated from liquid air, is critical for respiratory therapy, anesthesia, and life support systems in healthcare settings worldwide.

Shielding Gas

Argon, another key component extracted via air separation, is widely used as a shielding gas in welding processes like gas tungsten arc welding (GTAW). It protects the molten weld pool from atmospheric contamination, ensuring weld integrity and quality.

Low-Temperature Applications

Liquid nitrogen, readily available from liquid air fractionation, is utilized in a vast array of low-temperature applications. Its inert nature at normal temperatures, unlike oxygen, makes it suitable for applications requiring rapid cooling, cryopreservation, and specialized industrial processes.

Transport and Storage

Specialized Containers

Due to its cryogenic nature, liquid air requires storage and transport in highly specialized containers. These are typically vacuum-insulated vessels, often referred to as vacuum flasks or dewars, designed to minimize heat ingress from the surroundings. This insulation is crucial for maintaining the liquid state and preventing rapid boil-off.

Energy Storage Potential

Liquid air has been explored as a medium for energy storage, particularly for renewable energy sources. Technologies, such as those developed by Peter Dearman, propose using the expansion of liquid air to drive turbines and generate electricity. This concept, often termed Cryogenic Energy Storage (CES), leverages the phase change from liquid to gas to store energy, potentially offering a solution for grid-scale storage of intermittent power sources like wind and solar.

Historical Vehicle Concepts

Early concepts for vehicles powered by liquid air emerged around the turn of the 20th century. Between 1899 and 1902, an Anglo-American company produced and demonstrated a car purported to run on liquid air, highlighting early interest in its potential as a motive force, though practical challenges ultimately limited widespread adoption.

Related Concepts

Core Principles

Liquid Nitrogen
Liquid Oxygen
Cryogenic Energy Storage
Liquefaction of Gases

Industrial Context

Industrial Gas
Air Separation

Historical Technology

Liquid Nitrogen Vehicle

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References

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The Chilling Depths of Liquid Air

💡 Dive in with Flashcard Learning! 💡

Defining Liquid Air ℹ️

💧 A Condensed Atmosphere

🌡️ Cryogenic Temperatures

🏭 Source of Industrial Gases

Physical Properties 🔬

⚖️ Density and Composition

♨️ Boiling Point and Phase Transitions

🥶 Freezing Point

Production Methods ⚙️

💡 Principle of Liquefaction

📜 Historical Milestone

Hampson–Linde Cycle

⚙️ Claude's Process

Industrial Significance 🏭

✂️ Welding and Cutting

🩺 Medical Applications

🛡️ Shielding Gas

❄️ Low-Temperature Applications

Transport and Storage 🚚

📦 Specialized Containers

🔋 Energy Storage Potential

🚗 Historical Vehicle Concepts

Related Concepts 🔗

⚗️ Core Principles

🏭 Industrial Context

🚗 Historical Technology

Teacher's Corner 🧑‍🏫

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📜 Important Notice

Dive in with Flashcard Learning!

Defining Liquid Air

A Condensed Atmosphere

Cryogenic Temperatures

Source of Industrial Gases

Physical Properties

Density and Composition

Boiling Point and Phase Transitions

Freezing Point

Production Methods

Principle of Liquefaction

Historical Milestone

Claude's Process

Industrial Significance

Welding and Cutting

Medical Applications

Shielding Gas

Low-Temperature Applications

Transport and Storage

Specialized Containers

Energy Storage Potential

Historical Vehicle Concepts

Related Concepts

Core Principles

Industrial Context

Historical Technology

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice