ASTM D5865/D5865M-19

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.
Designation:D5865/D5865M −19
Standard Test Method for
Gross Calorific Value of Coal and Coke
This standard is issued under the fixed designation D5865/D5865M; 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* D3177TestMethodsforTotalSulfurintheAnalysisSample
of Coal and Coke (Withdrawn 2012)
1.1 This test method pertains to the determination of the
D3180Practice for Calculating Coal and Coke Analyses
grosscalorificvalueofcoalandcokebyeitheranisoperibolor
from As-Determined to Different Bases
adiabatic combustion calorimeter.
D4239Test Method for Sulfur in the Analysis Sample of
1.2 The values stated in either SI units or inch-pound units
Coal and Coke Using High-Temperature Tube Furnace
are to be regarded separately as standard. The values stated in
Combustion
eachsystemarenotnecessarilyexactequivalents;therefore,to
D7582Test Methods for Proximate Analysis of Coal and
ensure conformance with the standard, each system shall be
Coke by Macro Thermogravimetric Analysis
used independently of the other, and values from the two
E144Practice for Safe Use of Oxygen Combustion Vessels
systems shall not be combined.
E178Practice for Dealing With Outlying Observations
1.3 This standard does not purport to address all of the E691Practice for Conducting an Interlaboratory Study to
safety concerns, if any, associated with its use. It is the
Determine the Precision of a Test Method
responsibility of the user of this standard to establish appro- E882Guide for Accountability and Quality Control in the
priate safety, health, and environmental practices and deter-
Chemical Analysis Laboratory
mine the applicability of regulatory limitations prior to use. E2251Specification for Liquid-in-Glass ASTM Thermom-
Specific hazard statements are given in Section 8.
eters with Low-Hazard Precision Liquids
1.4 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3.1 For additional definitions of terms used in this test
Development of International Standards, Guides and Recom-
method, refer to Terminology D121.
mendations issued by the World Trade Organization Technical
3.2 Definitions:
Barriers to Trade (TBT) Committee.
3.2.1 adiabatic calorimeter, n—a calorimeter that operates
in the adiabatic mode and may or may not use a microproces-
2. Referenced Documents
sor;theinitialtemperaturebeforeinitiatingthecombustionand
2.1 ASTM Standards:
the final temperatures are recorded by the operator or the
D121Terminology of Coal and Coke
microprocessor.
D346Practice for Collection and Preparation of Coke
3.2.2 automated calorimeter, n—a calorimeter which has a
Samples for Laboratory Analysis
microprocessor that takes the thermometric readings and cal-
D388Classification of Coals by Rank
culates the Calibration Value and the Heat of Combustion
D1193Specification for Reagent Water
Values.
D2013Practice for Preparing Coal Samples for Analysis
3.2.3 British thermal unit [Btu], n—the amount of heat
D3173Test Method for Moisture in theAnalysis Sample of
required to raise the temperature of one pound - mass [lbm] of
Coal and Coke
liquid water at one atmosphere pressure one degree Fahrenheit
at a stated temperature.
This test method is under the jurisdiction of ASTM Committee D05 on Coal
3.2.3.1 Discussion—The results of combustion calorimetric
and Coke and is the direct responsibility of Subcommittee D05.21 on Methods of
testsoffuelsforsteampowerplantsmaybeexpressedinterms
Analysis.
Current edition approved June 1, 2019. Published August 2019. Originally of the 1956 International Steam Table calorie (I.T. cal) which
approved in 1995. Last previous edition approved in 2013 as D5865–13. DOI:
isdefinedbytherelation,1I.T.cal=4.1868J.TheBtuusedin
10.1520/D5865_D5865M-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 last approved version of this historical standard is referenced on
theASTM website. www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5865/D5865M−19
modern steam tables is defined by the means of the relation, 5.2 The gross calorific value can be used for computing the
1I.T. cal/g = 1.8 I.T. Btu/lb. Thus, 1 I.T. Btu/lb = 2.326J⁄g. calorific value versus sulfur content to determine whether the
3.2.4 calorific value, n—the heat produced by combustion coal meets regulatory requirements for industrial fuels.
of a unit quantity of a substance under specified conditions.
5.3 The gross calorific value can be used to evaluate the
3.2.5 calorimeter, n—a device for measuring calorific value
effectiveness of beneficiation processes.
consisting of a combustion vessel, its contents, a vessel for
5.4 The gross calorific value can be required to classify
holdingthecombustionvessel,temperaturemeasuringdevices,
coals according to Classification D388.
ignition leads, water, stirrer, and a jacket maintained at
specified temperature conditions.
6. Apparatus and Facilities
3.2.6 gross calorific value (gross heat of combustion at
6.1 Test Area—An area free from drafts, shielded from
constant volume), Q (gross), n—the heat produced by com-
v
direct sunlight and other radiation sources. Thermostatic con-
plete combustion of a substance at constant volume with all
trol of room temperature and controlled relative humidity are
water formed condensed to a liquid.
desirable.
