ASTM D1857/D1857M-04(2010)
(Test Method)Standard Test Method for Fusibility of Coal and Coke Ash
Standard Test Method for Fusibility of Coal and Coke Ash
SIGNIFICANCE AND USE
Design of most coal combustion and coal conversion equipment anticipates that the ash either remain solid or assume some degree of fluidity, depending on the particular design. Ash fusibility temperatures predict whether the ash will perform properly in the process for which the coal was chosen.
SCOPE
1.1 This test method covers the observation of the temperatures at which triangular pyramids (cones) prepared from coal and coke ash attain and pass through certain defined stages of fusing and flow when heated at a specified rate in controlled, mildly reducing, and where desired, oxidizing atmospheres.
1.2 The test method is empirical, and strict observance of the requirements and conditions is necessary to obtain reproducible temperatures and enable different laboratories to obtain concordant results.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
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.
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Designation: D1857/D1857M − 04(Reapproved 2010)
Standard Test Method for
Fusibility of Coal and Coke Ash
This standard is issued under the fixed designation D1857/D1857M; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 3.1.2 fluid temperature, FT—the temperature at which the
fused mass has spread out in a nearly flat layer with a
1.1 This test method covers the observation of the tempera-
maximum height of 1.6 mm [ ⁄16 in.] as shown by the fifth
tures at which triangular pyramids (cones) prepared from coal
cone, FT, in Fig. 1.
and coke ash attain and pass through certain defined stages of
3.1.3 hemispherical temperature, HT—the temperature at
fusing and flow when heated at a specified rate in controlled,
which the cone has fused down to a hemispherical lump at
mildly reducing, and where desired, oxidizing atmospheres.
which point the height is one half the width of the base as
1.2 The test method is empirical, and strict observance of
shown by the fourth cone, HT, in Fig. 1.
the requirements and conditions is necessary to obtain repro-
3.1.4 initial deformation temperature, IT—the temperature
ducible temperatures and enable different laboratories to obtain
at which the first rounding of the apex of the cone occurs.
concordant results.
Shrinkage or warping of the cone ignored if the tip remains
1.3 The values stated in either SI units or inch-pound units
sharp. In Fig. 1, the first cone shown is an unheated one; the
are to be regarded separately as standard. The values stated in
secondconeITisatypicalconeattheinitialdeformationstage.
each system may not be exact equivalents; therefore, each
3.1.5 softening temperature, ST—the temperature at which
system shall be used independently of the other. Combining
the cone has fused down to a spherical lump in which the
values from the two systems may result in non-conformance
height is equal to the width at the base as shown by the third
with the standard.
cone, ST, in Fig. 1.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 Design of most coal combustion and coal conversion
priate safety and health practices and determine the applica-
equipment anticipates that the ash either remain solid or
bility of regulatory limitations prior to use.
assume some degree of fluidity, depending on the particular
design.Ash fusibility temperatures predict whether the ash will
2. Referenced Documents
perform properly in the process for which the coal was chosen.
2.1 ASTM Standards:
D2013 Practice for Preparing Coal Samples for Analysis
5. Apparatus and Materials
D3174 Test Method for Ash in the Analysis Sample of Coal
5.1 Furnace—Any gas-fired or electric furnace conforming
and Coke from Coal
to the following requirements may be used:
5.1.1 Capable of maintaining a uniform temperature zone in
3. Terminology
which to heat the ash cones. This zone shall be such that the
3.1 Definitions of Terms Specific to This Standard: 1
difference in the melting point of 12.7-mm [ ⁄2-in.] pieces of
3.1.1 The critical temperature points to be observed are as
pure gold wire when mounted in place of the ash cones on the
follows, denoting the atmosphere used:
cone support shall be not greater than 11°C [20°F] in a
reducing atmosphere test run.
