ASTM D1926-95
(Test Method)Standard Test Methods for Carboxyl Content of Cellulose
Standard Test Methods for Carboxyl Content of Cellulose
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 (1) and the methylene blue method (2). 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 (3).
1.2 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 1926 – 95
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Methods for
Carboxyl Content of Cellulose
This standard is issued under the fixed designation D 1926; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope Reagents of the American Chemical Society, where such
specifications are available. Other grades may be used, pro-
1.1 These test methods cover the determination of the
vided it is first ascertained that the reagent is of sufficiently
carboxyl content, or ion-exchange capacity, of cellulose from
high purity to permit its use without lessening the accuracy of
any source. Two test methods are described, the sodium
the determination.
chloride-sodium bicarbonate method (1) and the methylene
4.2 Unless otherwise indicated, references to water shall be
blue method (2). The test methods must be used within their
understood to mean reagent water conforming to Specification
limitations, and it must be recognized that there is no way of
D 1193.
determining the accuracy of any method for the determination
of carboxyl. The precision of the sodium chloride-sodium
SODIUM CHLORIDE-SODIUM BICARBONATE
bicarbonate method is low in the lower range of carboxyl
METHOD
values. The methylene blue method can be used over the whole
range of carboxyl values; it is especially useful in the low
5. Summary of Test Method
range. It is not applicable to the determination of carboxyl in
5.1 In the sodium chloride-sodium bicarbonate method the
soluble carbohydrate material. Although these test methods
specimen is deashed with hydrochloric acid, washed, soaked in
may be used to determine the ion-exchange capacity of
sodium chloride-sodium bicarbonate solution, filtered, and an
unbleached pulps, the residual lignin will cause an undeter-
aliquot of the filtrate titrated with 0.01 N hydrochloric acid to
mined error, especially the sulfonic acid groups in unbleached
a methyl red end point. The difference between the concentra-
sulfite pulps (3).
tion of the filtrate and of the sodium chloride-sodium bicar-
1.2 This standard does not purport to address all of the
bonate solution is a measure of the ion-exchange capacity of
safety concerns, if any, associated with its use. It is the
the cellulose.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
6. Reagents
bility of regulatory limitations prior to use.
6.1 Hydrochloric Acid, Standard (0.01 N)—Prepare and
standardize a 0.01 N solution of hydrochloric acid (HCl).
2. Referenced Documents
6.2 Hydrochloric Acid (1 + 99)—Dilute 1 volume of con-
2.1 ASTM Standards:
centrated HCl (sp gr 1.19) with 99 volumes of water.
D 1193 Specification for Reagent Water
6.3 Methyl Red Indicator Solution.
6.4 Sodium Chloride-Sodium Bicarbonate Solution—
3. Significance and Use
Dissolve 5.85 g of sodium chloride (NaCl) and 0.84 g of
3.1 These test methods measure the amount of carboxyl
sodium bicarbonate (NaHCO ) in water and dilute to 1 L.
groups present in wood or cotton linter pulp. Carboxyl groups
6.5 Sodium Hydroxide Solution (0.4 g/L)—Dissolve 0.4 g of
are indicative of the surface charge of the pulp which is a very
sodium hydroxide (NaOH) in water and dilute to 1 L.
important quantity for use in the papermaking industry.
7. Procedure
4. Purity of Reagents
7.1 Condition the specimen in the atmosphere near the
4.1 Reagent-grade chemicals shall be used in all tests.
balance for at least 20 min before weighing duplicate portions
Unless otherwise indicated, it is intended that all reagents shall
of 2.5 6 0.01 g. At the same time, weigh specimens for the
conform to the specifications of the Committee on Analytical
determination of moisture. Disintegrate the specimen in water,
These test methods are under the jurisdiction of ASTM Committee D-1 on Paint
and Related Coatings, Materials, and Applications and are the direct responsibility
Reagent Chemicals, American Chemical Society Specifications, American
of Subcommittee D01.36 on Cellulose and Cellulose Derivatives.