3.2.7 heat of formation, n—the change in heat content
resulting from the formation of 1mole of a substance from its
6.2 Combustion Vessel—Constructed of materials that are
elements at constant pressure.
not affected by the combustion process or the products formed
to introduce measurable heat input or alteration of end prod-
3.2.8 isoperibol calorimeter, n—a calorimeter that operates
ucts.Thecombustionvesselshallbedesignedsothatallliquid
in the isoperibol mode and uses a microprocessor to record the
combustion products can be completely recovered by washing
initialandfinaltemperaturesandmaketheappropiateheatleak
the inner surfaces. There shall be no gas leakage. The com-
corrections during the temperature rise; it determines when the
bustion vessel shall be capable of withstanding a hydrostatic
calorimeter is in equilibrium and ignites the sample and
pressure test to 20MPa [3000psig] at room temperature
determines when the calorimeter has reached equilibrium after
without stressing any part beyond its specified elastic limit.
ignition.
3.2.9 net calorific value (net heat of combustion at constant
6.3 Balance—Alaboratory balance capable of weighing the
pressure), Q (net), n—the heat produced by combustion of a analysis sample to the nearest 0.0001g. The balance shall be
p
substance at a constant pressure of 0.1MPa [1atm], with any
checked weekly, at a minimum, for accuracy.
water formed remaining as vapor.
6.4 Calorimeter Vessel—Made of metal with a tarnish-
3.3 Definitions of Terms Specific to This Standard:
resistant coating, with all outer surfaces highly polished. Its
3.3.1 corrected temperature rise, n—the calorimeter tem-
size shall be such that the combustion vessel is completely
perature change caused by the process that occurs inside the
immersed in water during a determination. A stirrer shall be
combustion vessel corrected for various effects.
provided for uniform mixing of the water. The immersed
portion of the stirrer shall be accessible to the outside through
3.3.2 heat capacity, n—the energy required to raise the
a coupler of low thermal conductivity. The stirrer speed shall
temperature of the calorimeter one arbitrary unit.
remain constant to minimize any temperature variations due to
3.3.2.1 Discussion—The heat capacity can also be referred
stirring. Continuous stirring for 10min shall not raise the
to as the energy equivalent or water equivalent of the calorim-
calorimeter temperature more than 0.01°C when starting with
eter.
identical temperatures in the calorimeter, test area, and jacket.
4. Summary of Test Method For calorimeters having a bucket it can be a separate compo-
nent or integral component of the combustion vessel. The
4.1 The heat capacity of the calorimeter is determined by
vesselshallbeofsuchconstructionthattheenvironmentofthe
burning a specified mass of benzoic acid in oxygen. A
calorimeter’s entire outer boundaries can be maintained at a
comparable amount of the analysis sample is burned under the
uniform temperature.
same conditions in the calorimeter. The calorific value of the
analysis sample is computed by multiplying the corrected 6.5 Jacket—Acontainerwiththeinnerperimetermaintained
temperature rise, adjusted for extraneous heat effects, by the
at constant temperature 60.1°C (isoperibol) or at the same
heat capacity and dividing by the mass of the sample.
temperature 60.1°C as the calorimeter vessel (adiabatic)
during the test. To minimize convection, the sides, top, and
4.2 Oxidation of coal after sampling can result in a reduc-
bottom of the calorimeter vessel shall not be more than 10mm
tionofcalorificvalue.Inparticular,ligniteandsub-bituminous
from the inner surface of the jacket. Mechanical supports for
rank coal samples may experience greater oxidation effects
the calorimeter vessel shall be of low thermal conductivity.
thansamplesofhigherrankcoals.Unnecessaryexposureofthe
samples to the air for the time of sampling or delay in analysis
6.6 Thermometers:
shall be avoided. (See X2.1.)
6.6.1 Platinum Resistance or Thermistor Thermometers
shall be capable of measuring to the nearest 0.0001°C. These
5. Significance and Use
types of thermometers consist of two major subsystems. The
5.1 The gross calorific value can be used to compute the first and most obvious is the temperature sensing probe itself.
total calorific content of the quantity of coal or coke repre- The second and equally important aspect is the measurement
sented by the sample for payment purposes. subsystem. For both subsystems, the relationship between the
D5865/D5865M−19
thermometer resistance and temperature shall be well charac- 7.2 Purity of Reagents—Use reagent grade chemicals con-
terized. The absolute temperature shall be known to 6 0.1°C forming to the specification of the Committee on Analytical
at the temperature of the calorimetric measurement. Reagents of the American Chemical Society in all tests.
6.6.2 Assessing the valid working range of the calorimeter,
7.3 Benzoic Acid—Standard (C H COOH)—Pellets made
6 5
as outlined in 10.9, is sufficient to demonstrate that all
from benzoic acid available from the National Institute of
important aspects of the calorimeter functionality, including
Standards and Technology (NIST) or benzoic acid calibrated
thethermometry,areingoodworkingorder.Thetraceabilityof
against NIST standard material. The calorific value of benzoic
the heat of combustion measurement is governed by the
acid,foruseinthecalibrationcalculations,shallbetraceableto
traceability of the heat of combustion of the benzoic acid
a recognized certificate value.
calibrant in addition to meeting the aforementioned criteria.
