Level Transmitter (Reed Chain)

Oil
Water
High and low pressure separators
Oil and water interface
Acids - hydrofluoric, hydrochloric, nitric, sulfuric, etc.
Refined petrochemical - gasoline, propane, butane, ethylene, etc.
Solvents - acetone, toluene, 
Gas condensate
Heat transfer fluids - diathermy, thermion and glycol
Black, green and red liquor
Refrigerants
Alcohols
Caustics
Chlorine
Steam condensate - boiler feedwater heater boiler drum level control
Bitumen
Vacuum tower bottoms
Ammonia
Most liquid to liquid interfaces