Galinstan

Galinstan is a liquid alloy of gallium, indium, and tin that remains liquid near room temperature. It is used where mercury’s toxicity makes mercury unsuitable.

Gallium: Gallium is a soft chemical element with a melting point just above typical room temperature. Gallium is the alloy’s main component and helps keep Galinstan liquid near room temperature.
Liquid-metal thermometer: A liquid-metal thermometer measures temperature through the expansion or movement of a conductive liquid metal. Galinstan is used as a mercury-free liquid in some thermometers.
Mercury: Mercury is a chemical element that is liquid at standard room temperature and is toxic, especially as vapor or certain compounds. Galinstan offers a lower-toxicity liquid-metal alternative, but is not a drop-in replacement in every device.
Alloy: An alloy is a material made from two or more elements, at least one of which is a metal. Galinstan is a multicomponent metallic alloy rather than a pure element.
Indium: Indium is a soft, silvery post-transition metal used in alloys, electronics, and coatings. Indium lowers the melting point of the gallium-based mixture.
Mercury-in-glass thermometer: A mercury-in-glass thermometer measures temperature through mercury’s expansion inside a sealed glass tube. Galinstan can replace the mercury, though its wetting behavior changes how the instrument must be designed.
Eutectic gallium-indium: Eutectic gallium-indium is a gallium–indium alloy that melts below room temperature. It is a closely related liquid alloy that lacks the tin present in Galinstan.
Eutectic system: A eutectic system is a mixture whose composition has the lowest melting temperature among its component mixtures. Eutectic behavior helps explain how metallic mixtures can melt below their pure components.
Tin: Tin is a malleable metal used in alloys, coatings, and solder. Tin combines with gallium and indium to form Galinstan’s liquid alloy.
Liquid metal cooling: Liquid metal cooling uses molten metals or alloys to transfer heat from a source. Galinstan’s liquid state and thermal conductivity make it a candidate coolant in experimental systems.

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Fusible alloyCompared with: Unlike most fusible alloys, it remains liquid around room temperature rather than melting during ordinary heating.