4.1 This test method is not appropriate for alkali-soluble resins whose acid functionality is due to incorporated anhydrides. Variations in manufacture, storage, and possible contamination of anhydride functional resins may cause partial hydrolysis, or esterification, which will invalidate data from this test method. Anhydride functional resins should be characterized by Test Method D3644.

4.2 This test method is used to measure a property of acid functionalized resins. Acid number determines the utility of resins as well as being a significant quality control measure.

1.1 This test method covers the measurement of the free acidity present in certain alkali-soluble resins.

1.2 This test method is not suitable for styrene-maleic anhydride resins.

1.3 The resin manufacturer should specify whether or not this test method may be used for his product(s).

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 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.

1.6 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.