Argon
[CAS# 7440-37-1]

Identification

• Classification: Inorganic chemical industry >> Industrial gases such as hydrogen, nitrogen and oxygen
• Name: Argon
• Molecular Formula: Ar
• Molecular Weight: 39.95
• CAS Registry Number: 7440-37-1
• EC Number: 231-147-0
• SMILES: [Ar]

Properties

• Density: 1.656 g/mL (Expl.)
• Melting point: -189.2 $degree$C (Expl.)
• Boiling point: -185.7$+/-$9.0 $degree$C 760 mmHg (Calc.)^*, -185.7 $degree$C (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS04 Warning
• Risk Statements: H280-H281
• Safety Statements: P282-P336+P317-P403-P410+P403

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Gases under pressure (compressed)	Press. Gas (Comp.)		H280
Gases under pressure (refrigerated liquid)	Press. Gas (Ref. Liq.)		H281
Gases under pressure (liquid)	Press. Gas (Liq.)		H280

• Transport Information: UN 1006; UN 1951

Discovery and Applications

Argon is a chemical element with the symbol Ar and atomic number 18. It is a noble gas, colorless, odorless, and chemically inert under standard conditions due to its complete valence electron shell. Argon occurs naturally in the Earth's atmosphere at approximately 0.93% by volume, making it the third most abundant gas after nitrogen and oxygen. It was first discovered in 1894 through the study of the residual gases remaining after nitrogen, oxygen, carbon dioxide, and other known components were removed from air.

Argon’s atomic structure gives it exceptional chemical stability. With a filled octet in its outer electron shell, argon does not readily form compounds under normal conditions, although some argon-containing compounds have been synthesized under extreme conditions in laboratories. Its inertness and non-reactivity are key properties that underlie its primary applications in industry and research.

One of the main applications of argon is as an inert shielding gas in welding and metal fabrication. In processes such as arc welding, argon prevents oxidation and contamination of the molten metal by displacing oxygen and other reactive gases. This property ensures high-quality welds and prevents structural defects in metals like aluminum, stainless steel, and titanium.

Argon is also used in the production of high-purity materials, such as semiconductors, where an inert atmosphere is required to avoid unwanted chemical reactions. It is employed in gas-filled incandescent and fluorescent light bulbs to prevent the oxidation of the filament and increase lifespan. In addition, argon is used in scientific research as a carrier or protective gas in gas chromatography, mass spectrometry, and other analytical techniques that require chemically inert conditions.

Another significant application of argon is in cryogenics. Liquid argon, obtained by cooling and compressing gaseous argon, serves as a refrigerant for low-temperature experiments and for preserving biological samples, including cells and tissues. Its low boiling point of –185.8 °C makes it suitable for maintaining ultra-low temperatures in laboratory and industrial settings.

Overall, argon is a stable, inert noble gas with wide-ranging applications in metallurgy, electronics, lighting, scientific research, and cryogenics. Its chemical inertness, abundance, and non-toxicity make it a valuable industrial and laboratory resource.

References

2025. Cold atmospheric plasma effectively kills chordoma cells through induction of intracellular reactive oxygen species. Scientific Reports.
DOI: 10.1038/s41598-025-05916-y

2025. Impact of discharge gas on a novel continuous flow in-liquid plasma discharge process for cobalt remediation and recovery from wastewater. Journal of Environmental Management.
DOI: 10.1016/j.jenvman.2025.125570

2025. Cold argon plasma-modified pea protein isolate: A strategy to enhance ink performance and digestibility in 3D-printed plant-based meat. International Journal of Biological Macromolecules.
DOI: 10.1016/j.ijbiomac.2025.144049