7.4 Oxygen—Manufactured from liquid air, guaranteed to
6.6.3 Liquid-in-Glass Thermometers—Conforming to the
be greater than 99.5% pure, and free of combustible matter.
requirements for thermometers S56C, S116C, or S117C as
Oxygen made by the electrolytic process contains small
prescribed in Specification E2251.
amounts of hydrogen rendering it unfit unless purified by
6.6.3.1 Thermometer Accessories—A magnifier is required
passage over copper oxide at 500°C.
for reading liquid-in-glass thermometers to one tenth of the
smallest scale division. The magnifier shall have a lens and
7.5 Titration Indicator—Methyl orange, methyl red, or
holderdesignedsoastominimizeerrorsasaresultofparallax. methyl purple for indicating the end point when titrating the
acid formed during combustion. The same indicator shall be
6.7 Sample Holder—An open crucible of platinum, quartz,
used for both calibration and calorific value determinations.
or base metal alloy. Before use in the calorimeter, heat treat
base metal crucibles for a minimum of 4h at 500°C to ensure
7.6 Standard Solution—Sodium carbonate (Na CO)or
2 3
the crucible surface is completely oxidized. Base metal alloy
othersuitablestandardsolution.Aconvenientstandardsolution
crucibles are acceptable, if after three preliminary firings, the
may be prepared as follows. Dissolve 3.706g of sodium
mass does not change by more than 0.0001g.
carbonate, dried for 24h at 105°C, in water and dilute to 1L.
The resulting concentration (0.0699 N) assumes the energy of
6.8 Ignition Fuse—Ignition fuse of 100mm length and
formation of HNO under combustion vessel conditions is
0.16mm [No.34 B&S gauge] diameter or smaller. Nickel-
-59.7kJ⁄mol[-14.3kcal⁄mole](seeX1.1).Onemilliliterofthis
chromium alloy (Chromel C) alloy, cotton thread, or iron wire
solution is equivalent to 4.2J [1.0cal] in the acid titration.
are acceptable. Platinum or palladium wire, 0.10mm diameter
Alternatively, 1.0mLof a 0.1000 N base solution is equivalent
[No.38 B&S gauge], can be used provided constant ignition
to 6.0J [1.4cal] in the acid titration. In general, 1 mL of an
energy is supplied. Use the same type and length (or mass) of
arbitrary standard titrant solution is equivalent to its concen-
ignition fuse for calorific value determinations as used for
tration (equivalents/liter or normality [N]) times 59.7 J
standardization.
[14.3cal].
6.9 Ignition Circuit—A 6V to 30V alternating or direct
current is required for ignition purposes. A step-down trans-
8. Hazards
former connected to an alternating current circuit, capacitors,
8.1 The following precautions are recommended for safe
or batteries can be used. For manually operated calorimeters,
calorimeter operation. Additional precautions are noted in
the ignition circuit switch shall be of the momentary double-
Practice E144. Also consult the calorimeter equipment manu-
contact type, normally open except when held closed by the
facturer’s installation and operating instructions before using
operator.Anammeterorpilotlightcanbeusedinthecircuitto
the calorimeter.
indicate when current is flowing.
8.1.1 Themassofsampleandanycombustionaidaswellas
6.10 Controller—For automated calorimeters, capable of
the pressure of the oxygen admitted to the combustion vessel
charging the combustion vessel; filling the calorimeter vessel;
shall not exceed the combustion vessel manufacturer’s speci-
firing the ignition circuit; recording calorimeter temperatures
fications.
before, during, and after the test; recording the balance
8.1.2 Inspect the combustion vessel parts carefully after
weights; and carrying out all necessary corrections and calcu-
each use. Replace cracked or significantly worn parts. Replace
lations.
O-rings and valve seats in accordance with manufacturer’s
6.11 Crucible Liner—Quartz fiber or alundum for lining the instruction. For more details, consult the manufacturer.
crucible to promote complete combustion of samples that do 8.1.3 Equip the oxygen supply cylinder with an approved
not burn completely during the determination of the calorific type of safety device, such as a relief valve, in addition to the
value. needle valve and pressure gauge used in regulating the oxygen
feed to the combustion vessel. Valves, gauges, and gaskets
7. Reagents
shall meet industry safety codes. Suitable reducing valves and
7.1 Reagent Water—Conforming to conductivity require-
ments for Type II of Specification D1193 for preparation of
Reagent Chemicals, American Chemical Society Specifications, American
reagents and washing of the combustion vessel interior.
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory
Supporting data have been filed atASTM International Headquarters and may Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
beobtainedbyrequestingResearchReportRR:D05-1025.ContactASTMCustomer and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
Service at service@astm.org. MD.
D5865/D5865M−19
adapters for 3MPa to 4MPa [300psig to 500psig] discharge stability shall be 60.001°C for an adiabatic calorimeters and
pressure can be obtained from commercial sources of com- 60.001°C⁄s or less for an isoperibol calorimeter.
pressed gas equipment. Check the pressure gauge annually for 10.4.2 Extrapolation Method—Fire the charge, record the
accuracy or after any accidental over pressures that reach temperaturerise.Thetestcanbeterminatedwhentheobserved
maximum gauge pressure. thermal curve matches a thermal curve which allows extrapo-
8.1.4 During ignition of a sample, the operator shall not lation to a final temperature with a maximum uncertainty of
extend any portion of the body over the calorimeter. 60.002°C.
