All Stopcocks and moveable joints in a vacuum system must be satisfactorily lubricated while remaining leak proof.  The ideal lubricant for this purpose would have a low vapor pressure and be stable, chemically inert, non-toxic, and easily applied/removed.   Apiezon greases have these qualities.  A wide range of greases are available for various applications.

Apiezon  Grease H

Apiezon Grease H will withstand temperatures up to 250C without melting.  In fact, it stiffens at temperatures above 40ºC.  It is of a rubbery nature and intended for lubricating glass taps and general purposes where a high melting point grease must be used.
 

Apiezon Grease L

Apiezon Grease L is a petrolatum hydrocarbon grease containing no additives. It has excellent vapor pressure capabilities, and is recommended for high vacuum use.   It is widely used in gas-liquid chromatography, and may be used on all ground joins in a vacuum system where it is essential to have a grease with good lubricating properties and a low vapor pressure.  It melts at 47ºC and should not be used where temperatures at joints are likely to be above 30ºC.
 

Apiezon Grease M

Apiezon Grease M is a general purpose grease for use in systems requiring a lubricant of moderate vapor pressure.  It is used whenever a good lubricant is required and is recommended for vacuum use and general O-ring use throughout the laboratory.  Grease M is not intended for use with joints that may exceed 30ºC.
 

Apiezon Grease N

Apiezon Grease N contains a high molecular weight polymeric additive that allows it to form a rubbery, cushioning effect between mating surfaces.  The physical nature of this product makes it a popular grease for high vacuum use as well as general purpose laboratory use.  It is not recommended for use above 30ºC. Vapor pressure is estimated to be 8x10^-10 torr at 20ºC.
 

Apiezon Grease T  can be used over a wider temperature range. It contains a gelling agent which, though not truly soluble in organic solvents, is readily dispersed by them; it is therefore easily cleaned from metal and glass surfaces by solvent action..