ASTM D1807 Test Methods for Refractive Index and Specific Optical Dispersion
ASTM D1807 Standard Test Methods for Refractive Index and Specific Optical Dispersion of Electrical Insulating Liquids
1. Scope
1.1 These test methods cover the determination of the refractive index and the specific optical dispersion of electrical insulating liquids such as are used in capacitors, transformers, circuit breakers, and oil-filled cables.
1.2 Two test methods are described, a routine method and a more precise referee method. Both methods are applicable to transparent, light-colored, insulating liquids.
1.2.1 The routine method is used to determine refractive index and specific optical dispersion as described in these test methods.
1.2.2 The referee method is used when a test of high accuracy is desired. These methods are described in Test Method D1218. Specific optical dispersion is calculated by dividing the refractive dispersion value determined in Test Method D1218 by the relative density (specific gravity) (see Test Method D1298) of the liquid under test.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D1218 Test Method for Refractive Index and Refractive Dispersion of Hydrocarbon Liquids
D1298 Test Method for Density, Relative Density (Specific Gravity), or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method
3. Terminology
3.1 Definitions:
3.1.1 refractive index, n - the ratio of the velocity of light in air to its velocity in the substance under test.
3.1.2 relative density (specific gravity), n - the ratio of the mass of a given volume of liquid at 15°C (60°F) to mass of an equal volume of pure water at the same temperature.
3.1.3 specific optical dispersion, n - the difference between the refractive indexes of light of two different wavelengths, both indexes measured at the same temperature, and divided by the relative density (specific gravity), also measured at the test temperature.