8.1.5 Do not fire the combustion vessel if the combustion 10.4.3 Full Development Method—Fire the charge and re-
vessel has been dropped or turned over after loading. cord the temperature rise until the temperature has stabilized
8.1.6 Do not fire the combustion vessel if there is evidence for a period of 30s in accordance with the stability require-
ofgasleakagewhenthecombustionvesselissubmergedinthe ments specified in 10.4.1.
calorimeter vessel.
10.5 Temperature Observations Manual Calorimeters:
8.1.7 For manually operated calorimeters, the ignition
10.5.1 WhenusingASTMThermometersS56C,estimateall
switch shall be depressed only long enough to fire the charge.
readings to the nearest 0.002°C. When using ASTM Ther-
mometers S116C or S117C, estimate readings to 0.001°C and
9. Sample
25 Ω resistance thermometer readings to the nearest 0.0001 Ω.
9.1 The analysis sample is the material pulverized to pass Tap or vibrate liquid-in-glass thermometers just before reading
to avoid errors caused by liquid sticking to the walls of the
250µm [No.60] sieve, prepared in accordance with either
Practice D346 for coke or Practice D2013 for coal. capillary.
10.5.2 Allow 5min for the temperature of the calorimeter
vessel to stabilize. Adjust the jacket temperature to match the
10. Determination of the Heat Capacity of the
calorimetervesseltemperaturewithin0.01°Candmaintainfor
Calorimeter
3min.
10.1 Sample—Weigh 0.8g to 1.2g of benzoic acid into a
10.5.3 Fire the charge. Record the time as a and the
sample holder. Record sample mass to the nearest 0.0001g.
temperature as t .
a
10.2 Preparation of Combustion Vessel:
10.5.4 For adiabatic calorimeters adjust the jacket tempera-
10.2.1 Rinse the combustion vessel with water to wet
ture to match that of the calorimeter vessel temperature during
internal seals and surface areas of the combustion vessel or
the period of the rise. Keep the two temperatures as equal as
precondition the calorimeter according to the manufacturer’s
possible during the period of rapid rise. Adjust to within
instructions. Add 1.0 mL of water to the combustion vessel
0.01°C when approaching the final stabilization temperature.
before assembly.
Record subsequent readings at intervals no greater than 1min
10.2.2 Connect a measured fuse in accordance with manu-
until three successive readings do not differ by more than
facturer’s guidelines.
60.001°C. Record the first reading after the rate of change
10.2.3 Assemble the combustion vessel. Admit oxygen to
has stabilized as the final temperature t and the time of this
c
the combustion vessel to a consistent pressure of between
readingasc.Forisoperibolcalorimeters,whenapproachingthe
2MPa and 3MPa [20atm and 30atm]. The same pressure is
final stabilization temperature, record readings until three
used for each heat capacity run. Control oxygen flow to the
successive readings do not differ by more than 0.001°C per
combustion vessel so as not to blow material from the sample
min. Record the first reading after the rate of change has
holder. If the pressure exceeds the specified pressure, detach
stabilized as the final temperature as t and the time of this
c
the filling connection and exhaust the combustion vessel.
reading as c.
Discard the sample.
10.5.5 Combustion Vessel Depressurization—When the
thermochemical corrections will be made by titration, the
10.3 Preparation of Calorimeter:
depressurization and subsequent rinse collection shall be done
10.3.1 Fill the calorimeter vessel with water at a tempera-
in a manner ensuring at least 80% recovery of the acidic
ture not more than 2°C below room temperature and place the
combustion products. An effective measure of the recovery is
assembled combustion vessel in the calorimeter. Check that no
offered by the recovery factor described in the following
oxygen bubbles are leaking from the combustion vessel. If
section. Depressurization at a rate such that the operation is
there is evidence of leakage, remove and exhaust the combus-
not less than 1min provides effective recovery and does not
tion vessel. Discard the sample.
require validation.There are no special requirements related to
10.3.2 The mass of water used for each test run shall be M
the combustion vessel depressurization if the calculated nitric
6 0.5 g where M is a fixed mass of water. Devices used to
acid procedure is used.
supply the required mass of water on a volumetric basis shall
10.5.5.1 Determinetherecoveryfactorfromtheslopeofthe
be adjusted when necessary to compensate for change in the
straight line resulting from the regression analysis of the
density of water with temperature.
10.3.3 With the calorimeter vessel positioned in the jacket
start the stirrers.
Supporting data have been filed atASTM International Headquarters and may
10.4 Temperature Observations Automated Calorimeters:
be obtained by requesting Research Report RR:D05-1028, “Interlaboratory Study
10.4.1 Stabilization—The calorimeter vessel’s temperature
fortheUseofCalculatedNitricAcidCorrection.”ContactASTMCustomerService
shall remain stable over a period of 30s before firing. The at service@astm.org.