Current edition approved Nov. 10, 1995. Published January 1996. Originally Chemical Society, Washington, DC. For suggestions on the testing of reagents not
published as D 1926 – 61. Last previous edition D 1926 – 89. listed by the American Chemical Society, see Analar Standards for Laboratory
The boldface numbers in parentheses refer to the list of references at the end of Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
these test methods. and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
Annual Book of ASTM Standards, Vol 11.01. MD.
D 1926
filter through fritted glass, and disperse to about 1 % consis- with diethylbarbituric acid (barbital). The decrease in methyl-
tency in HCl (1 + 99) at room temperature. After 2 h collect the ene blue concentration, measured photometrically, is a function
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
2 drops of NaOH solution to give an alkaline color with methyl
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
methylene blue solution. A wheel or rod, to which the specimen
NaCl-NaHCO solution with a pipet, and shake to obtain a
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, frittedglass
funnel, pipet a 25-mL aliquot of the filtrate into an Erlenmeyer
12.3 Centrifuge, capable of settling the cellulose from the
flask, and titrate with 0.01 N HCl, using methyl red solution as
methylene blue solution.
an indicator. When the first change in color occurs, boil the
solution for about 1 min to expel the carbon dioxide and
13. Reagents
continue the titration to a sharp end point.
13.1 Buffer, Stock Solution—Dissolve 1.151 g of diethylbar-
NOTE 1—If the cation-exchange capacity is very low, use a solution
bituric acid (barbital) in water, add the equivalent of 0.16 g of
containing about 5.85 g of NaCl and 0.42 g of NaHCO per litre. It is
sodium hydroxide using a standard solution and buret, and
important that the excess of NaHCO be large enough that the pH does not
dilute with water to 1 L in a volumetric flask.
fall below 7.0.
13.2 Hydrochloric Acid (1 + 99)—Dilute 1 volume of con-
7.3 Pipet 25 mL of the NaCl-NaHCO solution into an
centrated hydrochloric acid (HCl, sp gr 1.19) with 99 volumes
Erlenmeyer flask and titrate as described in 7.2.
of water.
8. Calculation
13.3 Methylene Blue, Stock Solution (0.002 M)—Dissolve
0.640 g of methylene blue in water, making allowance for
8.1 Calculate the cation-exchange capacity, c, of the speci-
moisture, and dilute to 1 L in a volumetric flask.
men in milliequivalents per 100 g as follows:
av 2
NOTE 2—Information on the determination of the purity of methylene
c 5 b 2 a 2 (1)
S D
50 G
blue is given in the literature (5).
where:
13.4 Methylene Blue—Buffer Solution (0.0002 M)—Mix 1
G 5 weight of oven-dry specimen, g,
volume of methylene blue stock solution with 1 volume of
v 5 weight of water in the wet pulp pad, g,
buffer stock solution and dilute to a total of 10 volumes in a
a 5 millilitres of 0.01 N HCl consumed by 25 mL of
volumetric flask. The volume of solution to be prepared will
filtrate, and
vary with the requirements. For example, pipet 10 mL of each
b 5 millilitres of 0.01 N HCl consumed by 25 mL of the
solution into a 100-mL volumetric flask, dilute to the mark with
NaCl-NaHCO solution.
water, and mix thoroughly. Prepare a fresh solution for each
determination.
9. Report
9.1 Until more data are obtained on the precision of this test
14. Preparation of Calibration Curve for Ordinary Size
method, it is suggested that the ion-exchange capacity be
Specimens
reported to 0.01 milliequivalent/100 g of pulp.
14.1 In order to prepare a calibration curve, make up a series
10. Precision and Bias
of methylene blue buffer solutions containing the same amount
10.1 Work sponsored by ASTM, TAPPI, ACS, and ICCA
of buffer but different amounts of methylene blue, to cover the
(see Ref 4) found that precision decreased with decreasing
desired range. Add 50 mL of the stock solution of buffer to
carboxyl content. For pulps varying in carboxyl content from
each of nine 500-mL volumetric flasks. Add to these flasks 10,
5.75 to 0.40 mmol/100
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.