5.1.2 Capable of maintaining the desired atmosphere sur-
This test method is under the jurisdiction of ASTM Committee D05 on Coal
rounding the cones during heating. The composition of the
and Coke and is the direct responsibility of D05.21 on Methods of Analysis.
atmosphere, reducing or oxidizing, shall be maintained within
Current edition approved Sept. 1, 2010. Published November 2010. Originally
the limits specified in Section 6. The desired atmosphere in the
approved 1961. Last previous edition approved 2004 as D1857 – 04. DOI: 10.1520/
D1857-04R10.
gas-fired furnace surrounding the cones shall be obtained by
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
regulation of the ratio of gas to air in the combustion mixture.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
The desired atmosphere in the electric furnace shall be ob-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tained by means of gases introduced into the heating chamber.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1857/D1857M − 04 (2010)
(Fig. 1) has been passed, and then sighted on the cone support.
The pyrometer shall have readable graduations not larger than
5.5°C [10°F].
NOTE 1—The pyrometer equipment shall be standardized periodically
by a suitably equipped standardizing laboratory such as that of the
National Bureau of Standards, or checked periodically against equipment
FIG. 1 Critical Temperature Points
certified by the Bureau of Standards.
5.3.2 Thermocouple—A thermocouple of platinum and
platinum-rhodium, protected from the furnace gases by a
The muffle shall be gas impervious, free from cracks, and the
glazed porcelain sheath, shall be used with a high-resistance
closure plug tight-fitting.The gas supply tube shall be sealed to
millivoltmeterorpotentiometeraccurateandreadabletowithin
the back wall of the preheating chamber and shall not extend to
5.5°C [10°F]. The sheath shall be sealed to the furnace wall by
the front of the preheating chamber against the perforated
alundum cement. The hot junction of the thermocouple shall
baffle.
touch the end of the sheath and shall be located in the center of
5.1.3 Capable of regulation so that the rate of temperature
the muffle and immediately to the rear of the cones. The
rise shall be 8 6 3°C [15 6 5°F]/min.
thermocouple protective sheath shall be checked periodically
5.1.4 Providingmeansofobservingtheashconesduringthe
for cracks. The thermocouple and its meter shall meet the
heating. Observation on the same horizontal plane as the
requirements of Section 9.The potentiometer or millivoltmeter
cone-support surface shall be possible.
shall be so located or adequately shielded as to prevent radiant
5.2 Cone Mold—A commercially available cone mold as
and convection heating of the cold junction. The room tem-
shown in Fig. 2.The cone shall be 19 mm [ ⁄4 in.] in height and
perature compensator shall be adjusted to the existing tempera-
6.4 mm [ ⁄4 in.] in width at each side of the base which is an
ture.
equilateral triangle. A steel spatula with a pointed tip, ground
5.4 Ash-Cone Refractory Support—The ash cones shall be
off to fit the cone depression in the mold, is suitable for
mounted on a refractory base composed of a mixture of equal
removal of the ash cone.
parts by weight of kaolin and alumina conforming to the
5.3 Optical Pyrometer or Thermocouple, for temperature
following requirements:
measurements, conforming to the following requirements:
5.4.1 Kaolin—NF-grade powder passing a 75-µm (No. 200)
5.3.1 Optical Pyrometer—An optical pyrometer of the dis-
sieve.
appearing filament type shall be used. The instrument shall
5.4.2 Aluminum Oxide—Reagent grade ignited powder
have been calibrated to be accurate within 11°C [20°F] up to
passing a 150-µm (No. 100) sieve.
1400°C[2550°F]andwithin16°C[30°F]from1400to1600°C
5.5 Refractory Support Mold—A mold with flat top and
[2550 to 2900°F] (Note 1). The pyrometer filament shall be
bottom surfaces to provide a refractory support of suitable
sighted on the cones until the softening point temperature C
thickness to minimize warping. A sidemold not over 6.4 mm
[ ⁄4 in.] high of any convenient shape, placed on an iron plate
so that the top surface of the refractory mix can be struck off
flat and parallel to the base by means of a straightedge, is
satisfactory. For electric furnace use, legs not over ⁄8 in. [3
mm] long may be provided on the corners of the cone support
by suitable holes bored in the iron base plate of the mold.