D5865/D5865M−19
titration results (mg of sulfur versus meq) using three or more Example:
samples with at least two different sulfur concentrations that The nitric acid correction for a 340mL oxygen combustion
vesselisfoundtobe41.9J[10.0cal]whenthereleasedenergy
span the range of sulfur values typically encountered in the
corresponds to that liberated by 1g of benzoic acid, 26.45kJ
laboratory. One equivalent of sulfuric acid (1000meq) is
[6318cal]. The ratio of these quantities is 1.58J per 1000J of
formed from 16.03g of sulfur. A plot of sulfur (mg) versus
releasedenergyor1.58calper1000calofreleasedenergy.The
milliequivalents (meq) of titrant used to neutralize the com-
nitric acid correction for any calorimetric test can then be
bustion vessel rinsings has a theoretical slope of 16.03. The
expressed as follows:
milliequivalents of titrant is the product of milliliters of base
used and its concentration (normality). The mass of sulfur in
e 51.58*energy released for the test ~kJ or kcal! (2)
the sample in milligrams is the product of the sulfur concen- For a given calorimeter, the energy released in the combus-
tion vessel during a test for the purposes of calculating the
tration in weight percent in the analysis sample, the sample
nitric acid correction (e ) may be expressed as the product of
massandten.Aslopeof16implies100%recovery.Increasing
the temperature rise for the test and the effective calorimeter
values are indicative of diminished recovery. For example, a 7
heat capacity or calorimeter calibration factor.
value of 20 indicates 80% recovery (16.03 × 100/20 = 80%).
e 5 1.58/1000 *E*t (3)
~ !
10.5.6 After depressurization, open the combustion vessel
The calculated nitric acid method can be applied to samples
and examine the combustion vessel interior carefully for signs
containing up to 2% nitrogen without introducing a signifi-
cant error in the resulting heat of combustion value.
of unburned material or sooty deposits. Discard the test result
if either is observed.
10.6.2 Fuse Correction (see X1.3)—Determine the fuse
correction using one of the two alternatives:
10.6 Thermochemical Corrections (see Appendix X1):
10.6.2.1 Measure the combined pieces of unburned ignition
10.6.1 Acid Correction (see X1.1)—One may use either the
fuseandsubtractfromtheoriginallengthtodeterminethefuse
titration (10.6.1.1) or calculated titration (10.6.1.2) procedure
consumed in firing according to Eq 4.
for coal and coke samples.
e 5 K 3l (4)
10.6.1.1 Titration Method—Wash the interior of the com- 2 l
bustion vessel with distilled water containing the titration
where:
indicator (see 7.5) until the washings are free of acid and
e = the correction for the heat of combustion of the firing
combine with the rinse of the capsule. Titrate the washings
fuse,
with the standard solutions (see 7.6) using a titration indicator,
l = the length of fuse consumed during combustion,
orapHormillivoltmeter.Theproductofthevolumeoftitrant
K = 0.96J⁄mm [0.23cal⁄mm] for No. 34 B&S gauge
l
used in milliliters, the concentration of the standard solution
Chromel C,
(normality) and 59.7J [14.3cal] shall be taken as e . K = 1.13J⁄mm [0.27cal⁄mm] for No. 34 B&S gauge iron
1 l
wire, and
10.6.1.2 Calculated Nitric Acid Method—For test samples
K = 0.00J⁄mm for platinum or palladium wire provided
that contain no nitrogen, the nitric acid formed in the combus- l
the ignition energy is constant.
tion vessel during the combustion process is derived from the
nitrogen in the air that occupies the combustion vessel prior to or;
10.6.2.2 Weigh the combined pieces of unburned fuse and
pressurizing it with oxygen.The quantity of nitric acid formed
subtract from the original mass to determine the mass in
is a function of the volume of the combustion vessel, the
milligramsofthefuseconsumedinfiring(m).Removeanyball
oxygen filling pressure, and the quantity of energy released in
of oxidized metal from the ends before weighing.
the combustion vessel during a test. For a given combustion
vesselandfillingpressure,therelationshipbetweentheamount
e 5 K 3m (5)
2 m
ofnitricacidformedandtheenergyreleasedcanbedetermined
where:
using the following procedure. The calorimeter should be
e = the correction for the heat of combustion of the firing
tested using 1g pellets of benzoic acid when the combustion
fuse,
vessel volume is nominally 340 mL. If the combustion vessel
m = the mass in mg of fuse consumed during combustion,
volume differs significantly from 340 mL, the sample mass
usedshouldbeadjustedasrequiredinordertocomplywiththe
K = 5.9J⁄mg[1.4cal/mg]forNo.34B&SgaugeChromel
m
combustion vessel manufacturer’s safe operating guidelines.
C,
Tests should be run in duplicate. Determine the nitric acid
K = 7.5J⁄mg [1.8 cal/mg] for No. 34 B&S gauge iron
m
correction by titrating the combustion vessel washings as
wire, and
outlined in 10.6.1.1. Divide the correction obtained (e ) by the
K = 0.00J⁄mg for platinum or palladium wire provided
m
amount of energy released in the combustion vessel for the
the ignition energy is constant.
corresponding test. The energy contribution from the ignition
fuse (e ) is usually small (<1% of the total energy released)
and may be ignored. The average value of this ratio is used to
establishafactor(NAF)thatallowsthenitricacidcorrectionto Supporting data have been filed atASTM International Headquarters and may
be obtained by requesting Research Report RR:D05-1028, “Interlaboratory Study
be determined for any arbitrary energy release.
fortheUseofCalculatedNitricAcidCorrection.”ContactASTMCustomerService
e 5 NAF *energy released for the test (1) at service@astm.org.
