ASTM D1926-00(2019)

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.
Designation: D1926 − 00 (Reapproved 2019)
Standard Test Methods for
Carboxyl Content of Cellulose
This standard is issued under the fixed designation D1926; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 These test methods cover the determination of the 2.1 ASTM Standards:
carboxyl content, or ion-exchange capacity, of cellulose from D1193 Specification for Reagent Water
any source. Two test methods are described, the sodium
2 3. Significance and Use
chloride-sodium bicarbonate method (1) and the methylene
blue method (2). The test methods must be used within their
3.1 These test methods measure the amount of carboxyl
limitations, and it must be recognized that there is no way of groups present in wood or cotton linter pulp. Carboxyl groups
determining the accuracy of any method for the determination
are indicative of the surface charge of the pulp which is a very
of carboxyl. The precision of the sodium chloride-sodium important quantity for use in the papermaking industry.
bicarbonate method is low in the lower range of carboxyl
4. Purity of Reagents
values.Themethylenebluemethodcanbeusedoverthewhole
range of carboxyl values; it is especially useful in the low
4.1 Reagent-grade chemicals shall be used in all tests.
range. It is not applicable to the determination of carboxyl in
Unless otherwise indicated, it is intended that all reagents shall
soluble carbohydrate material. Although these test methods
conform to the specifications of the Committee on Analytical
may be used to determine the ion-exchange capacity of
Reagents of the American Chemical Society, where such
unbleached pulps, the residual lignin will cause an undeter-
specifications are available. Other grades may be used, pro-
mined error, especially the sulfonic acid groups in unbleached
vided it is first ascertained that the reagent is of sufficiently
sulfite pulps (3).
high purity to permit its use without lessening the accuracy of
the determination.
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
4.2 Unless otherwise indicated, references to water shall be
standard.
understood to mean reagent water conforming to Specification
D1193.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
SODIUM CHLORIDE-SODIUM BICARBONATE
responsibility of the user of this standard to establish appro-
METHOD
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
5. Summary of Test Method
1.4 This international standard was developed in accor-
5.1 In the sodium chloride-sodium bicarbonate method the
dance with internationally recognized principles on standard-
specimen is de-ashed with hydrochloric acid, washed, soaked
ization established in the Decision on Principles for the
in sodium chloride-sodium bicarbonate solution, filtered, and
Development of International Standards, Guides and Recom-
an aliquot of the filtrate titrated with 0.01 N hydrochloric acid
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
These test methods are under the jurisdiction of ASTM Committee D01 on Standards volume information, refer to the standard’s Document Summary page on
Paint and Related Coatings, Materials, and Applications and are the direct the ASTM website.
responsibility of Subcommittee D01.36 on Cellulose and Cellulose Derivatives. ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Current edition approved Dec. 1, 2019. Published December 2019. Originally Standard-Grade Reference Materials, American Chemical Society, Washington,
approved in 1961. Last previous edition approved in 2011 as D1926 – 00 (2011). DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
DOI: 10.1520/D1926-00R19. Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
The boldface numbers in parentheses refer to the list of references at the end of U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
these test methods. copeial Convention, Inc. (USPC), Rockville, MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1926 − 00 (2019)
to a methyl red end point. The difference between the concen-
b = millilitres of 0.01 N HCl consumed by 25 mL of the
tration of the filtrate and of the sodium chloride-sodium
NaCl-NaHCO solution.
bicarbonate solution is a measure of the ion-exchange capacity
of the cellulose. 9. Report
9.1 Until more data are obtained on the precision of this test
6. Reagents
method, it is suggested that the ion-exchange capacity be
6.1 Hydrochloric Acid, Standard (0.01 N)—Prepare and
reported to 0.01 milliequivalent/100 g of pulp.
standardize a 0.01 N solution of hydrochloric acid (HCl).
10. Precision and Bias
6.2 Hydrochloric Acid (1 + 99)—Dilute 1 volume of con-
centrated HCl (sp gr 1.19) with 99 volumes of water.
