ASTM D3516-89(2006)
(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.
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.
General Information
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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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(Reapproved2006)
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 weight of ash obtained varies with the temperature of ignition. Higher
the test methods has advantages, so that preference applica-
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
Sections
limits the significance of the ash determination in absolute terms.
6 to 11
Test Method A—Ash in Cellulose at 575°C
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
this ashing procedure the metal salts are converted to sulfates
Test Method C—Ashing Cellulose by Schoniger Oxidation 18 to 22
by treatment with sulfuric acid and ignition at 575 6 25°C to
Test Method D—Wet Ashing of Cellulose for Inorganics 23 to 29
overcome limitations of Test Method A. It should not be
1.3 The values stated in SI units are to be regarded as the
considered as a standard preparative test method for elemental
standard. The values given in parentheses are for information
analysis.
only.
1.4 This standard does not purport to address all of the NOTE 2—Conventional dry ashing at high temperature (over 850°C)
results in loss of carbon dioxide from metal carbonates, decomposition of
safety concerns, if any, associated with its use. It is the
magnesiumsulfate,andlossofsodiumsalts.Ashingatlowertemperatures
responsibility of the user of this standard to establish appro-
(575°C) gives a better estimate of the inorganic impurities, but has the
priate safety and health practices and determine the applica-
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
celluloseforsubsequentanalysisofinorganicconstituents.The
3.1 Test Method A, Ash in Cellulose at 575°C—This test
procedure utilizes the Schoniger technique in which the cellu-
method measures the ash content of cellulose, which is defined lose is burned in a combustion flask and all combustion
for this test as the residue remaining after ignition at 575 6
products are dissolved in an aqueous medium, thus avoiding
25°C until all carbon has been burned off. It is the simplest of the possibility of physical loss of sample such as can occur in
the four test methods for the determination of ash content only,
dry ashing (Test Methods A and B). A limitation is the
relatively small sample of 1 g, which can be ashed without
excessively large apparatus in which to carry out the oxidation
These test methods are under the jurisdiction of ASTM Committee D01 on step. Small specimens may not be adequately representative
Paint and Related Coatings, Materials, and Applications and are the direct
where a particulate contaminate is involved.
responsibility of Subcommittee D01.36 on Cellulose and Cellulose Derivatives.
3.4 Test Method D, Wet Ashing of Cellulose for
Current edition approved April 1, 2006. Published April 2006. Originally
Inorganics—This test method is recommended for ashing
approved in 1976. Last previous edition approved in 2000 as D3516 – 89 (2000).
DOI: 10.1520/D3516-89R06.
celluloseforsubsequentanalysisofinorganicconstituents.The
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
procedure employs saturation of the cellulose with a concen-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
trated solution of hydrogen peroxide followed by incremental
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. addition to a small volume of concentrated sulfuric acid. It has
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D3516–89 (2006)
the advantage over Test Method C of not requiring special 7. Test Specimen
apparatus and can be readily applied to samples of 5 to 10 g.
7.1 The amount of cellulose selected for each ash determi-
The test method becomes tedious and less convenient for use
nation depends on the ash content of the test specimen and
where larger specimens such as 50 or 100 g are required.
should be varied so that the weight of the ash will be not less
Specimens this large, although not generally required, may be
than10mgandpreferablyover20mg.Table1givessuggested
necessary for the determination of trace levels of constituents
sample sizes.
such as manganese or silica. Smaller samples may not be
7.2 Selection of the specimen shall be in such a manner as
adequately representative where a particulate contaminate is
to be representative of the lot being tested.
involved.
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. Significance and Use
be representative of the lot being sampled.
4.1 Ash content gives an estimation of the inorganic content
8. Procedure
of cellulose samples. The presence of high levels of ash can be
expected to be detrimental to the process of making cellulose
8.1 Weigh out, to the nearest 0.05 g, sufficient cellulose to
derivatives. It also provides a rough estimate of silica content
give the correct range of ash weight (see Table 1).At the same
whichcanhaveasignificanteffectontheperformanceoffilters
time, a separate specimen (3 to 5 g) should be weighed and
in cellulose derivative manufacturing facilities.
dried at 105°C for a moisture determination.
NOTE 5—Test Methods D1348, Method B is suitable. However, accu-
5. Purity of Reagents
racy of the moisture test is not critical for the ash determination and any
5.1 Reagent grade chemicals shall be used in all tests.
method capable of obtaining the percent oven dry within 0.5 % of the true
Unless otherwise indicated, it is intended that all reagents shall
value is adequate.
conform to the specifications of the Committee on Analytical
8.2 Heat the platinum dish in the muffle furnace at 575°C
Reagents of the American Chemical Society, where such
for 15 min, cool and weigh to the nearest 0.1 mg. Place the
specifications are available. Other grades may be used, pro-
weighed cellulose in the platinum dish and place the dish on
vided it is first ascertained that the reagent is of sufficiently
the open door of the muffle furnace, previously set and allowed
high purity to permit its use without lessening the accuracy of
to reach equilibrium at 575°C. Allow the cellulose to char
the determination.
without flame by gradually moving the dish into the muffle,
5.2 Purity of Water—Unless otherwise indicated, references
and continue ashing with the door closed for 1 h.
to water shall be understood to mean reagent water as defined
NOTE 6—With some pulps, the character of the ash inhibits complete
in Specification D1193.