~ !
D5865/D5865M−19
When cotton thread is used, employ the correction in J formingadditionalcalibrationmeasurementsasrequired.Table
recommended by the instrument manufacturer. 1providesanexamplesummaryofaseriesofcalibrationtests.
The formulas used to arrive at the mean value and relative
10.7 Calculation of the Corrected Temperature Rise—
standard deviation are independent of the units used for the
Compute the corrected temperature rise, t, as follows:
calibration measurements.
t 5 t 2 t 1C 1C (6)
c a e r
10.9 Valid Working Range for the Calibration of the Calo-
where:
rimeter:
t = corrected temperature rise, °C;
10.9.1 It is a generally accepted principle of reliable analy-
t = initial temperature reading at time of firing;
sis that instruments should be calibrated over the full range of
a
t = final temperature reading;
c measurement and that measurements be restricted to the range
C = thermometer, emergent stem correction (see Eq A1.6
e calibrated. It is not good practice to report extrapolated data
or Eq A1.8); and
obtained outside the range of calibration.The range of reliable
C = radiation correction (see Eq A1.1 or Eq A1.2).
r
calibration can be considered as the range of reliable measure-
ment and vice versa.
10.7.1 The temperature rise in isoperibol calorimeters re-
10.9.2 It should be possible to vary the amount of benzoic
quires a radiation correction.
acid calibrant by at least 625% without observing a signifi-
10.8 Calculation of the Heat Capacity—Calculate the heat
cant trend in the values obtained for the effective heat capacity
capacity (E) of the calorimeter using the following equation:
or instrument calibration factor. The working limits for the
E 5 H 3m 1e 1e /t (7)
@~ ! #
c 1 2
instrumentcalibrationshallbedeterminedanddefinedinterms
ofthecorrectedtemperaturerise.Allsubsequentmeasurements
where:
shall be kept within these limits.
E = the calorimeter heat capacity, J/°C;
10.9.3 A convenient way to check a previously calibrated
H = heat of combustion of benzoic acid, as stated in the
c
instrument is to use benzoic acid as an unknown. The mean
certificate, J/g;
value for the heat of combustion from duplicate runs using
m = mass of benzoic acid, g;
0.7g and 1.3g sample masses, respectively, should be within
e = acid correction from 10.6.1 from either the titration
656J⁄g or 624Btu⁄lb of the accepted heat of combustion
method(10.6.1.1)orthecalculatedtitration(10.6.1.2);
value.
10.9.4 For any given instrument, examination of the appli-
e = fuse correction from 10.6.2,J;and
cable range of the instrument calibration should be carried out
t = corrected temperature rise from 10.7,°C.
when the instrument is new, moved to a different location, or
10.8.1 Using the procedures described in 10.1 – 10.8
subject to major repair.
complete a total of ten acceptable test runs.An individual test
shall be rejected only if there is evidence of incomplete
11. Calibration Verification
combustion.
10.8.2 The precision of ten acceptable calibration test runs 11.1 The calorimeter calibration shall be checked on a
shall have a relative standard deviation (RSD) no greater than regular basis. Renewed determination of the heat capacity is
0.17%. If after considering the possibility of outliers using required whenever significant alterations have been made to
criteria established in Practice E178, this limit is not met, one the instrument or to the test conditions. The optimum fre-
should review operation of the calorimeter for any assignable quencyforcheckingtheheatcapacityorinstrumentcalibration
cause. Operating deficiencies should be corrected before per- willdependonthestabilityofthemeasurementsystemandthe
TABLE 1 Calibration Measurments
Column A Column B
Run Number Heat Capacity Difference from
J/°C Average Squared
1 10 258 20
2 10 249 20
3 10 270 272
4 10 254 0
5 10 245 72
6 10 249 20
7 10 241 156
8 10 266 156
9 10 258 20
10 10 245 72
Sum 102 535 811
Average 10 254 Sum Column A /10
Variance (s ) 90 Sum Column B /9
Standard Deviation(s) 9 Sqrt (Variance)
Relative Standard Deviation (RSD) 0.09 % s/Average * 100
D5865/D5865M−19
risk involved when the system departs from statistical control. area in which almost all (99.7%) of the plotted points are
Sincealldataobtainedduringtheperiodlast-known-in-control expected to lie when the system is in a state of statistical
to first-known-out-of-control are suspect, such intervals may control. It should be clear that when more than 5% of the
need to be minimized. points(1in20)lieoutsideofthewarninglimitsorwhenvalues
fall outside of the control limits the system is behaving
11.1.1 There are several empirical approaches to deciding
unexpectedlyandcorrectiveactions,andevenrejectionofdata,
on how frequently the instrument calibration should be
may be required.
checked. The experience of the laboratory may indicate the
11.2.3 Results are expected to scatter with a normal distri-
expected frequency of occurrence of trouble, in which case
bution within the limits. Systematic trends or patterns in the
reference sample measurements, at least three in number,
data plots may be early warning of incipient problems and are
should be equally spaced within such an interval. Another
cause for concern; hence techniques to identify such should be
approach is the "length of run" concept. In this, recognizable
breaks in the production (of data) process are identified which practiced.
