What is Galinstan?

A safer alternative to mercury

A traditional clinical thermometer. Image © Terence Bell

Galinstan® is a eutectic alloy composed of gallium, indium, and tin (hence its name, which is derived from the gallium, indium and stannum, the latin name for tin).

Although galinstan is a registered trademark of the German medical company Geratherm Medical AG, many other companies offer similar alloys, which are non-toxic and have a very low melt temperature.

These properties make galinstan an ideal substitute for mercury, particularly in clinical thermometers, but also in coolants and thermal grease and other applications where exposure is a risk.

Composition

There is no specific formula for galinstan, but a standard form is composed as follows:

  • Gallium (Ga): 68.5%
  • Indium (In): 21.5%
  • Tin (Sn): 10%

Indium Corporation produces a mercury substitute alloy that is composed of 61% gallium, 25% indium, 13% tin and 1% zinc, and has a melt temperature of roughly 45°F (7°C).

Properties

  • Appearance: Silvery metallic liquid
  • Odor: Odorless
  • Solubility: Insoluble in water and organic solvents
  • Specific Gravity: 6.4g/cc (room temperature)
  • Melting Point: 2.2°F (-19°C) Boiling Point: >2372°F (>1300°C)
  • Vapor Pressure: <10-8 Torr  (500°C)
  • Viscosity: 0.0024 Pa-s (room temperature)
  • Thermal conductivity: 16.5 (W-m-1-K-1)
  • Electrical Conductivity: 3.46×106 S/m (room temperature)
  • Surface Tension: s= 0.718 N/m (room temperature)

Benefits

Galinstan medical thermometers are considered more accurate than traditional mercury thermometers and much safer, as

galinstan alloy is non-toxic and can be safely cleaned in cases of breakage.

Also, as opposed to mercury, disposal of galinstan and galinstan thermometers does not pose any serious environmental threat.

Other

According to Geratherm Medical, galinstan was awarded the gold medal for best new invention at the 1993 "Eureka" Inventors' Fair in Brussels.