ASTM D3516-89(1995)e1
(Test Method)Standard Test Methods for Ashing Cellulose
Standard Test Methods for Ashing Cellulose
SCOPE
1.1 These test methods cover four ashing methods for cellulose. These are intended for use on unbleached and bleached cellulose in sheeted or bulk fiber form. Each one of the test methods has advantages, so that preference applications exist for all four.
1.2 The test methods appear as follows:SectionsTest Method A-Ash in Cellulose at 575oC6 to 11Test Method B-Sulfated Ash in Cellulose at 575oC12 to17Test Method C-Ashing Cellulose by Schoniger Oxidation18 to 22Test Method D-Wet Ashing of Cellulose for Inorganics23 to 29
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 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. For a specific hazard statement, see 20.6.1.
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e1
Designation: D 3516 – 89 (Reapproved 1995) An American National Standard
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
Ashing Cellulose
This standard is issued under the fixed designation D 3516; 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.
e NOTE—Keywords and unit of measurement statement were added editorially in June 1995.
The weight of ash obtained varies with the temperature of ignition. Higher
1. Scope
temperatures (850°C) will convert calcium carbonate and other carbonates
1.1 These test methods cover four ashing methods for
to the oxides and thus give lower values for ash. The composition of ash
cellulose. These are intended for use on unbleached and
may vary with the pulping process employed for manufacture, which
bleached cellulose in sheeted or bulk fiber form. Each one of
limits the significance of the ash determination in absolute terms.
the test methods has advantages, so that preference applica-
3.2 Test Method B, Sulfated Ash in Cellulose at 575°C—In
tions exist for all four.
this ashing procedure the metal salts are converted to sulfates
1.2 The test methods appear as follows:
by treatment with sulfuric acid and ignition at 575 6 25°C to
Sections
overcome limitations of Test Method A. It should not be
Test Method A—Ash in Cellulose at 575°C 6 to 11
considered as a standard preparative test method for elemental
Test Method B—Sulfated Ash in Cellulose at 575°C 12 to 17
Test Method C—Ashing Cellulose by Schoniger Oxidation 18 to 22
analysis.
Test Method D—Wet Ashing of Cellulose for Inorganics 23 to 29
NOTE 2—Conventional dry ashing at high temperature (over 850°C)
1.3 The values stated in SI units are to be regarded as the
results in loss of carbon dioxide from metal carbonates, decomposition of
standard. The values given in parentheses are for information
magnesium sulfate, and loss of sodium salts. Ashing at lower temperatures
only. (575°C) gives a better estimate of the inorganic impurities, but has the
disadvantage of requiring a long ignition time and also the heat produced
1.4 This standard does not purport to address all of the
by the burning pulp can raise the temperature far above 575°C for a short
safety concerns, if any, associated with its use. It is the
period of time, converting calcium carbonate to the oxide in varying
responsibility of the user of this standard to establish appro-
amounts. The sulfated ash method overcomes these objectionable features
priate safety and health practices and determine the applica-
and has additional advantages. It is relatively insensitive to ignition time.
bility of regulatory limitations prior to use. For a specific
Ash weight remains constant during weighing, and because the ash does
hazard statement, see Note 12.
not melt it will not attack the crucible.
3.3 Test Method C, Ashing Cellulose by Schoniger
2. Referenced Documents
Oxidation—This test method is generally applicable to ashing
2.1 ASTM Standards:
cellulose for subsequent analysis of inorganic constituents. The
D 1193 Specification for Reagent Water
procedure utilizes the Schoniger technique in which the cellu-
D 1348 Test Methods for Moisture in Cellulose
lose is burned in a combustion flask and all combustion
products are dissolved in an aqueous medium, thus avoiding
3. Summary of Test Methods
the possibility of physical loss of sample such as can occur in
3.1 Test Method A, Ash in Cellulose at 575°C—This test
dry ashing (Test Methods A and B). A limitation is the
method measures the ash content of cellulose, which is defined
relatively small sample of 1 g, which can be ashed without
for this test as the residue remaining after ignition at 575 6
excessively large apparatus in which to carry out the oxidation
25°C until all carbon has been burned off. It is the simplest of
step. Small specimens may not be adequately representative
the four test methods for the determination of ash content only,
where a particulate contaminate is involved.
and it should not be considered as a standard preparative
3.4 Test Method D, Wet Ashing of Cellulose for
procedure for elemental analysis.
Inorganics—This test method is recommended for ashing
NOTE 1—The ash content at this ignition temperature is a reasonable
cellulose for subsequent analysis of inorganic constituents. The
measure of the mineral salts and inorganic foreign matter in the cellulose.
procedure employs saturation of the cellulose with a concen-
trated solution of hydrogen peroxide followed by incremental
These test methods are under the jurisdiction of ASTM Committee D-1 on Paint addition to a small volume of concentrated sulfuric acid. It has
and Related Coatings, Materials, and Applications and are the direct responsibility
the advantage over Test Method C of not requiring special
of Subcommittee D01.36 on Cellulose and Cellulose Derivatives.
apparatus and can be readily applied to samples of 5 to 10 g.
