ASTM D1218 Refractive Index and Refractive Dispersion of Hydrocarbon Liquids
The characteristic appearance of a transparent liquids is partially determined by its refractive index, or ability to bend light. Refractive indexes of lubricants and hydrocarbons tend to increase with average molecular weight, density, purity and degree of saturation. This test determines the refractive index of liquids. It may be used as a quality control tool or to compare homologous series of compounds. It is appropriate for liquids with no suspended particles at the test temperature.
The refractometer used in this test consists of a prism box, an adjustable telescopic eyepiece and a sodium arc lamp. The sample is placed in the prism box and brought to the test temperature. The telescopic eyepiece is adjusted to determine the angle at which light just passes through the sample. This is compared to a calibration curve created using a known standard and reported as a unitless number. Please specify the desired temperature.