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
TEST METHOD A—ASH IN CELLULOSE AT 575°C
drying and reignition at 575°C for1hor more may be required. Extreme
cases may require a second treatment with water.
6. Apparatus
NOTE 7—If the sample is too large, either separate ashings are required
6.1 Balance, with an accuracy to 0.05 g is required for 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.
weighing cellulose samples.
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
exceed the6 25°C range, so that operating limits should be established for
9. Calculation
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-
chromium or platinum tips.
TABLE 1 Suggested Sample Sizes
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 (2006)
~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.
14.5 Place in the muffle furnace and ignite at 575°C for 1 h.
where:
If carbon persists repeat 14.3, 14.4, and 14.5.
A = weight of specimen as is, g,
14.6 After the last trace of carbon has disappeared, ignite in
B = weight of dish, g,
the muffle furnace for1hat 575°C.
C = weight of dish plus ash, g, and
14.7 Remove the dish and allow it to cool somewhat before
D = oven dry cellulose in specimen, %
placing it in desiccator and cooling to room temperature.
14.8 Weigh the dish and sulfated ash to the nearest 0.1 mg.
10. Report
Reignite for a 15-min period and reweigh. Repeat as required
10.1 Report the results to the nearest 0.01 %. Duplicate
to obtain constant weight.
determinations should check within approximately 5 %.
NOTE 10—To remove the ash from the dish, clean with boiling
hydrochloric acid.
11. Precision and Bias
NOTE 11—On igniting sulfated ash at 575°C, there should be no fusion
11.1 Aprecisionof8 %relativeatthe95 %confidencelevel
with the dishes, even when ashing cellulose that gives an alkaline ash.
is found for specimens at the 0.05 % ash level.
14.9 Prepare a reagent blank for the H SO corresponding
2 4
11.2 No statement of bias can be made as no suitable
to the number of millilitres of H SO used in 14.4 and 14.5,by
2 4
reference material exists for determining bias.
the addition of the acid to a platinum dish after ignition and
true weight was determined, and carrying through 14.4-14.8 as
TEST METHOD B—SULFATED ASH IN
they apply.
CELLULOSE AT 575°C
15. Calculation
12. Apparatus and Reagent
15.1 Calculate the sulfated ash, S, as percent of moisture-
12.1 Hot Plate.
free cellulose, as follows:
12.2 Additional apparatus shall be in accordance with Sec-
~C 2 B 2 R!~100!~100!
tion 6.
S 5 (4)
~A! ~D!
12.3 Sulfuric Acid—Concentrated H SO .
2 4
where:
13. Test Specimen
A = weight of specimen, g,
13.1 The amount of cellulose selected for each ash deter-
B = weight of dish, g,
mination depends upon the sulfated ash content of the test
C = weight of dish plus sulfated ash, g,
specimen and should be varied so that the weight of the ash R = weight of H SO reagent blank residue, g, and
2 4
will be not less than 10 mg and preferably over 20 mg. Table D = oven-dry cellulose in specimen, %.
1 gives suggested specimen sizes for Test MethodA. The table
is applicable to sulfated ash also, providing the percent ash 16. Report
column is taken as percent sulfated ash.
16.1 Report the results to the nearest 0.01 %. Duplicate
determinations should check within approximately 5 %.
NOTE 9—The sulfated ash values will be higher than the ash obtained
by ignition of the cellulose without addition of the sulfuric acid. The
magnitude of the difference will depend upon the proportions of different 17. Precision and Bias
inorganic salts present, but based on the following conversion factors for
17.1 A precision of 15 % relative is found for specimens in
the salts commonly present, will generally be about twice the regular ash:
the 0.1 to 0.3 % ash range.
MgSO CaSO MgSO
4 4 4
17.2 No statement of bias can be made as no suitable
5 2.99; 5 2.43; 5 1.43 (2)
MgO CaO MgCO
reference material exists for determining bias.
CaSO Na SO
4 2 4
TEST METHOD C—ASHING CELLULOSE BY
5 1.36; 5 1.34 (3)
CaSO Na CO
3 2 2
SCHONIGER OXIDATION
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. Apparatus
18.1 Combustion Flasks, 5000 mL, round bottom, borosili-
14. Procedure
cate glass, with 65/40 ball and joint stopper. The flasks are
14.1 Weigh out to the nearest 0.05 g sufficient cellulose to equipped with perforated platinum specimen carriers sealed
give the correct range of ash weight (see Table 1).At the same into the extended stem of the flask stopper.
time, weigh a separate specimen (3 to 5 g) and dry to constant 1
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