11.2.4 Control charts, including the factors for calculating
could cause significant changes in precision or bias. Such
breaks could include change of work shift; rest periods; control limits are discussed more thoroughly elsewhere (see
GuideE882and (1) .Thecentrallineiseithertheknownvalue
change, modification, or adjustment of apparatus; use of new
for the test sample (for example, certified value), or the mean
calibration standards; significantly long down-times; use of a
of 10 sets of independent measurements. Control limits are
new lot of reagents.At least three reference samples should be
then calculated according to the following relationships.
measured during any of these periods when the periods are
considered to be potentially significant.
UCL Mean or accepted value+3*sigma/sqrt(N)
UWL Mean or accepted value+2*sigma/sqrt(N)
11.1.2 Periodic checks of the instrument calibration are a
Central Line Mean of the 10 most recent measurements or the
risk-reducing procedure. However, if it involves more than
X(bar) accepted value.
10% of a laboratory’s measurement effort, either the quality LWL Mean or accepted value–2*sigma/sqrt(N)
LCL Mean or accepted value–3*sigma/sqrt(N)
control process may need improvement or too much effort is
For the above limits, N represents the number of repetitive
being exerted in this direction. If less than 5% of effort is
measurements of the reference sample, the mean of which is
devoted to such measurements, the laboratory may be taking
plotted on an Xbar chart. For an X chart (single measurement
toohighariskofproducingunacceptabledata,ormaynoteven
of the reference sample) N = 1. The standard deviation of the
know the quality of the data it is producing. The above
measurementprocessissigma.Sigmaistakenas0.10%ofthe
statements are made with a laboratory making a significant
mean of the ten most recent measurements or 0.10% the
number of high-quality routine measurements in mind. If a
accepted value if tests are being performed using a reference
laboratory’s program involves occasional or one-of-a-kind
material, for example benzoic acid, run as an unknown. Table
measurements,theamountofqualityassuranceeffortrequired,
2 illustrates important selected control limits for calorimeter
including the number of measurements of reference materials
operation when benzoic acid is used as a test sample.
to be made may be significantly more than that indicated
above.
11.3 Rolling Average Method:
11.1.3 Two complementary procedures are offered for
11.3.1 The mean value of the ten most recent calorimeter
calorimeter calibration verification: Control Chart Method and
calibration or heat capacity measurements is used to support
Rolling Average Method.
the calibration of the calorimeter system. A single new value,
incorporated into the average of the ten most recent
11.2 Control Chart Method for Calibration Verification:
measurements, discarding the oldest measurement in the exist-
11.2.1 A control chart is a graphical way to interpret test
ing series of ten measurements first, must meet the precision
data. In its simplest form, a selected reference sample is
requirements outlined in 10.8.2.
measured periodically and the results are plotted sequentially
(or time-ordered) on a graph. Limits for acceptable values are 11.4 Recommended Test Substances:
11.4.1 By international agreement in the 1920’s, benzoic
defined and the measurement system is assumed to be in
control(variabilityisstableandduetochancealone)aslongas acid was selected as the chemical standard to be used in
calibrating combustion vessel calorimeters. Today, it remains
the results stay within these limits.The residence of the values
within expected limits is accepted as evidence that the preci- as the sole chemical primary standard for this type of calibra-
tion.
sion of measurement remains in control. The monitored preci-
sion of measurement and the accuracy of measurement of the 11.4.1.1 Ingeneral,thecalibrationofananalysisinstrument
consists of the evaluation of its response function in terms of
reference sample may be transferred, by inference, to all other
appropriate measurements made by the system while it is in a the composition of the analyte. The instrument responds to
some property of the analyte, the value of which needs to be
state of control.
quantified by use of known substances. It is tacitly assumed
11.2.2 A control chart can be realized by sequentially
that the instrument will respond analogously to the standard
plotting individual measurement values. The central line is the
and test samples. With this in mind, the confidence in the
most probable value (that is, the grand average) of all the
measurements or the accepted measurement value. The limits
LWLtoUWL(lowerandupperwarninglimits)definethearea
in which 95% of the plotted points are expected to lie. The
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
limits LCLto UCL(lower and upper control limits) define the this standard.
D5865/D5865M−19
TABLE 2 Calorimeter Control Limits When Benzoic Acid is Used as a Test Sample
NOTE 1—Accepted heat of combustion taken as 26454J⁄g
Process sigma is 0.10% RSD
Control limits based on 99% confidence (3 sigma) values
Values are in J/g except as noted.
