ASTM D3516-89(2011)
(Test Method)Standard Test Methods for Ashing Cellulose
Standard Test Methods for Ashing Cellulose
SIGNIFICANCE AND USE
Ash content gives an estimation of the inorganic content of cellulose samples. The presence of high levels of ash can be expected to be detrimental to the process of making cellulose derivatives. It also provides a rough estimate of silica content which can have a significant effect on the performance of filters in cellulose derivative manufacturing facilities.
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.
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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: D3516 − 89 (Reapproved 2011)
Standard Test Methods for
Ashing Cellulose
This standard is issued under the fixed designation D3516; 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 and it should not be considered as a standard preparative
procedure for elemental analysis.
1.1 These test methods cover four ashing methods for
cellulose. These are intended for use on unbleached and
NOTE 1—The ash content at this ignition temperature is a reasonable
bleached cellulose in sheeted or bulk fiber form. Each one of
measure of the mineral salts and inorganic foreign matter in the cellulose.
the test methods has advantages, so that preference applica- The weight of ash obtained varies with the temperature of ignition. Higher
temperatures(850°C)willconvertcalciumcarbonateandothercarbonates
tions exist for all four.
to the oxides and thus give lower values for ash. The composition of ash
1.2 The test methods appear as follows:
may vary with the pulping process employed for manufacture, which
limits the significance of the ash determination in absolute terms.
Sections
Test Method A—Ash in Cellulose at 575°C 6 to 11
3.2 Test Method B, Sulfated Ash in Cellulose at 575°C—In
Test Method B—Sulfated Ash in Cellulose at 575°C 12 to 17
Test Method C—Ashing Cellulose by Schoniger Oxidation 18 to 22
this ashing procedure the metal salts are converted to sulfates
Test Method D—Wet Ashing of Cellulose for Inorganics 23 to 29
by treatment with sulfuric acid and ignition at 575 6 25°C to
1.3 The values stated in SI units are to be regarded as the
overcome limitations of Test Method A. It should not be
standard. The values given in parentheses are for information
considered as a standard preparative test method for elemental
only.
analysis.
1.4 This standard does not purport to address all of the
NOTE 2—Conventional dry ashing at high temperature (over 850°C)
safety concerns, if any, associated with its use. It is the
results in loss of carbon dioxide from metal carbonates, decomposition of
responsibility of the user of this standard to establish appro-
magnesiumsulfate,andlossofsodiumsalts.Ashingatlowertemperatures
priate safety and health practices and determine the applica-
(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
bility of regulatory limitations prior to use. For a specific
by the burning pulp can raise the temperature far above 575°C for a short
hazard statement, see 20.6.1.
period of time, converting calcium carbonate to the oxide in varying
amounts. The sulfated ash method overcomes these objectionable features
2. Referenced Documents
and has additional advantages. It is relatively insensitive to ignition time.
Ash weight remains constant during weighing, and because the ash does
2.1 ASTM Standards:
not melt it will not attack the crucible.
D1193 Specification for Reagent Water
D1348 Test Methods for Moisture in Cellulose 3.3 Test Method C, Ashing Cellulose by Schoniger
Oxidation—This test method is generally applicable to ashing
3. Summary of Test Methods
cellulose for subsequent analysis of inorganic constituents.The
procedure utilizes the Schoniger technique in which the cellu-
3.1 Test Method A, Ash in Cellulose at 575°C—This test
lose is burned in a combustion flask and all combustion
method measures the ash content of cellulose, which is defined
products are dissolved in an aqueous medium, thus avoiding
for this test as the residue remaining after ignition at 575 6
the possibility of physical loss of sample such as can occur in
25°C until all carbon has been burned off. It is the simplest of
dry ashing (Test Methods A and B). A limitation is the
the four test methods for the determination of ash content only,
relatively small sample of 1 g, which can be ashed without
excessively large apparatus in which to carry out the oxidation
step. Small specimens may not be adequately representative
These test methods are under the jurisdiction of ASTM Committee D01 on
where a particulate contaminate is involved.
Paint and Related Coatings, Materials, and Applications and are the direct
responsibility of Subcommittee D01.36 on Cellulose and Cellulose Derivatives.
3.4 Test Method D, Wet Ashing of Cellulose for Inorganics—
Current edition approved June 1, 2011. Published June 2011. Originally
This test method is recommended for ashing cellulose for
approved in 1976. Last previous edition approved in 2006 as D3516 – 89 (2006).
