ASTM D1218-21 PDF

Full title and description

ASTM D1218-21 — Standard Test Method for Refractive Index and Refractive Dispersion of Hydrocarbon Liquids. This standard describes manual (optical‑mechanical) and automatic (digital) procedures for measuring the refractive index (to four decimal places or better) and, where applicable, refractive dispersion of transparent and light‑colored hydrocarbon liquids. It is published by ASTM International as designation D1218‑21 (current edition published in 2021).

Abstract

This test method specifies how to measure the refractive index of hydrocarbon liquids in the approximate range 1.3300 to 1.5000 at controlled temperatures (nominally 20 °C to 30 °C), with an accuracy to the fourth decimal place. The manual optical‑mechanical procedure also covers refractive dispersion to the same precision. The method includes guidance on instrument verification and notes limitations (for example, strongly colored liquids, samples with bubble points near the test temperature, and situations where indices or temperatures lie outside the stated ranges).

General information

• Status: Active.
• Publication date: 1 November 2021 (designation D1218‑21).
• Publisher: ASTM International (American Society for Testing and Materials).
• ICS / categories: 75.080 (Petroleum products in general); related ICS for organic chemicals/measurement methods may apply.
• Edition / version: D1218‑21 (current revision published 2021; originally adopted 1952; replaces prior D1218 editions).
• Number of pages: 7 pages (concise test method).

Scope

The standard covers procedures to measure refractive index (to four decimal places or better) of transparent and light‑colored hydrocarbon liquids between about 1.3300 and 1.5000, at temperatures normally between 20 °C and 30 °C. The manual procedure also provides for measurement of refractive dispersion (fourth‑decimal precision). Users are warned that the method’s stated precision may not apply outside the nominal index or temperature ranges and that the method may be unsuitable for strongly colored liquids or those with bubble points close to the test temperature. It further explains the need for appropriate reference standards and instrument verification when extending measurement conditions.

Key topics and requirements

• Measurement of refractive index (n) to four decimal places (precision and bias statements provided in the standard).
• Usable index range typically 1.3300–1.5000; measurements outside that range may be possible but require validation.
• Temperature control of the sample (common test points between 20 °C and 30 °C) and reporting of test temperature with results.
• Manual (optical‑mechanical) and automatic (digital) refractometer procedures described, with instrument verification recommendations.
• Measurement of refractive dispersion (manual procedure) to the same precision where applicable.
• Sample limitations: intended for transparent/light‑colored hydrocarbons (liquid color typically limited to approximately No. 4 ASTM Color or lighter); strongly colored samples or those prone to weathering/bubbling at test temperature may be excluded.
• Significance: refractive index and dispersion are fundamental physical properties useful for identification, characterization, and quality control of pure hydrocarbons and mixtures.

Typical use and users

Laboratories and analysts in petroleum, petrochemical, lubricant and fuel testing, refinery quality control, research and development, and manufacturers of refractometer instruments commonly use this method. It is used for sample identification, routine QC checks, batch verification, and as a property incorporated into broader physicochemical characterizations of hydrocarbon products and blends.

Related standards

Referenced and related ASTM standards commonly cited with D1218 include Test Method D1500 (ASTM color of petroleum products), D1193 (reagent water), and practices for precision/bias and quality assurance such as D6299 and D6300. D1218‑21 is the 2021 revision of the D1218 series and replaces earlier editions (for example D1218‑12 / D1218‑16 editions).

Keywords

refractive index; refractive dispersion; refractometer; hydrocarbons; petroleum products; ASTM D1218; optical measurement; laboratory test method; quality control.

FAQ

Q: What is this standard?

A: ASTM D1218‑21 is a standardized laboratory test method for measuring the refractive index and refractive dispersion of hydrocarbon liquids, published by ASTM International in 2021.

Q: What does it cover?

A: It covers procedures (manual and automatic) to measure refractive index (to four decimal places) over the typical index range 1.3300–1.5000 and at controlled temperatures (normally 20 °C–30 °C), plus refractive dispersion via the manual procedure; it also states limitations and verification requirements for measurements outside nominal conditions.

Q: Who typically uses it?

A: Petroleum and petrochemical laboratory analysts, refinery and product quality control personnel, R&D chemists, and instrument manufacturers or calibration labs use this standard for product characterization and QC.

Q: Is it current or superseded?

A: As published November 1, 2021 (designation D1218‑21), this is the current active ASTM revision of D1218 and supersedes earlier editions (for example the 2012/2016 versions). Users should check with ASTM for any later revisions after 2021.

Q: Is it part of a series?

A: D1218 is part of the ASTM D02 committee family of standards (Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants) and is commonly used in conjunction with other D02 test methods and practices for petroleum testing and QC.

Q: What are the key keywords?

A: Refractive index; refractive dispersion; refractometer; hydrocarbons; petroleum; ASTM D1218; optical measurement; laboratory test method.