Diffusion Pump Fluid.
Thermal stability; resists oxidation; chemically inert
Dow Corning 702 Diffusion Pump Fluid is a general-purpose fluid designed for fast pumping of large volumes of gas. It is used to produce vacuums in the range of 10-5 to 10-7 torr. It is also used in vapor ejector pumps that attain vacuums of 10-4 to 10-5 torr.