The liquefaction or liquefaction is the process of transforming matter from a gaseous state directly to a liquid state, by increasing the pressure of the gas (isothermal compression) and decreasing its temperature (adiabatic expansion). These conditions, in fact, distinguish liquefaction from condensation (transformation of a gas to a liquid by lowering the temperature of the gas).
This technique was discovered by the British scientist Michael Faraday in 1823, during his experiments with ammonia, and today it constitutes one of the most usual and indispensable procedures for handling gases for industrial and commercial consumption. For example: liquid oxygen, refrigerators, aerosols.
Examples of liquefaction
- liquefied chlorine. It is a very toxic compound is made from the compression of chlorine gases and is diluted in wastewater and swimming pools. Not to be confused with gaseous chlorine solutions.
- Liquid nitrogen. It is a liquefied gas that is used as a refrigerant and cryogenic agent. As it retains large amounts of heat, it is often used in dermatological therapies for removal or surgical burns, and for freezing semen and eggs.
- liquid oxygen. It is transported in a liquid state to hospitals, where it recovers its pressure and returns to a gaseous state. It serves to oxygenate the respiratory tract.
- helium liquefaction. Heike Kamerlingh Onnes in 1913 was the first to achieve the liquefaction of helium. This allowed the generation of liquid helium (-268.93 °C), the thermomechanical effect and other discoveries that provided valuable information on the noble gases.
- Liquefied propane and butane. They are gases of common commercial and industrial use. Due to their flammability and cheap cost, they are transported in tanks and bottles much more comfortably in liquid form, since they take up less space (approximately 600 times less volume) and are more manageable.
- ordinary lighters. The liquid content of common plastic lighters is made up of liquefied gases that, when the button is operated and the spark is ignited, return to their gaseous form and feed the flame. Therefore, heating a lighter is a bad idea: the liquid returns to its gaseous form and presses out, causing the plastic container to burst.
- refrigerators. Refrigerators and freezers generate cold from a circuit of liquefied gases inside the condenser, which extract heat and allow temperatures to be kept low.
- Liquefied petroleum gas. Dissolved in oil or natural gas, these are hydrocarbons that are very easy to liquefy, obtained by catalytic fractional distillation (cracking) and used as gaseous fuel.
- Aerosols and sprays. The content of many aerosols is suspended in a high-pressure gas, whose form in the container is liquid but, once the device is activated, it returns to ambient pressure and recovers its gaseous condition, spraying the targeted surface with paint or desired substance and releasing the rest of the gases into the environment.
- Carbon dioxide (COtwo) liquid. As a previous step to obtaining dry ice, or as part of other industrial processes that require it, COtwo abundant in the atmosphere can be liquefied by subjecting it to extreme pressure.
- ammonia liquefaction. As part of its use in making numerous cleaners or solvents, ammonia (NH3) can be liquefied. This is often used in weather balloons to add ballast, which can then easily be returned to a gaseous state and lift the ship.
- air liquefaction. It is the method of obtaining pure elements for industrial use: air is taken from the atmosphere and liquefied at high pressure, to later separate its constituent elements and store them separately, such as nitrogen, oxygen and argon.
- Liquefied noble gases. They are widely used in the medical field of infrared spectroscopy. They are used as solvents since they are transparent to this type of radiation and do not obscure the spectrum of the particles or substances dissolved in them.
- superconductors. In large scientific or computerized facilities whose equipment generates a lot of heat, liquefied gases at very low temperatures (such as hydrogen and helium) are used to prevent overheating of the delicate specialized machinery.
- liquefied argon. It is used scientifically in the study of dark matter, through huge detectors that contain certain amounts of argon in gas and in liquid, to emit light every time a particle of dark matter collides with an atom of this element.