ASTM D1926-00(2006)
(Test Method)Standard Test Methods for Carboxyl Content of Cellulose
Standard Test Methods for Carboxyl Content of Cellulose
SIGNIFICANCE AND USE
These test methods measure the amount of carboxyl groups present in wood or cotton linter pulp. Carboxyl groups are indicative of the surface charge of the pulp which is a very important quantity for use in the papermaking industry.
SCOPE
1.1 These test methods cover the determination of the carboxyl content, or ion-exchange capacity, of cellulose from any source. Two test methods are described, the sodium chloride-sodium bicarbonate method () and the methylene blue method (). The test methods must be used within their limitations, and it must be recognized that there is no way of determining the accuracy of any method for the determination of carboxyl. The precision of the sodium chloride-sodium bicarbonate method is low in the lower range of carboxyl values. The methylene blue method can be used over the whole range of carboxyl values; it is especially useful in the low range. It is not applicable to the determination of carboxyl in soluble carbohydrate material. Although these test methods may be used to determine the ion-exchange capacity of unbleached pulps, the residual lignin will cause an undetermined error, especially the sulfonic acid groups in unbleached sulfite pulps ().
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D1926–00(Reapproved2006)
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 3. Significance and Use
1.1 These test methods cover the determination of the 3.1 These test methods measure the amount of carboxyl
carboxyl content, or ion-exchange capacity, of cellulose from groups present in wood or cotton linter pulp. Carboxyl groups
any source. Two test methods are described, the sodium are indicative of the surface charge of the pulp which is a very
chloride-sodium bicarbonate method (1) and the methylene important quantity for use in the papermaking industry.
blue method (2). The test methods must be used within their
4. Purity of Reagents
limitations, and it must be recognized that there is no way of
determining the accuracy of any method for the determination 4.1 Reagent-grade chemicals shall be used in all tests.
Unless otherwise indicated, it is intended that all reagents shall
of carboxyl. The precision of the sodium chloride-sodium
bicarbonate method is low in the lower range of carboxyl conform to the specifications of the Committee on Analytical
Reagents of the American Chemical Society, where such
values.Themethylenebluemethodcanbeusedoverthewhole
range of carboxyl values; it is especially useful in the low specifications are available. Other grades may be used, pro-
vided it is first ascertained that the reagent is of sufficiently
range. It is not applicable to the determination of carboxyl in
soluble carbohydrate material. Although these test methods high purity to permit its use without lessening the accuracy of
the determination.
may be used to determine the ion-exchange capacity of
unbleached pulps, the residual lignin will cause an undeter- 4.2 Unless otherwise indicated, references to water shall be
understood to mean reagent water conforming to Specification
mined error, especially the sulfonic acid groups in unbleached
sulfite pulps (3). D1193.
1.2 The values stated in SI units are to be regarded as
SODIUM CHLORIDE-SODIUM BICARBONATE
standard. No other units of measurement are included in this
METHOD
standard.
1.3 This standard does not purport to address all of the
5. Summary of Test Method
safety concerns, if any, associated with its use. It is the
5.1 In the sodium chloride-sodium bicarbonate method the
responsibility of the user of this standard to establish appro-
specimen is deashed with hydrochloric acid, washed, soaked in
priate safety and health practices and determine the applica-
sodium chloride-sodium bicarbonate solution, filtered, and an
bility of regulatory limitations prior to use.
aliquot of the filtrate titrated with 0.01 N hydrochloric acid to
a methyl red end point. The difference between the concentra-
2. Referenced Documents
3 tion of the filtrate and of the sodium chloride-sodium bicar-
2.1 ASTM Standards:
bonate solution is a measure of the ion-exchange capacity of
D1193 Specification for Reagent Water
the cellulose.
6. Reagents
These test methods are under the jurisdiction of ASTM Committee D01 on
Paint and Related Coatings, Materials, and Applications and are the direct
6.1 Hydrochloric Acid, Standard (0.01 N)—Prepare and
responsibility of Subcommittee D01.36 on Cellulose and Cellulose Derivatives.
standardize a 0.01 N solution of hydrochloric acid (HCl).
Current edition approved April 1, 2006. Published April 2006. Originally
approved in 1961. Last previous edition approved in 2000 as D1926 – 00. DOI:
10.1520/D1926-00R06.
