ASTM D4208-19

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of the standard as published by ASTM is to be considered the official document.
Designation: D4208 − 18 D4208 − 19
Standard Test Method for
Total Chlorine in Coal by the Oxygen Vessel Combustion/
Ion Selective Electrode Method
This standard is issued under the fixed designation D4208; 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*
1.1 This test method covers the analysis of total chlorine in coal.
1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard.
1.3 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D121 Terminology of Coal and Coke
D1193 Specification for Reagent Water
D3173 Test Method for Moisture in the Analysis Sample of Coal and Coke
D3180 Practice for Calculating Coal and Coke Analyses from As-Determined to Different Bases
E144 Practice for Safe Use of Oxygen Combustion Vessels
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 For definitions of terms used in this test method, refer to Terminology D121.
4. Summary of Test Method
4.1 Total chlorine is determined in this method by combusting a weighed sample in an oxygen combustion vessel with dilute
base adsorbing the chlorine vapors. The vessel is rinsed into a beaker with water and following the addition of an ionic strength
adjuster, the chloride is determined by ion-selective electrode.
5. Significance and Use
5.1 The purpose of this test method is to measure the total chlorine content of coal. The chlorine content of coals may be useful
in the evaluation of slagging problems, corrosion in engineering processes, and in the total analysis of coal and coke. When coal
samples are combusted in accordance with this method, the chlorine is quantitatively retained and is representative of the total
chlorine content of the whole coal.
6. Apparatus
6.1 Combustion Vessel, constructed of materials that are not affected by the combustion process or products. The vessel must
be designed so that all liquid combustion products can be quantitatively recovered by washing the inner surfaces. There must be
This test method is under the jurisdiction of ASTM Committee D05 on Coal and Coke and is the direct responsibility of Subcommittee D05.21 on Methods of Analysis.
Current edition approved Dec. 15, 2018Nov. 1, 2019. Published February 2019November 2019. Originally approved in 1982. Last previous edition approved in 20132018
as D4208 – 13.D4208 – 18. DOI: 10.1520/D4208-18.10.1520/D4208-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM 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.
*A Summary of Changes section appears at the end of this standard
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D4208 − 19
no gas leakage during the test. The vessel must be capable of withstanding a hydrostatic-pressure test to approximately 20 MPa
at room temperature without stressing any part beyond its elastic limit.
6.2 Water Bath—A container large enough to hold the combustion vessel and enough cooling water to dissipate the heat
generated during the combustion process. The container shall be designed to allow a constant flow of water around the combustion
vessel.
6.3 Combustion Crucibles—Samples shall be burned in an open crucible of platinum, quartz, or acceptable base-metal alloy.
6.4 Firing Wire, 100 mm, nickel-chromium alloy, No. 34 B & S gauge, or platinum, No. 34 or No. 38 B & S gauge.
6.5 Firing Circuit—A 6 V to 16 V alternating or direct current is required for ignition purposes with an ammeter or pilot light
in the circuit to indicate when current is flowing. A step-down transformer connected to an alternating-current lighting circuit or
batteries can be used. (Warning—The ignition circuit switch shall be of the momentary double-contact type, normally open,
except when held closed by the operator. The switch should be depressed only long enough to fire the charge.)
6.6 Balance, analytical, with a sensitivity of 0.1 mg.
6.7 Specific-Ion Meter—A pH meter with an expandable millivolt scale, specific-ion meter, sensitive to 0.1 mV, suitable for
method of standard addition determinations.
6.8 Electrodes, chloride-sensing, with the appropriate reference-type electrode as recommended by the manufacturer.
7. Reagents
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
7.2 Purity of Water, deionized, high-purity, low-specific conductivity, Type II reagent water as defined in Specification D1193.
7.3 Ionic Strength Adjuster Solution (5M NaNO )—Dissolve 42.5 g of sodium nitrate in 100 mL water.
7.4 Sodium Carbonate Solution (Na CO ) (2 %)—Dissolve 2.0 g of sodium carbonate in 100 mL water.
2 3
7.5 Chloride, Standard Stock Solution (1000 μg ⁄mL)—Dissolve 1.6486 g of sodium chloride (NaCl) in water and dilute to 1 L.
The NaCl should be dried for 1 h at 105 °C and cooled to room temperature in a desiccator before weighing.
7.6 Chloride, Standard Stock Solution (100 μg/mL)—Dilute 10.0 mL of chloride stock solution to 100 mL in a volumetric flask
with water.
7.7 Oxygen, free of combustible matter and guaranteed to be 99.99 % pure.
8. Sample
8.1 A convenient sample is the air-dried coal that must be pulverized to pass a No. 60 (250 μm) sieve.
8.2 A separate portion of the analysis sample shall be analyzed simultaneously for moisture content in accordance with Test
Method D3173 if calculation to other than the as-determined basis is desired.
9. Procedure for Vessel Combustion
9.1 Thoroughly mix the analysis sample of coal. Carefully weigh approximately 1 g 6 0.1 mg into a previously ignited crucible
in which it is to be combusted.
9.1.1 For samples in excess of 5 % sulfur, the mass of coal must be reduced to 0.5 g 6 0.1 g to ensure that all the acidic vapors
produced in the combustion process are quantitatively retained in solution.
9.2 Transfer 5 mL of 2 % Na CO solution into the combustion vessel. Attach the fuse wire to the vessel electrodes. Place the
2 3
crucible with the sample into the electrode support of the vessel, and insert the fuse wire so that it just touches the surface of the
sample.
9.3 Assemble the vessel in the normal manner and charge it with oxygen to a pressure between 2.0 MPa to 3.0 MPa. If the
oxygen should exceed the specified pressure, do not proceed with the combustion. In this case, detach the filling connection,
exhaust the vessel in the usual manner, and discard the sample. (Warning—The following precautions are recommended for safe
operations in the use of the oxygen combustion vessel. Additional precautions are given in Recommended Practice E144, for use
of oxygen combustion vessels.)
Midgley, D., and Torrance, K., Potentiometric Water Analysis, John Wiley and Sons, 1978.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.
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9.3.1 The weight of coal sample and the pressure of the oxygen admitted to the vessel must not exceed the vessel manufacturer’s
recommendation.
9.3.2 Inspect the vessel parts carefully after each use. Frequently check the threads on the main closure for wear. Replace the
cracked or significantly worn parts.
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