ASTM D3516-89(2000)

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An American National Standard
Designation:D3516–89(Reapproved 2000)
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.
NOTE 1—The ash content at this ignition temperature is a reasonable
1. Scope
measure of the mineral salts and inorganic foreign matter in the cellulose.
1.1 These test methods cover four ashing methods for
The weight of ash obtained varies with the temperature of ignition. Higher
cellulose. These are intended for use on unbleached and
temperatures(850°C)willconvertcalciumcarbonateandothercarbonates
bleached cellulose in sheeted or bulk fiber form. Each one of
to the oxides and thus give lower values for ash. The composition of ash
the test methods has advantages, so that preference applica- may vary with the pulping process employed for manufacture, which
limits the significance of the ash determination in absolute terms.
tions exist for all four.
1.2 The test methods appear as follows:
3.2 Test Method B, Sulfated Ash in Cellulose at 575°C—In
Sections
this ashing procedure the metal salts are converted to sulfates
6to11
by treatment with sulfuric acid and ignition at 575 6 25°C to
Test Method A—Ash in Cellulose at 575°C
overcome limitations of Test Method A. It should not be
Test Method B—Sulfated Ash in Cellulose at 575°C 12 to 17
Test Method C—Ashing Cellulose by Schoniger Oxidation 18 to 22
considered as a standard preparative test method for elemental
Test Method D—WetAshing of Cellulose for Inorganics 23 to 29
analysis.
1.3 The values stated in SI units are to be regarded as the
NOTE 2—Conventional dry ashing at high temperature (over 850°C)
standard. The values given in parentheses are for information
results in loss of carbon dioxide from metal carbonates, decomposition of
only.
magnesiumsulfate,andlossofsodiumsalts.Ashingatlowertemperatures
1.4 This standard does not purport to address all of the
(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
safety concerns, if any, associated with its use. It is the
by the burning pulp can raise the temperature far above 575°C for a short
responsibility of the user of this standard to establish appro-
period of time, converting calcium carbonate to the oxide in varying
priate safety and health practices and determine the applica-
amounts. The sulfated ash method overcomes these objectionable features
bility of regulatory limitations prior to use. For a specific
and has additional advantages. It is relatively insensitive to ignition time.
hazard statement, see 20.6.1.
Ash weight remains constant during weighing, and because the ash does
not melt it will not attack the crucible.
2. Referenced Documents
3.3 Test Method C, Ashing Cellulose by Schoniger
2.1 ASTM Standards:
Oxidation—This test method is generally applicable to ashing
D 1193 Specification for Reagent Water
cellulose for subsequent analysis of inorganic constituents.The
D 1348 Test Methods for Moisture in Cellulose
procedure utilizes the Schoniger technique in which the cellu-
lose is burned in a combustion flask and all combustion
3. Summary of Test Methods
products are dissolved in an aqueous medium, thus avoiding
3.1 Test Method A, Ash in Cellulose at 575°C—This test
the possibility of physical loss of sample such as can occur in
method measures the ash content of cellulose, which is defined
dry ashing (Test Methods A and B). A limitation is the
for this test as the residue remaining after ignition at 575 6
relatively small sample of 1 g, which can be ashed without
25°C until all carbon has been burned off. It is the simplest of
excessively large apparatus in which to carry out the oxidation
the four test methods for the determination of ash content only,
step. Small specimens may not be adequately representative
and it should not be considered as a standard preparative
where a particulate contaminate is involved.
procedure for elemental analysis.
3.4 Test Method D, Wet Ashing of Cellulose for
Inorganics—This test method is recommended for ashing
cellulose for subsequent analysis of inorganic constituents.The
These test methods are under the jurisdiction of ASTM Committee D01 on
procedure employs saturation of the cellulose with a concen-
Paint and Related Coatings, Materials, and Applications and are the direct
responsibility of Subcommittee D01.36 on Cellulose and Cellulose Derivatives.
trated solution of hydrogen peroxide followed by incremental
Current edition approved Oct. 27, 1989. Published December 1989. Originally
addition to a small volume of concentrated sulfuric acid. It has
published as D 3516 – 76. Last previous edition D 3516 – 76 (1985).
the advantage over Test Method C of not requiring special
Annual Book of ASTM Standards, Vol 11.01.
Annual Book of ASTM Standards, Vol 06.03. apparatus and can be readily applied to samples of 5 to 10 g.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959, United States.
D3516
The test method becomes tedious and less convenient for use should be varied so that the weight of the ash will be not less
where larger specimens such as 50 or 100 g are required. than 10 mgandpreferably over 20 mg.Table 1gives suggested
Specimens this large, although not generally required, may be sample sizes.
necessary for the determination of trace levels of constituents 7.2 Selection of the specimen shall be in such a manner as
such as manganese or silica. Smaller samples may not be to be representative of the lot being tested.
adequately representative where a particulate contaminate is
NOTE 4—No set sampling procedure has been established to be
involved.
applicable to all samples. It will suffice to specify that the specimen shall
be representative of the lot being sampled.
