Cargille refractive index (RI) liquids evolved from the Mineralogical industry where they were used in identification. Today they are standard tools in many laboratories in the fields of engineering, biology, optical analysis, forensics, instrumentation, cancer research and particle identification such as in the asbestos industry. There are over 250 refractive index liquids available and many more are custom formulated with materials research ongoing in order to provide RI liquids with extended ranges, smaller increments and higher degrees of accuracy. Chlorofluorocarbon (CFCs) components if used in Cargille RI liquids have physical properties that are harmless to the ozone layer, unlike those found in refrigerant gases, propellants and solvents which are destructive. The components used by Cargille Laboratories have vapour densities ten times that of air, are relatively non-volatile and have boiling points at least 10 degrees C higher than the highest boiling CFC listed for removal from commercial use by the Montreal Protocol. Their applications range from particle identification and optical analysis to fiber optics and mounting media.