CHARLES D. WINTERS / SCIENCE PHOTO LIBRARY CHARLES D. WINTERS / SCIENCE PHOTO LIBRARY
Helium vessel. Container holding liquid helium, a substance used as a refrigerant in low temperature research; gaseous helium is also liquified when large amounts are being transported. Helium liquifies at -268.9 degrees Celsius (C) and must be cooled to -272.2 C at a pressure of 25 atmospheres before it will solidify; these temperatures are only just above absolute zero (- 273.18 C). If liquid helium is cooled to -270.98 C it greatly changes its properties and is known as Helium II. Helium II has a high thermal conductivity, no internal temperature differences and zero viscosity. The main source of helium is natural gas, in which it is an impurity.
Model release not required. Property release not required.