4. Significance and Use
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
8.1 Weigh out, to the nearest 0.05 g, sufficient cellulose to
expected to be detrimental to the process of making cellulose
give the correct range of ash weight (see Table 1).At the same
derivatives. It also provides a rough estimate of silica content
time, a separate specimen (3 to 5 g) should be weighed and
whichcanhaveasignificanteffectontheperformanceoffilters
dried at 105°C for a moisture determination.
in cellulose derivative manufacturing facilities.
NOTE 5—Test Methods D 1348, Method B is suitable. However,
accuracy of the moisture test is not critical for the ash determination and
5. Purity of Reagents
any method capable of obtaining the percent oven dry within 0.5 % of the
5.1 Reagent grade chemicals shall be used in all tests.
true value is adequate.
Unless otherwise indicated, it is intended that all reagents shall
8.2 Heat the platinum dish in the muffle furnace at 575°C
conform to the specifications of the Committee on Analytical
for 15 min, cool and weigh to the nearest 0.1 mg. Place the
Reagents of the American Chemical Society, where such
weighed cellulose in the platinum dish and place the dish on
specifications are available. Other grades may be used, pro-
the open door of the muffle furnace, previously set and allowed
vided it is first ascertained that the reagent is of sufficiently
to reach equilibrium at 575°C. Allow the cellulose to char
high purity to permit its use without lessening the accuracy of
without flame by gradually moving the dish into the muffle,
the determination.
and continue ashing with the door closed for 1 h.
5.2 Purity of Water—Unless otherwise indicated, references
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 D 1193. 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
or successive additions of cellulose are made with extreme care so as not
6.1 Balance, with an accuracy to 0.05 g is required for
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.
~C 2 B!~100!~100!
6.7 Tongs, approximately 0.5 m (20 in.) long, with nickel-
E 5 (1)
~A! ~D!
chromium or platinum tips.
7. Test Specimen
7.1 The amount of cellulose selected for each ash determi-
TABLE 1 Suggested Sample Sizes
nation depends on the ash content of the test specimen and
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
14.6 After the last trace of carbon has disappeared, ignite in
where:
the muffle furnace for1hat 575°C.
A = weight of specimen as is, g,
14.7 Remove the dish and allow it to cool somewhat before
B = weight of dish, g,
C = weight of dish plus ash, g, and placing it in desiccator and cooling to room temperature.
D = 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 Aprecisionof8 %relativeatthe95 %confidencelevel
14.9 Prepare a reagent blank for the H SO corresponding
2 4
is found for specimens at the 0.05 % ash level.
tothenumberofmillilitresofH SO usedin14.4and14.5,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
12. Apparatus and Reagent
15.1 Calculate the sulfated ash, S, as percent of moisture-
free cellulose, as follows:
12.1 Hot Plate.
12.2 Additional apparatus shall be in accordance with Sec-
C 2 B 2 R! 100! 100!
~ ~ ~
S 5 (4)
tion 6.
~A! ~D!
12.3 Sulfuric Acid—Concentrated H SO .
2 4
where:
13. Test Specimen A = weight of specimen, g,
B = weight of dish, g,
13.1 The amount of cellulose selected for each ash deter-
C = weight of dish plus sulfated ash, g,
mination depends upon the sulfated ash content of the test
R = weight of H SO reagent blank residue, g, and
2 4
specimen and should be varied so that the weight of the ash
D = oven-dry cellulose in specimen, %.
will be not less than 10 mg and preferably over 20 mg. Table
1 gives suggested specimen sizes for Test MethodA. The table
16. Report
is applicable to sulfated ash also, providing the percent ash
16.1 Report the results to the nearest 0.01 %. Duplicate
column is taken as percent sulfated ash.
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 17. Precision and Bias
magnitude of the difference will depend upon the proportions of different
17.1 A precision of 15 % relative is found for specimens in
inorganic salts present, but based on the following conversion factors for
the 0.1 to 0.3 % ash range.
the salts commonly present, will generally be about twice the regular ash:
17.2 No statement of bias can be made as no suitable
MgSO CaSO MgSO
4 4 4
reference material exists for determining bias.
5 2.99; 5 2.43; 5 1.43 (2)
MgO CaO MgCO
TEST METHOD C—ASHING CELLULOSE BY
CaSO Na SO
SCHONIGER OXIDATION
4 2 4
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
18.1 Combustion Flasks, 5000 mL, round bottom, borosili-
to be representative of the lot being tested (see Note 4).
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 a moisture determination (see Note 5). 18.3 Specimen Wrappers, black paper.
14.2 See 8.2. 18.4 Pipet, 5 mL.
14.3 Remove the dish and allow it to cool to room tempera- 18.5 Volumetric Flask,50mL.
ture (see Note 7 and Note 8).
19. Reagents
14.4 Moisten the ash with 1 to 2 mLof concentrated H SO
2 4
and heat on a hot p
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