liquidhelium

Liquidhelium is the liquid form of the element helium, a noble gas. It is colorless, odorless, non-toxic, and chemically inert. Commercial liquid helium is predominantly helium-4, with smaller amounts of helium-3 used for specialized research.

At standard atmospheric pressure, helium-4 becomes a liquid at about 4.2 kelvin, while helium-3 liquefies at around 3.2 kelvin. Both remain liquid at lower temperatures, but solidification requires substantial pressure; helium is one of the few substances that cannot be solidified at low temperature without high pressure.

A defining property of liquid helium is its quantum behavior. Helium-4 becomes a superfluid (He II) below 2.17 K, exhibiting zero viscosity and extremely high thermal conductivity. Helium-3 also forms a superfluid, but only at millikelvin temperatures and through a different quantum mechanism. Mixtures of helium-3 and helium-4 enable ultra-low-temperature cooling via dilution refrigerators, reaching tens of microkelvin.

Liquid helium has a very low boiling point and a small latent heat of vaporization. It expands dramatically when warmed to room temperature, by roughly 700 times its liquid volume. It is stored in insulated dewars and handled with cryogenic equipment to minimize loss.

Production and supply mainly rely on extraction from natural gas fields, where helium accumulates as a byproduct. It is captured, purified, and cryogenically separated for liquefaction. Because helium is relatively scarce, its price and availability can be volatile and its use is closely managed in research and industry.

Applications include cooling superconducting magnets in MRI and NMR systems, particle accelerators, and cryogenic research. Liquid helium remains essential for reaching ultra-low temperatures in scientific experiments and technology.