Current edition approved Oct. 27, 1989. Published December 1989. Originally
The test method becomes tedious and less convenient for use
published as D 3516 – 76. Last previous edition D 3516 – 76 (1985).
Annual Book of ASTM Standards, Vol 11.01.
where larger specimens such as 50 or 100 g are required.
Annual Book of ASTM Standards, Vol 06.03.
D 3516
Specimens this large, although not generally required, may be should be varied so that the weight of the ash will be not less
necessary for the determination of trace levels of constituents than 10 mg and preferably over 20 mg. Table 1 gives suggested
such as manganese or silica. Smaller samples may not be sample sizes.
adequately representative where a particulate contaminate is
7.2 Selection of the specimen shall be in such a manner as
involved.
to be representative of the lot being tested.
4. Significance and Use NOTE 4—No set sampling procedure has been established to be
applicable to all samples. It will suffice to specify that the specimen shall
4.1 Ash content gives an estimation of the inorganic content
be representative of the lot being sampled.
of cellulose samples. The presence of high levels of ash can be
expected to be detrimental to the process of making cellulose
8. Procedure
derivatives. It also provides a rough estimate of silica content
8.1 Weigh out, to the nearest 0.05 g, sufficient cellulose to
which can have a significant effect on the performance of filters
give the correct range of ash weight (see Table 1). At the same
in cellulose derivative manufacturing facilities.
time, a separate specimen (3 to 5 g) should be weighed and
5. Purity of Reagents dried at 105°C for a moisture determination.
5.1 Reagent grade chemicals shall be used in all tests.
NOTE 5—Test Methods D 1348, Method B is suitable. However,
Unless otherwise indicated, it is intended that all reagents shall
accuracy of the moisture test is not critical for the ash determination and
any method capable of obtaining the percent oven dry within 0.5 % of the
conform to the specifications of the Committee on Analytical
true value is adequate.
Reagents of the American Chemical Society, where such
specifications are available. Other grades may be used, pro-
8.2 Heat the platinum dish in the muffle furnace at 575°C
vided it is first ascertained that the reagent is of sufficiently
for 15 min, cool and weigh to the nearest 0.1 mg. Place the
high purity to permit its use without lessening the accuracy of
weighed cellulose in the platinum dish and place the dish on
the determination.
the open door of the muffle furnace, previously set and allowed
5.2 Purity of Water—Unless otherwise indicated, references
to reach equilibrium at 575°C. Allow the cellulose to char
to water shall be understood to mean reagent water as defined
without flame by gradually moving the dish into the muffle,
in Specification D 1193.
and continue ashing with the door closed for 1 h.
TEST METHOD A—ASH IN CELLULOSE AT 575°C
NOTE 6—With some pulps, the character of the ash inhibits complete
carbon removal and gray or black specks persist after3hof ignition. The
6. Apparatus
addition of a few drops of distilled water to the ash after 8.3 followed by
drying and reignition at 575°C for1hor more may be required. Extreme
6.1 Balance, with an accuracy to 0.05 g is required for
cases may require a second treatment with water.
weighing cellulose samples.
NOTE 7—If the sample is too large, either separate ashings are required
6.2 Analytical Balance, with a sensitivity of 0.1 mg is
or successive additions of cellulose are made with extreme care so as not
required. It should be checked with Class S weights.
to disturb the ash. 8.2 is then repeated between each addition.
6.3 Drying Oven, with the capability of maintaining a
8.3 Remove the dish from the muffle furnace and allow to
temperature of 105 6 2°C.
cool somewhat. Place it in the desiccator and allow it to cool to
6.4 Desiccator, such as silica gel, indicating drierite, or
room temperature.
magnesium perchlorate are suitable.
6.5 Muffle Furnace, electric, capable of maintaining a tem-
NOTE 8—Care must be taken at all times to keep drafts away from the
perature of 575 6 25°C, is recommended.
light, fluffy ash.
NOTE 3—Back to front temperatures in muffle furnaces frequently
8.4 Weigh the dish and ash to the nearest 0.1 mg. Reignite
exceed the6 25°C range, so that operating limits should be established for
for a 15-min period and reweigh. Repeat as required to obtain
a given furnace.
constant weight.
6.6 Dish, platinum, 100-mL capacity or larger. Porcelain
crucibles are not recommended.
9. Calculation
6.7 Tongs, approximately 0.5 m (20 in.) long, with nickel-
9.1 Calculate the ash percent of moisture-free cellulose, E,
chromium or platinum tips.
as follows:
7. Test Specimen
~C 2 B!~100!~100!