DOI: 10.1520/D3516-89R11.
subsequent analysis of inorganic constituents. The procedure
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
employs saturation of the cellulose with a concentrated solu-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tion of hydrogen peroxide followed by incremental addition to
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. a small volume of concentrated sulfuric acid. It has the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3516 − 89 (2011)
advantage over Test Method C of not requiring special appa- 7. Test Specimen
ratus and can be readily applied to samples of 5 to 10 g. The
7.1 The amount of cellulose selected for each ash determi-
test method becomes tedious and less convenient for use where
nation depends on the ash content of the test specimen and
larger specimens such as 50 or 100 g are required. Specimens
should be varied so that the weight of the ash will be not less
this large, although not generally required, may be necessary
than10mgandpreferablyover20mg.Table1givessuggested
for the determination of trace levels of constituents such as
sample sizes.
manganese or silica. Smaller samples may not be adequately
7.2 Selection of the specimen shall be in such a manner as
representative where a particulate contaminate is 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
whichcanhaveasignificanteffectontheperformanceoffilters
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 D1348, Method B is suitable. However,
accuracy of the moisture test is not critical for the ash determination and
Unless otherwise indicated, it is intended that all reagents shall
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
8.2 Heat the platinum dish in the muffle furnace at 575°C
specifications are available. Other grades may be used, pro-
for 15 min, cool and weigh to the nearest 0.1 mg. Place the
vided it is first ascertained that the reagent is of sufficiently
weighed cellulose in the platinum dish and place the dish on
high purity to permit its use without lessening the accuracy of
the open door of the muffle furnace, previously set and allowed
the determination.
to reach equilibrium at 575°C. Allow the cellulose to char
5.2 Purity of Water—Unless otherwise indicated, references
without flame by gradually moving the dish into the muffle,
to water shall be understood to mean reagent water as defined
and continue ashing with the door closed for 1 h.
in Specification D1193.
NOTE 6—With some pulps, the character of the ash inhibits complete
TEST METHOD A—ASH IN CELLULOSE AT 575°C
carbon removal and gray or black specks persist after3hof ignition. The
addition of a few drops of distilled water to the ash after 8.3 followed by
6. Apparatus drying and reignition at 575°C for1hor more may be required. Extreme
cases may require a second treatment with water.
6.1 Balance, with an accuracy to 0.05 g is required for
NOTE 7—If the sample is too large, either separate ashings are required
weighing cellulose samples.
or successive additions of cellulose are made with extreme care so as not
to disturb the ash. 8.2 is then repeated between each addition.
6.2 Analytical Balance, with a sensitivity of 0.1 mg is
8.3 Remove the dish from the muffle furnace and allow to
required. It should be checked with Class S weights.
cool somewhat. Place it in the desiccator and allow it to cool to
6.3 Drying Oven, with the capability of maintaining a
room temperature.
temperature of 105 6 2°C.
NOTE 8—Care must be taken at all times to keep drafts away from the
6.4 Desiccator, such as silica gel, indicating drierite, or
light, fluffy ash.
magnesium perchlorate are suitable.
8.4 Weigh the dish and ash to the nearest 0.1 mg. Reignite
6.5 Muffle Furnace, electric, capable of maintaining a tem-
for a 15-min period and reweigh. Repeat as required to obtain
perature of 575 6 25°C, is recommended.
constant weight.
NOTE 3—Back to front temperatures in muffle furnaces frequently
9. Calculation
exceed the 625°C range, so that operating limits should be established for
a given furnace.
9.1 Calculate the ash percent of moisture-free cellulose, E,
6.6 Dish, platinum, 100-mL capacity or larger. Porcelain
as follows:
crucibles are not recommended.
6.7 Tongs, approximately 0.5 m (20 in.) long, with nickel-
TABLE 1 Suggested Sample Sizes
chromium or platinum tips.
Ash, % Moisture-Free Cellulose, g
Over 0.5 5
Reagent Chemicals, American Chemical Society Specifications, American
0.20 to 0.5 10
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
0.12 to 0.2 20
listed by the American Chemical Society, see Analar Standards for Laboratory
0.08 to 0.12 30
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
0.04 to 0.08 40
and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, Less than 0.04 50
MD.
