Refractive Index in the Petrochemical, Automotive, and Aviation Industries

Refractive Index in the petrochemical, automotive, and aviation industries is used for characterisation, concentration determination, and the end product stability of lubricating oils, fuels, oils, wax, lubricants, deicing and anti-freeze agents, and more. Measuring the Refractive Index is also the method used for quality control of operating fluids for machines and engines, as well as AdBlue, the synthetic urea solution for treating diesel engine emissions.

Standard Test Methods for Refractive Index

ASTM D1218-12:2016 Standard Test Method for Refractive Index and Refractive Dispersion of Hydrocarbon Liquids

Refractive index and refractive dispersion are fundamental physical properties, which can be used in conjunction with other properties to characterize pure hydrocarbons and their mixtures.

This test method covers the measurement of refractive index, accurate to four decimal places or better, of transparent and light-colored hydrocarbons in the range of 1.3300 to 1.5000 at temperatures from 20°C to 30°C by manual (optical-mechanical) or automatic (digital) procedure.

ASTM D1747-09:2014 Standard Test Method for Refractive Index of Viscous Materials

The use of refractive index in correlative methods for the determination of the gross composition of viscous oils and waxes often requires its measurement at elevated temperatures.

This test method covers the measurement of refractive indexes, accurate to two units in the fourth decimal place of transparent and light-colored viscous hydrocarbon liquids and melted solids.

ASTM D3321-19:2019 Standard Test Method for Use of the Refractometer for Field Test Determination of the Freezing Point of Aqueous Engine Coolants

This practice is commonly used by vehicle service personnel to determine the freezing point, in degrees Celsius or Fahrenheit, of aqueous solutions of commercial ethylene and propylene glycol-based coolant. A durable hand-held refractometer is available that reads the freezing point, directly, in degrees Celsius or Fahrenheit, when a few drops of engine coolant are properly placed on the temperature-compensated prism surface of the refractometer. This refractometer is for glycol and water solutions and is not suitable for other coolant solutions.

This test method covers the use of a portable refractometer for determining the approximate freezing protection provided by ethylene and propylene glycol-based coolant solutions as used in engine cooling systems and special applications.

ASTM D5006-11:2016 Standard Test Method for Measurement of Fuel System Icing Inhibitors (Ether Type) in Aviation Fuels

Diethylene Glycol Monomethyl Ether (DiEGME) is miscible with water and can be readily extracted from the fuel by contact with water during shipping and in storage. Methods are therefore needed to check the additive content in the fuel to ensure proper additive concentration in the aircraft.

This test method is applicable to analyses performed in the field or in a laboratory and covers a technique for measuring the concentration of DiEGME in aviation fuels. A measured volume of fuel, extracted with a fixed ratio of water, is tested with a suitable refractometer to determine the concentration of fuel system icing inhibitor (FSII) in fuel. Precision estimates have been determined for the DiEGME additive using specific extraction ratios with a wide variety of fuel types. The extraction ratios are high enough that portable handheld refractometers can be used, but not so high as to sacrifice accuracy or linearity, or both, in the 0.01% to 0.25% by volume range of interest.

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