E 5 (1)
~A! ~D!
7.1 The amount of cellulose selected for each ash determi-
nation depends on the ash content of the test specimen and
TABLE 1 Suggested Sample Sizes
Reagent Chemicals, American Chemical Society Specifications, American
Ash, % Moisture-Free Cellulose, g
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
Over 0.5 5
listed by the American Chemical Society, see Analar Standards for Laboratory
0.20 to 0.5 10
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
0.12 to 0.2 20
and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
0.08 to 0.12 30
MD.
5 0.04 to 0.08 40
Suitable apparatus is available from A. H. Thomas Co., Vine St. at 3rd, P. O.
Less than 0.04 50
Box 779, Philadelphia, PA 19105.
D 3516
14.6 After the last trace of carbon has disappeared, ignite in
where:
the muffle furnace for1hat 575°C.
A 5 weight of specimen as is, g,
14.7 Remove the dish and allow it to cool somewhat before
B 5 weight of dish, g,
C 5 weight of dish plus ash, g, and placing it in desiccator and cooling to room temperature.
D 5 oven dry cellulose in specimen, %
14.8 Weigh the dish and sulfated ash to the nearest 0.1 mg.
Reignite for a 15-min period and reweigh. Repeat as required
10. Report
to obtain constant weight.
10.1 Report the results to the nearest 0.01 %. Duplicate
NOTE 10—To remove the ash from the dish, clean with boiling
determinations should check within approximately 5 %.
hydrochloric acid.
NOTE 11—On igniting sulfated ash at 575°C, there should be no fusion
11. Precision and Bias
with the dishes, even when ashing cellulose that gives an alkaline ash.
11.1 A precision of 8 % relative at the 95 % confidence level
14.9 Prepare a reagent blank for the H SO corresponding
2 4
is found for specimens at the 0.05 % ash level.
to the number of millilitres of H SO used in 14.4 and 14.5, by
2 4
11.2 No statement of bias can be made as no suitable
the addition of the acid to a platinum dish after ignition and
reference material exists for determining bias.
true weight was determined, and carrying through 14.4-14.8 as
they apply.
TEST METHOD B—SULFATED ASH IN
CELLULOSE AT 575°C
15. Calculation
15.1 Calculate the sulfated ash, S, as percent of moisture-
12. Apparatus and Reagent
free cellulose, as follows:
12.1 Hot Plate.
~C 2 B 2 R!~100!~100!
12.2 Additional apparatus shall be in accordance with Sec-
S 5 (4)
~A! ~D!
tion 6.
12.3 Sulfuric Acid—Concentrated H SO .
2 4 where:
A 5 weight of specimen, g,
13. Test Specimen
B 5 weight of dish, g,
C 5 weight of dish plus sulfated ash, g,
13.1 The amount of cellulose selected for each ash deter-
R 5 weight of H SO reagent blank residue, g, and
mination depends upon the sulfated ash content of the test 2 4
D 5 oven-dry cellulose in specimen, %.
specimen and should be varied so that the weight of the ash
will be not less than 10 mg and preferably over 20 mg. Table
16. Report
1 gives suggested specimen sizes for Test Method A. The table
16.1 Report the results to the nearest 0.01 %. Duplicate
is applicable to sulfated ash also, providing the percent ash
determinations should check within approximately 5 %.
column is taken as percent sulfated ash.
NOTE 9—The sulfated ash values will be higher than the ash obtained
17. Precision and Bias
by ignition of the cellulose without addition of the sulfuric acid. The
17.1 A precision of 15 % relative is found for specimens in
magnitude of the difference will depend upon the proportions of different
the 0.1 to 0.3 % ash range.
inorganic salts present, but based on the following conversion factors for
17.2 No statement of bias can be made as no suitable
the salts commonly present, will generally be about twice the regular ash:
reference material exists for determining bias.
MgSO CaSO MgSO
4 4 4
5 2.99; 5 2.43; 5 1.43 (2)
MgO CaO MgCO
TEST METHOD C—ASHING CELLULOSE BY
CaSO Na SO
4 2 4
SCHONIGER OXIDATION
5 1.36; 5 1.34 (3)
CaSO Na CO
3 2 2
18. Apparatus
13.2 Selection of the specimen shall be in such a manner as
to be representative of the lot being tested (see Note 4).
18.1 Combustion Flasks, 5000 mL, round bottom, borosili-
cate glass, with 65/40 ball and joint stopper. The flasks are
14. Procedure
equipped with perforated platinum specimen carriers sealed
14.1 Weigh out to the nearest 0.05 g sufficient cellulose to into the extended stem of the flask stopper.
give the correct range of ash weight (see Table 1). At the same 18.2 Igniter, suitable for igniting the specimen in the flask.
time, weigh a separate specimen (3 to 5 g) and dry to constant An infrared igniter is preferred.
weight at 1056 2°C for
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