D3516 − 89 (2011)
C 2 B 100 100 14.4 Moisten the ash with 1 to 2 mLof concentrated H SO
~ !~ !~ !
2 4
E 5 (1)
~A!~D! and heat on a hot plate until all the dense white fumes of sulfur
trioxide (SO ) are liberated.
where:
14.5 Place in the muffle furnace and ignite at 575°C for 1 h.
A = weight of specimen as is, g,
If carbon persists repeat 14.3, 14.4, and 14.5.
B = weight of dish, g,
C = weight of dish plus ash, g, and
14.6 After the last trace of carbon has disappeared, ignite in
D = oven dry cellulose in specimen, %
the muffle furnace for1hat 575°C.
14.7 Remove the dish and allow it to cool somewhat before
10. Report
placing it in desiccator and cooling to room temperature.
10.1 Report the results to the nearest 0.01 %. Duplicate
14.8 Weigh the dish and sulfated ash to the nearest 0.1 mg.
determinations should check within approximately 5 %.
Reignite for a 15-min period and reweigh. Repeat as required
to obtain constant weight.
11. Precision and Bias
NOTE 10—To remove the ash from the dish, clean with boiling
11.1 Aprecisionof8 %relativeatthe95 %confidencelevel
hydrochloric acid.
is found for specimens at the 0.05 % ash level.
NOTE 11—On igniting sulfated ash at 575°C, there should be no fusion
with the dishes, even when ashing cellulose that gives an alkaline ash.
11.2 No statement of bias can be made as no suitable
reference material exists for determining bias.
14.9 Prepare a reagent blank for the H SO corresponding
2 4
to the number of millilitres of H SO used in 14.4 and 14.5,by
2 4
TEST METHOD B—SULFATED ASH IN
the addition of the acid to a platinum dish after ignition and
CELLULOSE AT 575°C
true weight was determined, and carrying through 14.4-14.8 as
they apply.
12. Apparatus and Reagent
12.1 Hot Plate.
15. Calculation
12.2 Additional apparatus shall be in accordance with Sec-
15.1 Calculate the sulfated ash, S, as percent of moisture-
tion 6.
free cellulose, as follows:
12.3 Sulfuric Acid—Concentrated H SO .
C 2 B 2 R 100 100
~ !~ !~ !
2 4
S 5 (4)
~A!~D!
13. Test Specimen
where:
13.1 The amount of cellulose selected for each ash deter-
A = weight of specimen, g,
mination depends upon the sulfated ash content of the test
B = weight of dish, g,
specimen and should be varied so that the weight of the ash
C = weight of dish plus sulfated ash, g,
will be not less than 10 mg and preferably over 20 mg. Table
R = weight of H SO reagent blank residue, g, and
2 4
1 gives suggested specimen sizes for Test MethodA. The table
D = oven-dry cellulose in specimen, %.
is applicable to sulfated ash also, providing the percent ash
column is taken as percent sulfated ash.
16. Report
NOTE 9—The sulfated ash values will be higher than the ash obtained 16.1 Report the results to the nearest 0.01 %. Duplicate
by ignition of the cellulose without addition of the sulfuric acid. The
determinations should check within approximately 5 %.
magnitude of the difference will depend upon the proportions of different
inorganic salts present, but based on the following conversion factors for
17. Precision and Bias
the salts commonly present, will generally be about twice the regular ash:
17.1 A precision of 15 % relative is found for specimens in
MgSO CaSO MgSO
4 4 4
5 2.99; 5 2.43; 5 1.43 (2)
the 0.1 to 0.3 % ash range.
MgO CaO MgCO
17.2 No statement of bias can be made as no suitable
CaSO Na SO
4 2 4
5 1.36; 5 1.34 (3)
reference material exists for determining bias.
CaSO Na CO
3 2 2
13.2 Selection of the specimen shall be in such a manner as
TEST METHOD C—ASHING CELLULOSE BY
to be representative of the lot being tested (see Note 4).
SCHONIGER OXIDATION
14. Procedure 18. Apparatus
14.1 Weigh out to the nearest 0.05 g sufficient cellulose to 18.1 Combustion Flasks, 5000 mL, round bottom, borosili-
give the correct range of ash weight (see Table 1).At the same cate glass, with 65/40 ball and joint stopper. The flasks are
time, weigh a separate specimen (3 to 5 g) and dry to constant equipped with perforated platinum specimen carriers sealed
weightat105 62
...
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