5.6 Gold Wire —0.51-mm diameter (twenty-four gage) or
larger round wire of 99.98 % purity, but drawn from metal of
99.99 % purity, and having a melting point of 1063°C
[1945°F].
5.7 Nickel Wire —0.51-mm diameter (twenty-four gage) or
larger round wire of CP nickel, 99.98 % pure, fully annealed,
and having a melting point of 1452°C [2645°F].
6. Test Atmosphere
6.1 Gas-Fired Furnace:
6.1.1 Reducing Atmosphere Test—A mildly reducing atmo-
Inch-pound
SI Units,
Units,
sphere surrounding the cones shall be maintained during the
mm
in.
⁄4 6.4
⁄4 19.1 Gold wire of this purity can be purchased from the Baker Dental Division of
1 ⁄2 38.1 Engelhard Industries, Inc., 850 PassaicAve., East Newark, NJ 07029 or from Leico
2 50.2 Industries, Inc., 250 W. 57th St., New York, NY 10019.
3 76.2
Nickel wire of this purity can be purchased with the additional specification of
havingaminimumcoefficientofresistancefor0to100°Cof0.006 73Ω/Ω·°C,from
FIG. 2 Brass Cone Mold Leico Industries, Inc., 250 W. 57th St., New York, NY 10019.
D1857/D1857M − 04 (2010)
test in the gas-fired furnace. Hydrogen, hydrocarbons, and expulsion of volatile matter (Note 3). Complete the conversion
carbon monoxide shall be considered as reducing gases; to ash at a temperature of 800 to 900°C [1470 to 1650°F].
oxygen, carbon dioxide, and water vapor shall be considered as Transfer the ash to an agate mortar (Note 4) and grind it so that
oxidizing gases. Nitrogen is inert. The ratio by volume of it will pass a 75-µm (No. 200) sieve. Then spread the ash in a
reducing gases to oxidizing gases in the atmosphere shall be thin layer in a fireclay, silica, or porcelain dish and ignite it in
between the limits of 20 to 80 and 80 to 20, that is, on a a stream of oxygen for 1 ⁄2 h at 800 to 850°C [1470 to 1560°F]
nitrogen-free basis, the total amount of reducing gases present to ensure complete and uniform oxidation of the ash.Any tube
shall be between the limits of 20 and 80 volume %. A flame or muffle-type furnace which, when supplied with an oxygen
152 to 203 mm [6 to 8 in.] in height and tinged with yellow flow of not less than one furnace volume in 5 min, will
above the furnace outlet has been found to provide an maintain a highly oxidizing atmosphere and will be suitable.
atmosphere within the specified limits.
NOTE 3—A heating rate conforming to that used for the ash determi-
6.1.2 Oxidizing Atmosphere Test—An atmosphere contain-
nation specified in Section 7 of Test Method D3174 is satisfactory.
ing a minimum amount of reducing gases shall be maintained
NOTE 4—Amechanical agate mortar grinder will save time where many
determinations are made. An iron mortar or pestle must not be used.
surrounding the cones during the test in the gas-fired furnace.
On a nitrogen-free basis, the volume of reducing gases present
8. Preparation of Cones
in the atmosphere shall not exceed volume 10 %. Combustion
with the maximum possible quantity of air with preservation of
8.1 Thoroughly mix the ignited ash in a mechanical mixer
the specified rate of temperature increase has been found to
or on a sheet of glazed paper or oil cloth by raising first one
provide an atmosphere within the specified limits. A com-
corner to roll the ash over and then raising each of the other
pletely blue flame, not over 50 mm [2 in.] in height above the
corners in rotation in the same manner until each corner has
outlet at the beginning of the test, provides the desired
been raised five times or more.