Number of UCL for the range UCL for the RSD Maximum Permissible Deviation
Observations in a (High-Low) within the within the Group of the Group Mean from the
Group Group Accepted Value or Grand Mean
1 . . 79.4
2 97.5 0.2606 56.1
3 115.3 0.2276 45.8
4 124.3 0.2088 39.7
5 130.1 0.1964 35.5
6 134.3 0.1874 32.4
7 137.6 0.1806 30.0
8 140.4 0.1751 28.1
9 142.7 0.1707 26.5
10 144.7 0.1669 25.1
15 151.8 0.1554 20.5
20 156.7 0.1470 17.7
25 160.2 0.1420 15.9
FIG. 1Example of X Chart for Calibration Runs
-1A
measurement process is influenced by the uncertainty in
Substance -∆ u /Jg
B
Acetanilide 31 279 (2)
composition of known samples and the soundness of the
CAS 103-84-4
analogy.
CH3CONHC6H5
11.4.1.2 It is desirable to perform check experiments in
MWT 135.17
Density 1.22 g/cc
order to demonstrate confidence in the ability to make mea-
Tris (hydroxymethyl) aminomethane 20 058 (3)
surements on unknowns that are not only acceptably precise
CAS 77-86-1
butalsoacceptablyaccurate.Thisisespeciallytrueininstances (HOCH2)3-CNH2
MWT 121.14
where conditions in the calibration and combustion tests differ
Density = 1.35 g/cc
appreciably. For example, large differences in the rates of
combustion between the calibrant and the unknown or signifi-
A
Mass against stainless steel weights (8 g/cc) in air (0.0012 g/cc).
cant differences in combustion chemistries may give rise to
11.4.2.1 Both acetanilide and tris (hydroxymethyl) amin-
systematic errors that are difficult to detect. The use of test
omethane are available in high purity, are non-hygroscopic,
substances in such check experiments can help demonstrate
thatthetechniquesandproceduresusedindeterminingheatsof and have very low vapor pressure. Acetanilide is available
from NIST as a micro-analytical standard for CHON com-
combustion of unknown materials are reasonably free of
persistent errors. pounds (SRM 141). Tris (hydroxymethyl) aminomethane is
11.4.2 For work with solid samples, the following test also available from NIST as an acidimetric standard
substances are recommended. (SRM723).
D5865/D5865M−19
FIG. 2Example of X Chart for Check Sample Runs
11.4.2.2 Both materials are commercially available. When number of replicate analyses by one or several laboratories. In
the aforementioned materials are used as secondary thermo- practice,thismaterialcanbeusedtoassesstheperformanceof
chemical standards or test substances for combustion a single laboratory, as well as to determine the degree of
calorimetry, ensure that the minimum stated purity is at least comparability among different laboratories.
99.9%. 11.5.2 A significant amount of work is involved with the
11.4.2.3 Crystalline tris (hydroxymethyl) aminomethane is production and maintenance of any LCM. For example,
difficult to form into a durable pellet. Its relatively low heat of materials related issues such as stability, homogenization
combustion value allows this material to be weighed directly techniques, and proper conditions for storage must be ad-
into the combustion crucible and combusted in this form. dressed. For smaller laboratories, the time and effort involved
Whenaconsumablemetalfusewireisused,thewireloopshall in supporting the use of true LCMs may not be justified. In
be in direct contact with the granular sample. such cases, the use of CRMs is preferred.
11.4.2.4 Acetanilide is easily formed into a 12.5mm diam- 11.5.3 Routine analysis of CRMs or LCMs represent an
eterpelletandshallbeburnedinthisformduetoitshigherheat important aspect of a performance-based QA philosophy. At
of combustion value. least one CRM or LCM must be analyzed along with each
11.4.2.5 The nitric acid correction for tests involving the batch of 20 or fewer samples (that is, QA samples should
recommended test substances is approximately 50% higher comprise a minimum of 5% of each set of samples). For
than what is typically obtained for benzoic acid calibrant CRMs,thecertifiedheatofcombustionvaluewillbeknownto
samples. This is a consequence of the single nitrogen atom the analyst(s) and will be used to provide an immediate check
associated with each of the test materials. About 10% of this on performance before proceeding with a subsequent sample
nitrogen gives rise to aqueous nitric acid during the high batch. Performance criteria for both precision and accuracy
pressure combustion process. The remainder appears as el- must be established for the analysis of CRMs or LCMs using
emental nitrogen in the combustion products. The additional a given instrumental technique. If the laboratory fails to meet
correction is accounted for transparently when the titration eithertheprecisionoraccuracycontrollimitcriteriaforagiven
method is used to arrive at the acid correction. When the analysis of the CRM or LCM, the data for the entire batch of
calculated nitric acid method is used, the nitric acid factor samples is suspect. Potential operating deficiencies must be
(NAF) shall be increased by 50% when applied to tests checked / corrected and the CRM or LCM may have to be
involving these test substances. reanalyzed to confirm the results. If the values are still outside
the control limits in the repeat analysis, the laboratory is
11.5 Use of Laboratory Control Materials:
required to find and eliminate the source(s) of the problem and
11.5.1 A laboratory control material (LCM) is similar to a
repeat the analysis of that batch of samples until control limits
certified reference material in that it is a homogeneous matrix
are met, before final data are
...