ASTM D5559

ASTM D5559 is the ASTM standard for determining acidity as free fatty acids or acid number in sulfonated and sulfated oils when ammonium or triethanolamine soaps are absent. It helps define a consistent test approach for evaluating acidic content in these materials, which is important for quality control, product comparison, and compliance-focused purchasing. By providing a common reference method, ASTM D5559 supports more reliable laboratory results and clearer technical communication between suppliers and users.

ASTM D5559 standard overview

The ASTM D5559 standard addresses how to measure acidity in sulfonated and sulfated oils using free fatty acids or acid number, with a specific limitation to samples that do not contain ammonium or triethanolamine soaps. That technical condition is important because it narrows the method’s intended use and helps keep results meaningful for the right material type. As a published ASTM standard, it serves as a practical test method for laboratories that need a defined, repeatable way to assess acid-related properties.

Where is ASTM D5559 used?

ASTM D5559 is typically used in laboratory and quality control settings that handle sulfonated and sulfated oils. It is relevant wherever these materials are tested for acidity as free fatty acids or acid number, including incoming inspection, batch release, and product evaluation workflows. The standard is especially useful when a consistent test method is needed for materials that fall within the scope described by the title and do not include ammonium or triethanolamine soaps.

Practical importance of ASTM D5559

The practical value of ASTM D5559 lies in helping users compare acidity results consistently across suppliers, lots, and test locations. A defined ASTM method reduces ambiguity in measurement and supports better decision-making in procurement, formulation review, and quality assurance. For organizations working with sulfonated or sulfated oils, using ASTM D5559 can also help reduce testing disputes and improve confidence in reported acid-related values.

• Acidity measured as free fatty acids or acid number
• Applies to sulfonated and sulfated oils
• Excludes ammonium or triethanolamine soaps
• Supports laboratory consistency and comparison
• Useful for quality control and product evaluation