atmosphere; and, by regulation of the combustion gas-air ratio,
8.2 Take sufficient ash for the number of cones desired from
the specified atmosphere and temperature rise can be main-
various parts of the bulk ash. Moisten the ash with a few drops
tained.
of a clear, filtered (if necessary) 10 % solution of dextrin
6.2 Electric Furnace:
containing 0.1 % salicylic acid as a preservative and work it
6.2.1 ReducingAtmosphere Test—Aregulatedflowofgasof
intoastiffplasticmasswithaspatula.Presstheplasticmaterial
the nominal composition, 60 % carbon monoxide and 40 6 5
firmly with a spatula into the cone mold to form the triangular
volume % carbon dioxide, shall be maintained in the heating
pyramids. Strike off the exposed surfaces of the material
chamber throughout the test (Note 2) in the electric furnace.
smooth and remove the cones from the mold by applying
The gas stream shall be regulated by any convenient means to
pressure at the base with a suitably pointed spatula. Previous
provide a measured flow of 1.3 to 1.5 furnace volumes per
coatingofthemoldwithathinlayerofpetroleumjelly,thinned
minute.
with kerosene (if necessary), aids in preventing adherence of
6.2.2 Oxidizing Atmosphere Test—A regulated stream of air
the cones to the mold and in providing the sharp point and
shall be maintained throughout the test in the electric furnace.
edges desired in the cone. With certain coal ashes, cones with
The gas stream shall be regulated by any convenient means to
sharp points and edges can be obtained using distilled water in
provide a measured flow of 1.3 to 1.5 furnace volumes per
place of the dextrin solution and without the use of petroleum
minute.
jelly.
NOTE 2—Before using new cylinders of CO/CO reducing gas, the
8.3 Place the cones in a suitable location to dry sufficiently
contents should be mixed according to the gas manufacturer’s recommen-
to permit handling without deformation. Mount the dried cone
dations. To assure that the gas remains mixed, the temperature of the
vertically on a freshly prepared refractory base. Moisten a
cylinder contents should be maintained above the critical temperature at
portion of the well-mixed kaolin-alumina mixture with the
which CO can liquify and separate.
minimumamountofwatertomakeaworkable,butstiff,plastic
7. Preparation of Ash mass, and firmly press it into the support mold. Strike off the
surface of the mass flat and smooth with a steel spatula,
7.1 Use coal or coke passing a 250-µm (No. 60) sieve
moistening with one or two drops of water if necessary to
prepared in accordance with Method D2013, to obtain the ash
obtain a smooth surface. A number of cones may be mounted
by incineration in a well-ventilated muffle furnace. The quan-
on one base. Make shallow triangular depressions, not over 0.8
tity of coal or coke required will vary with the ash content;
mm [ ⁄32 in.] in depth, with a triangular file g
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:D1857–04 Designation: D1857/D1857M – 04 (Reapproved 2010)
Standard Test Method for
Fusibility of Coal and Coke Ash
This standard is issued under the fixed designation D1857/D1857M; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope
1.1 This test method covers the observation of the temperatures at which triangular pyramids (cones) prepared from coal and
coke ash attain and pass through certain defined stages of fusing and flow when heated at a specified rate in controlled, mildly
reducing, and where desired, oxidizing atmospheres.
1.2 The test method is empirical, and strict observance of the requirements and conditions is necessary to obtain reproducible
temperatures and enable different laboratories to obtain concordant results.
1.3The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
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.
2. Referenced Documents
2.1 ASTM Standards:
D2013 Practice for Preparing Coal Samples for Analysis
D3174 Test Method for Ash in the Analysis Sample of Coal and Coke from Coal
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 The critical temperature points to be observed are as follows, denoting the atmosphere used:
3.1.2 fluid temperature, FT—the temperature at which the fused mass has spread out in a nearly flat layer with a maximum
height of 1.6 mm ([ ⁄16 in.)in.] as shown by the fifth cone, FT, in Fig. 1.
