4.1 This test method measures a fundamental property of matter which is useful for the control of purity and composition for simple identification purposes, and for optical parts design. This test method is capable of readability to four figures to the right of the decimal point.

1.1 This test method covers a procedure for measuring the index of refraction of transparent organic plastic materials.

1.2 A refractometer method is presented. This procedure will satisfactorily cover the range of refractive indices found for such materials. Refractive index measurements require optically homogeneous specimens of uniform refractive index.

Note 1: This test method and ISO 489 are technically equivalent.

1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.