4.1 Anion impurities in caustic soda and caustic potash are monitored by manufacturers and users for quality control of the products. Anions of primary interest are chloride, chlorate, and sulfate. This test method has determined precision estimates only for these three impurities.

1.1 This test method covers the determination of anionic impurities in 50 % caustic soda (sodium hydroxide) and 50 % caustic potash (potassium hydroxide) solutions using ion chromatography (IC). Anions that can be determined at concentrations of approximately 0.1 to 1000 ug/g (ppm) include: bromide, chlorate, chloride, fluoride, nitrate, phosphate, and sulfate.

1.2 By varying the sample size, this test method can be used for anhydrous caustic soda and caustic potash products, as well as other concentrations of liquid products.

1.3 This test method is not intended to be used to quantify chloride in caustic soda where the sodium chloride concentration is approximately 1 %. For the most accurate determinations, it is recommended that high concentrations of chloride be analyzed using a potentiometric titration procedure, such as the one described in Test Methods E291.

1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.

1.5 Review the current appropriate Safety Data Sheets (SDS) for detailed information concerning toxicity, first aid procedures, and safety precautions.

1.6 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 and health practices and determine the applicability of regulatory limitations prior to use. Specific hazards statements are given in Section 8.