3.1.3 hemispherical temperature, HT—the temperature at which the cone has fused down to a hemispherical lump at which
point the height is one half the width of the base as shown by the fourth cone, HT, in Fig. 1.
3.1.4 initial deformation temperature, IT—the temperature at which the first rounding of the apex of the cone occurs. Shrinkage
or warping of the cone ignored if the tip remains sharp. In Fig. 1, the first cone shown is an unheated one; the second cone IT is
a typical cone at the initial deformation stage.
3.1.5 softening temperature, ST—the temperature at which the cone has fused down to a spherical lump in which the height is
equal to the width at the base as shown by the third cone, ST, in Fig. 1.
4. Significance and Use
4.1 Design of most coal combustion and coal conversion equipment anticipates that the ash either remain solid or assume some
degree of fluidity, depending on the particular design. Ash fusibility temperatures predict whether the ash will perform properly
in the process for which the coal was chosen.
5. Apparatus and Materials
5.1 Furnace—Any gas-fired or electric furnace conforming to the following requirements may be used:
This test method is under the jurisdiction of ASTM Committee D05 on Coal and Coke and is the direct responsibility of D05.21 on Methods of Analysis.
Current edition approved July 1, 2004. Published July 2004. Originally approved 1961. Last previous edition approved 2003 as D1857–03. DOI: 10.1520/D1857-04.
Current edition approved Sept. 1, 2010. Published November 2010. Originally approved 1961. Last previous edition approved 2004 as D1857 – 04. DOI:
10.1520/D1857-04R10.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D1857/D1857M – 04 (2010)
FIG. 1 Critical Temperature Points
5.1.1 Capable of maintaining a uniform temperature zone in which to heat the ash cones. This zone shall be such that the
difference in the melting point of 12.7-mm ([ ⁄2-in.)-in.] pieces of pure gold wire when mounted in place of the ash cones on the
cone support shall be not greater than 11°C (20°F)[20°F] in a reducing atmosphere test run.
5.1.2 Capable of maintaining the desired atmosphere surrounding the cones during heating.The composition of the atmosphere,
reducing or oxidizing, shall be maintained within the limits specified in Section 6. The desired atmosphere in the gas-fired furnace
surrounding the cones shall be obtained by regulation of the ratio of gas to air in the combustion mixture. The desired atmosphere
intheelectricfurnaceshallbeobtainedbymeansofgasesintroducedintotheheatingchamber.Themuffleshallbegasimpervious,
free from cracks, and the closure plug tight-fitting. The gas supply tube shall be sealed to the back wall of the preheating chamber
and shall not extend to the front of the preheating chamber against the perforated baffle.
5.1.3 Capable of regulation so that the rate of temperature rise shall be 8 6 3°C (15[15 6 5°F)/min. 5°F]/min.
5.1.4 Providing means of observing the ash cones during the heating. Observation on the same horizontal plane as the
cone-support surface shall be possible.
5.2 Cone Mold—A commercially available cone mold as shown in Fig. 2. The cone shall be 19 mm ([ ⁄4 in.)in.] in height and
6.4 mm ([ ⁄4 in.)in.] in width at each side of the base which is an equilateral triangle. A steel spatula with a pointed tip, ground
off to fit the cone depression in the mold, is suitable for removal of the ash cone.
5.3 Optical Pyrometer or Thermocouple, for temperature measurements, conforming to the following requirements:
5.3.1 Optical Pyrometer—An optical pyrometer of the disappearing filament type shall be used.The instrument shall have been
calibrated to be accurate within 11°C (20°F)[20°F] up to 1400°C (2550°F)[2550°F] and within 16°C (30°F)[30°F] from 1400 to
1600°C (2550[2550 to 2900°F)2900°F] (Note 1). The pyrometer filament shall be sighted on the cones until the softening point
temperature C (Fig. 1) has been passed, and then sighted on the cone support. The pyrometer shall have readable graduations not
larger than 5.5°C (10°F).[10°F].
