ASTM D6304-25 PDF

Full title and description

ASTM D6304-25 — Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration. This standard describes coulometric Karl Fischer procedures (direct titration and indirect determination after thermal extraction/vaporization) for measuring entrained and dissolved water in a wide range of petroleum-related fluids and additives.

Abstract

ASTM D6304-25 specifies coulometric Karl Fischer titration methods for the quantitative determination of water in petroleum products, lubricating oils, additives and related hydrocarbons. It includes direct injection procedures and indirect oven/vaporization techniques for samples where direct titration is impractical. The standard defines applicability ranges, typical precision limits for the prescribed procedures, and known interferences (for example, mercaptans, sulfides and other sulfur species).

General information

• Status: Active (current ASTM designation: D6304-25).
• Publication date: 2025 (D6304-25 — active edition; ASTM record last updated July 29, 2025).
• Publisher: ASTM International (American Society for Testing and Materials).
• ICS / categories: 71.040.50 (physicochemical methods of analysis); 75.080 (petroleum products in general); 75.100 (lubricants, industrial oils and related products).
• Edition / version: D6304-25 (2025 edition).
• Number of pages: 10 pages (typical published PDF length for this edition).

Scope

This test method covers the direct determination of entrained water in petroleum products and hydrocarbons using automated coulometric Karl Fischer instrumentation and also covers indirect analysis of water thermally removed from samples and swept with dry inert gas into the Karl Fischer titration cell. The method is applicable to additives, lube oils, base oils, automatic transmission fluids, hydrocarbon solvents and other petroleum products; by choice of sample size it can be applied from mg/kg up to percent-level concentrations. The standard also notes known interfering substances and gives precision statements for the specified procedures.

Key topics and requirements

• Measurement principle: coulometric Karl Fischer titration (iodine generated coulometrically; end point by electrometric detection).
• Procedures: direct titration (injection of sample into titration vessel) and indirect/thermal extraction (oven or vaporizer with carrier gas into KF cell).
• Analytical range and recommended sample sizes to cover mg/kg to percent water concentrations; precision statements for Procedures A, B and C are provided in the standard.
• Interferences and limitations: identifies substances (e.g., mercaptans, sulfides, elemental sulfur) known to interfere and provides guidance on handling problem matrices.
• Use of commercial coulometric reagents and instrumentation; recommendations for sample handling, conditioning and safety considerations for KF reagents and volatile samples.

Typical use and users

Used routinely by chemical and oil-analysis laboratories, quality control teams in petroleum refining and lubricant manufacturing, additive suppliers, testing service providers, and research laboratories. Typical applications include incoming/outgoing QC for base oils and lubricants, monitoring moisture in hydrocarbon solvents, validation of drying processes, and forensic/failure analysis where moisture content affects performance.

Related standards

Commonly referenced companion and related methods and practices include ASTM D1193 (reagent water), ASTM D4052 (density by digital density meter), ASTM D4175 (terminology), ASTM E203 (volumetric Karl Fischer titration — alternative KF method), and related ASTM practices for sampling and precision/bias evaluation (e.g., D4057, D6300, D6299). These documents are often cited together in laboratory procedures and proficiency testing programs.

Keywords

Karl Fischer; coulometric titration; water determination; moisture analysis; petroleum products; lubricating oils; additives; water vaporizer; Karl Fischer oven; moisture interferences.

FAQ

Q: What is this standard?

A: ASTM D6304-25 is the 2025 edition of the ASTM standard that specifies coulometric Karl Fischer titration procedures for determining water in petroleum products, lubricating oils and additives.

Q: What does it cover?

A: It covers both direct coulometric titration (sample injected into the KF cell) and indirect methods where water is thermally extracted/vaporized from the sample and carried into the titration cell by dry inert gas; the standard gives applicability ranges, precision information, and notes known interferences.

Q: Who typically uses it?

A: Analytical and QC laboratories in the petroleum, lubricant and additives industries, contract testing laboratories, research groups and any organization that needs reliable moisture measurements in hydrocarbon matrices.

Q: Is it current or superseded?

A: The -25 edition (D6304-25) is the current active edition designated for 2025; earlier editions include D6304-20, D6304-16 and prior revisions. Check ASTM International or official document summaries for the latest status/updates.

Q: Is it part of a series?

A: D6304 is part of the ASTM D02 committee portfolio (petroleum products, liquid fuels and lubricants) and is commonly used alongside other D02 analytical and sampling standards (for example, D4052, D1193, D4057, and E203).

Q: What are the key keywords?

A: Coulometric Karl Fischer, water determination, moisture analysis, petroleum, lubricants, additives, water vaporizer, Karl Fischer oven, coulometric titration.