ISO 3681:2018

This document specifies a titrimetric method for determining the esterified-acid content in binders for paints and varnishes, free acids and acid anhydrides being necessarily included in the result obtained.
Because different binders vary in their resistance to saponification, this document is of limited applicability. If necessary, completeness of saponification can be checked by repeating the test under more severe conditions achieved by the use of longer saponification time, more concentrated potassium hydroxide solution, or a higher-boiling alcohol as solvent.
Annex A specifies a procedure suitable for binders that saponify with difficulty.
The method is not applicable to those materials that show further reaction with alkalis beyond normal saponification.