Meaning and use

These test methods measure the amount of carboxyl groups present in wood or lint pulp. The carboxyl group represents the surface charge of the pulp, which is a very important amount used in the paper industry.

ASTM D1926-2011 Standard Test Method for Carboxyl Content of Cellulose

Step 1: Scope

1.1 These test methods include the determination of the carboxyl content or ion exchange capacity of cellulose from any source. Two test methods, sodium chloride-sodium bicarbonate method (1) and methylene blue method (2), are described. Test methods need to be used within their limitations, and it needs to be recognized that the accuracy of any method for determining carboxyl groups cannot be determined. In the lower carboxyl group value range, the sodium chloride-sodium bicarbonate method is less accurate. The methylene blue method can be used for the whole range of carboxyl group values. It is particularly useful at low ranges. It is not suitable for the determination of carboxyl groups in soluble carbohydrate materials. Although these test methods can be used to determine the ion exchange capacity of unbleached pulp, residual lignin will lead to uncertain errors, especially sulfonic acid groups in unbleached sulfite pulp (3).

1.2 Values expressed in SI units shall be regarded as standard values. No other units of measurement are included in this standard.

1.3 This standard is not intended to address all safety concerns, if any, associated with its use. It is the responsibility of users of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory restrictions prior to use.