2 4
The boldface numbers in parentheses refer to the list of references at the end of Reagent Chemicals, American Chemical Society Specifications, American
these test methods. Chemical Society, Washington, DC. For suggestions on the testing of reagents not
For referenced ASTM standards, visit the ASTM website, www.astm.org, or listed by the American Chemical Society, see Analar Standards for Laboratory
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Standards volume information, refer to the standard’s Document Summary page on and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
the ASTM website. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D1926–00 (2006)
6.2 Hydrochloric Acid (1 + 99)—Dilute 1 volume of con- carboxyl content. For pulps varying in carboxyl content from
centrated HCl (sp gr 1.19) with 99 volumes of water. 5.75 to 0.40 mmol/100 g pulp, the repeatability (intralabora-
6.3 Methyl Red Indicator Solution. tory) expressed as a percent coefficient of variance was 2.2 to
6.4 Sodium Chloride-Sodium Bicarbonate Solution— 8.1 %, respectively. Interlaboratory results based on different
Dissolve 5.85 g of sodium chloride (NaCl) and 0.84 g of materials and various test methods gave percent coefficient of
sodium bicarbonate (NaHCO ) in water and dilute to 1 L. variance of 9.0 to 33 % for these same materials.
6.5 Sodium Hydroxide Solution (0.4 g/L)—Dissolve0.4gof 10.2 No statement on bias can be made as no suitable
sodium hydroxide (NaOH) in water and dilute to 1 L. reference material exists for determining bias.
7. Procedure
METHYLENE BLUE METHOD
7.1 Condition the specimen in the atmosphere near the
11. Summary of Test Method
balance for at least 20 min before weighing duplicate portions
of 2.5 6 0.01 g. At the same time, weigh specimens for the
11.1 In the methylene blue method the specimen is treated
determination of moisture. Disintegrate the specimen in water,
with 0.0002 M methylene blue solution buffered to a pH of 8
filter through fritted glass, and disperse to about 1 % consis-
with diethylbarbituric acid (barbital). The decrease in methyl-
tencyinHCl(1 + 99)atroomtemperature.After2hcollectthe
eneblueconcentration,measuredphotometrically,isafunction
specimen on a fritted-glass filter funnel and wash with water
of the ion-exchange capacity of the cellulose.
saturated with carbon dioxide (CO ). Continue the washing
until the filtrate, after boiling, does not require more than 1 or 12. Apparatus
2dropsofNaOHsolutiontogiveanalkalinecolorwithmethyl
12.1 Spectrophotometer or Filter Photometer, capable of
red.
measuring absorbance near 620 mm.
7.2 Weigh the wet pulp pad, transfer it immediately to a
12.2 Shaker or Mixer for agitating the specimens in the
250-mL glass-stoppered Erlenmeyer flask, add 50 mL of the
methylenebluesolution.Awheelorrod,towhichthespecimen
NaCl-NaHCO solution with a pipet, and shake to obtain a
3 vials can be attached, that rotates at about 15 r/min, has proven
homogeneous slurry (Note 1).Allow the mixture to stand for 1
satisfactory.
h at room temperature. Filter through a clean, dry, fritted glass
12.3 Centrifuge, capable of settling the cellulose from the
funnel, pipet a 25-mLaliquot of the filtrate into an Erlenmeyer
methylene blue solution.
flask, and titrate with 0.01 N HCl, using methyl red solution as
an indicator. When the first change in color occurs, boil the
13. Reagents
solution for about 1 min to expel the carbon dioxide and
13.1 Buffer, Stock Solution—Dissolve 1.151 g of diethylbar-
continue the titration to a sharp end point.
bituric acid (barbital) in water, add the equivalent of 0.16 g of
NOTE 1—If the cation-exchange capacity is very low, use a solution sodium hydroxide using a standard solution and buret, and
containing about 5.85 g of NaCl and 0.42 g of NaHCO per litre. It is
dilute with water to 1 L in a volumetric flask.
importantthattheexcessofNaHCO belargeenoughthatthepHdoesnot
3 13.2 Hydrochloric Acid (1 + 99)—Dilute 1 volume of con-
fall below 7.0.
centrated hydrochloric acid (HCl, sp gr 1.19) with 99 volumes
7.3 Pipet 25 mL of the NaCl-NaHCO solution into an
of water.
Erlenmeyer flask and titrate as described in 7.2.
13.3 Methylene Blue, Stock Solution (0.002 M)—Dissolve
0.640 g of methylene blue in water, making allowance for
8. Calculation
moisture, and dilute to 1 L in a volumetric flask.
8.1 Calculate the cation-exchange capacity, c, of the speci-
NOTE 2—Information on the determination of the purity of methylene
men in milliequivalents per 100 g as follows:
blue is given in the literature (5).
av 2
c 5 b 2 a 2 (1)
S D
13.4 Methylene Blue—Buffer Solution (0.0002 M)—Mix 1
50 G
volume of methylene blue stock solution with 1 volume of
where:
buffer
...
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