NOTE 1—The pyrometer equipment shall be standardized periodically by a suitably equipped standardizing laboratory such as that of the National
Bureau of Standards, or checked periodically against equipment certified by the Bureau of Standards.
5.3.2 Thermocouple—A thermocouple of platinum and platinum-rhodium, protected from the furnace gases by a glazed
porcelain sheath, shall be used with a high-resistance millivoltmeter or potentiometer accurate and readable to within 5.5°C
(10°F).[10°F].The sheath shall be sealed to the furnace wall by alundum cement.The hot junction of the thermocouple shall touch
Inch-pound
SI Units,
Units,
mm
in.
⁄4 6.4
⁄4 19.1
1 ⁄2 38.1
2 50.2
3 76.2
FIG. 2 Brass Cone Mold
D1857/D1857M – 04 (2010)
the end of the sheath and shall be located in the center of the muffle and immediately to the rear of the cones. The thermocouple
protective sheath shall be checked periodically for cracks. The thermocouple and its meter shall meet the requirements of Section
9. The potentiometer or millivoltmeter shall be so located or adequately shielded as to prevent radiant and convection heating of
the cold junction. The room temperature compensator shall be adjusted to the existing temperature.
5.4 Ash-Cone Refractory Support—The ash cones shall be mounted on a refractory base composed of a mixture of equal parts
by weight of kaolin and alumina conforming to the following requirements:
5.4.1 Kaolin—NF-grade powder passing a 75-µm (No. 200) sieve.
5.4.2 Aluminum Oxide—Reagent grade ignited powder passing a 150-µm (No. 100) sieve.
5.5 Refractory Support Mold—A mold with flat top and bottom surfaces to provide a refractory support of suitable thickness
to minimize warping. A sidemold not over 6.4 mm ([ ⁄4 in.)in.] high of any convenient shape, placed on an iron plate so that the
topsurfaceoftherefractorymixcanbestruckoffflatandparalleltothebasebymeansofastraightedge,issatisfactory.Forelectric
furnace use, legs not over ⁄8 in. (3 mm)[3 mm] long may be provided on the corners of the cone support by suitable holes bored
in the iron base plate of the mold.
5.6 GoldWire —0.51-mmdiameter(twenty-fourgage)orlargerroundwireof99.98 %purity,butdrawnfrommetalof99.99 %
purity, and having a melting point of 1063°C (1945°F). [1945°F].
5.7 Nickel Wire —0.51-mm diameter (twenty-four gage) or larger round wire of CP nickel, 99.98 % pure, fully annealed, and
having a melting point of 1452°C (2645°F). [2645°F].
6. Test Atmosphere
6.1 Gas-Fired Furnace:
6.1.1 Reducing Atmosphere Test—A mildly reducing atmosphere surrounding the cones shall be maintained during the test in
the gas-fired furnace. Hydrogen, hydrocarbons, and carbon monoxide shall be considered as reducing gases; oxygen, carbon
dioxide, and water vapor shall be considered as oxidizing gases. Nitrogen is inert. The ratio by volume of reducing gases to
oxidizing gases in the atmosphere shall be between the limits of 20 to 80 and 80 to 20, that is, on a nitrogen-free basis, the total
amount of reducing gases present shall be between the limits of 20 and 80 volume %. A flame 152 to 203 mm (6[6 to 8 in.)in.]
in height and tinged with yellow above the furnace outlet has been found to provide an atmosphere within the specified limits.
6.1.2 Oxidizing Atmosphere Test—An atmosphere containing a minimum amount of reducing gases shall be maintained
surrounding the cones during the test in the gas-fired furnace. On a nitrogen-free basis, the volume of reducing gases present in
the atmosphere shall not exceed volume 10 %. Combustion with the maximum possible quantity of air with preservation of the
specifiedrateoftemperatureincreasehasbeenfoundtoprovideanatmospherewithinthespecifiedlimits.Acompletelyblueflame,
not over 50 mm (2 in.)[2 in.] in height above the outlet at the beginning of the test, provides the desired atmosphere; and, by
regulation of the combustion gas-air ratio, the specified atmosphere and temperature rise can be maintained.