10.1 Work sponsored by ASTM, TAPPI, ACS, and ICCA
(see Ref 4) found that precision decreased with decreasing
6.3 Methyl Red Indicator Solution.
carboxyl content. For pulps varying in carboxyl content from
6.4 Sodium Chloride-Sodium Bicarbonate Solution—
5.75 to 0.40 mmol/100 g pulp, the repeatability (intralabora-
Dissolve 5.85 g of sodium chloride (NaCl) and 0.84 g of
tory) expressed as a percent coefficient of variance was 2.2 to
sodium bicarbonate (NaHCO ) in water and dilute to 1 L.
8.1 %, respectively. Interlaboratory results based on different
6.5 Sodium Hydroxide Solution (0.4 g/L)—Dissolve 0.4 g of
materials and various test methods gave percent coefficient of
sodium hydroxide (NaOH) in water and dilute to 1 L.
variance of 9.0 to 33 % for these same materials.
7. Procedure 10.2 No statement on bias can be made as no suitable
reference material exists for determining bias.
7.1 Condition the specimen in the atmosphere near the
balance for at least 20 min before weighing duplicate portions
METHYLENE BLUE METHOD
of 2.5 6 0.01 g. At the same time, weigh specimens for the
determination of moisture. Disintegrate the specimen in water,
11. Summary of Test Method
filter through fritted glass, and disperse to about 1 % consis-
11.1 In the methylene blue method the specimen is treated
tencyinHCl(1 + 99)atroomtemperature.After2hcollectthe
with 0.0002 M methylene blue solution buffered to a pH of 8
specimen on a fritted-glass filter funnel and wash with water
with diethylbarbituric acid (barbital). The decrease in methyl-
saturated with carbon dioxide (CO ). Continue the washing
eneblueconcentration,measuredphotometrically,isafunction
until the filtrate, after boiling, does not require more than 1 or
of the ion-exchange capacity of the cellulose.
2dropsofNaOHsolutiontogiveanalkalinecolorwithmethyl
red.
12. Apparatus
7.2 Weigh the wet pulp pad, transfer it immediately to a
12.1 Spectrophotometer or Filter Photometer, capable of
250-mL glass-stoppered Erlenmeyer flask, add 50 mL of the
measuring absorbance near 620 mm.
NaCl-NaHCO solution with a pipet, and shake to obtain a
12.2 Shaker or Mixer for agitating the specimens in the
homogeneous slurry (Note 1).Allow the mixture to stand for 1
methylenebluesolution.Awheelorrod,towhichthespecimen
h at room temperature. Filter through a clean, dry, fritted glass
vials can be attached, that rotates at about 15 r/min, has proven
funnel, pipet a 25-mLaliquot of the filtrate into an Erlenmeyer
satisfactory.
flask, and titrate with 0.01 N HCl, using methyl red solution as
an indicator. When the first change in color occurs, boil the 12.3 Centrifuge, capable of settling the cellulose from the
solution for about 1 min to expel the carbon dioxide and methylene blue solution.
continue the titration to a sharp end point.
13. Reagents
NOTE 1—If the cation-exchange capacity is very low, use a solution
13.1 Buffer, Stock Solution—Dissolve 1.151 g of diethylbar-
containing about 5.85 g of NaCl and 0.42 g of NaHCO per litre. It is
importantthattheexcessofNaHCO belargeenoughthatthepHdoesnot bituric acid (barbital) in water, add the equivalent of 0.16 g of
fall below 7.0.
sodium hydroxide using a standard solution and buret, and
dilute with water to 1 L in a volumetric flask.
7.3 Pipet 25 mL of the NaCl-NaHCO solution into an
Erlenmeyer flask and titrate as described in 7.2.
13.2 Hydrochloric Acid (1 + 99)—Dilute 1 volume of con-
centrated hydrochloric acid (HCl, sp gr
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