6.2 Electric Furnace:
6.2.1 Reducing Atmosphere Test—A regulated flow of gas of the nominal composition, 60 % carbon monoxide and 40 6 5
volume % carbon dioxide, shall be maintained in the heating chamber throughout the test (Note 2) in the electric furnace. The
gas stream shall be regulated by any convenient means to provide a measured flow of 1.3 to 1.5 furnace volumes per minute.
6.2.2 Oxidizing Atmosphere Test—Aregulated stream of air shall be maintained throughout the test in the electric furnace. The
gas stream shall be regulated by any convenient means to provide a measured flow of 1.3 to 1.5 furnace volumes per minute.
NOTE 2—Before using new cylinders of CO/CO reducing gas, the contents should be mixed according to the gas manufacturer’s recommendations.
To assure that the gas remains mixed, the temperature of the cylinder contents should be maintained above the critical temperature at which CO can
liquify and separate.
7. Preparation of Ash
7.1 Use coal or coke passing a 250-µm (No. 60) sieve prepared in accordance with Method D2013, to obtain the ash by
incineration in a well-ventilated muffle furnace. The quantity of coal or coke required will vary with the ash content; usually 3 to
5 g of ash will be sufficient for cones for several check determinations, if necessary. Spread out the coal or coke in a layer not over
6.4 mm ([ ⁄4 in.)in.] in depth in a fireclay or porcelain roasting dish. Place the dish in the cold muffle or on the hearth at a low
temperature and gradually heat to redness at such a rate as to avoid mechanical loss from too rapid expulsion of volatile matter
(Note 3). Complete the conversion to ash at a temperature of 800 to 900°C (1470[1470 to 1650°F).1650°F]. Transfer the ash to
an agate mortar (Note 4) and grind it so that it will pass a 75-µm (No. 200) sieve. Then spread the ash in a thin layer in a fireclay,
silica, or porcelain dish and ignite it in a stream of oxygen for 1 ⁄2 h at 800 to 850°C (1470[1470 to 1560°F)1560°F] to ensure
complete and uniform oxidation of the ash.Any tube or muffle-type furnace which, when supplied with an oxygen flow of not less
than one furnace volume in 5 min, will maintain a highly oxidizing atmosphere and will be suitable.
Gold wire of this purity can be purchased from the Baker Dental Division of Engelhard Industries, Inc., 850 Passaic Ave., East Newark, NJ 07029 or from Leico
Industries, Inc., 250 W. 57th St., New York, NY 10019.
Nickel wire of this purity can be purchased with the additional specification of having a minimum coefficient of resistance for 0 to 100°C of 0.006 73 V/V·°C, from Leico
Industries, Inc., 250 W. 57th St., New York, NY 10019.
For information concerning the effect of various atmospheres, see U.S. Bureau of Mines Bulletin 129, 1918.
This gas is available from the Matheson Gas Co., Inc.
D1857/D1857M – 04 (2010)
NOTE 3—A heating rate conforming to that used for the ash determination specified in Section 7 of Test Method D3174 is satisfactory.
NOTE 4—A mechanical agate mortar grinder will save time where many determinations are made. An iron mortar or pestle must not be used.
8. Preparation of Cones
8.1 Thoroughly mix the ignited ash in a mechanical mixer or on a sheet of glazed paper or oil cloth by raising first one corner
to roll the ash over and then raising each of the other corners in rotation in the same manner until each corner has been raised five
times or more.
8.2 Take sufficient ash for the number of cones desired from various parts of the bulk ash. Moisten the ash with a few drops
of a clear, filtered (if necessary) 10 % solution of dextrin containing 0.1 % salicylic acid as a preservative and work it into
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