SIST EN ISO 9831:2004
(Main)Animal feeding stuffs, animal products, and faeces or urine - Determination of gross calorific value - Bomb calorimeter method (ISO 9831:1998)
Animal feeding stuffs, animal products, and faeces or urine - Determination of gross calorific value - Bomb calorimeter method (ISO 9831:1998)
Futtermittel, tierische Produkte und Kot oder Urin - Bestimmung des effektiven Brennwerts - Verfahren mit der kalorimetrischen Bombe (ISO 9831:1998)
Diese Internationale Norm legt ein Verfahren zur Bestimmung des kalorischen Bruttowertes von Futtermitteln, tierischen Produkten und Kot oder Urin bei konstantem Volumen in einem adiabatischen, isothermen oder statischen Bombenkalorimeter fest.
Das mit diesem Verfahren gewonnene Ergebnis ist der kalorische Bruttowert der Prüfprobe bei konstantem Volumen, wobei das Wasser der Verbrennungsprodukte bei der Temperatur des Kalorimeters in den flüssigen Zustand kondensiert wird.
ANMERKUNG Die internationale Referenztemperatur von 25 °C für die Thermochemie wird als Referenztemperatur für den kalorischen Wert verwendet, obgleich die Temperaturabhängigkeit des kalorischen Wertes der Materialien, für die diese Internationale Norm gilt, gering ist (etwa 1 J × g-1 × K-1).
Aliments des animaux, produits d'origine animale et excréments ou urines - Détermination de la valeur calorifique brute - Méthode a la bombe calorimétrique (ISO 9831:1998)
Krma živalskega izvora, živalski proizvodi, blato, urin - Ugotavljanje skupne energijske vrednosti - Metoda s kalorimetrom (ISO 9831:1998)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 9831:2004
01-maj-2004
Krma živalskega izvora, živalski proizvodi, blato, urin - Ugotavljanje skupne
energijske vrednosti - Metoda s kalorimetrom (ISO 9831:1998)
Animal feeding stuffs, animal products, and faeces or urine - Determination of gross
calorific value - Bomb calorimeter method (ISO 9831:1998)
Futtermittel, tierische Produkte und Kot oder Urin - Bestimmung des effektiven
Brennwerts - Verfahren mit der kalorimetrischen Bombe (ISO 9831:1998)
Aliments des animaux, produits d'origine animale et excréments ou urines -
Détermination de la valeur calorifique brute - Méthode a la bombe calorimétrique (ISO
9831:1998)
Ta slovenski standard je istoveten z: EN ISO 9831:2003
ICS:
65.120 Krmila Animal feeding stuffs
SIST EN ISO 9831:2004 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 9831:2004
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SIST EN ISO 9831:2004
EUROPEAN STANDARD
EN ISO 9831
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2003
ICS 65.120
English version
Animal feeding stuffs, animal products, and faeces or urine -
Determination of gross calorific value - Bomb calorimeter
method (ISO 9831:1998)
Aliments des animaux, produits d'origine animale et Futtermittel, tierische Produkte und Kot oder Urin -
excréments ou urines - Détermination de la valeur Bestimmung des effektiven Brennwerts - Verfahren mit der
calorifique brute - Méthode à la bombe calorimétrique (ISO kalorimetrischen Bombe (ISO 9831:1998)
9831:1998)
This European Standard was approved by CEN on 13 November 2003.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2003 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9831:2003 E
worldwide for CEN national Members.
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SIST EN ISO 9831:2004
EN ISO 9831:2003 (E)
Foreword
The text of ISO 9831:1998 has been prepared by Technical Committee ISO/TC 34 "Agricultural
food products” of the International Organization for Standardization (ISO) and has been taken
over as EN ISO 9831:2003 by Technical Committee CEN/TC 327 "Animal feeding stuffs -
Methods of sampling and analysis", the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by May 2004, and conflicting national standards
shall be withdrawn at the latest by May 2004.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium, Czech
Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and
the United Kingdom.
Endorsement notice
The text of ISO 9831:1998 has been approved by CEN as EN ISO 9831:2003 without any
modifications.
NOTE Normative references to International Standards are listed in annex ZA (normative).
2
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SIST EN ISO 9831:2004
EN ISO 9831:2003 (E)
Annex ZA
(normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications, indicated
by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 3696 1987 Water for analytical laboratory use - EN ISO 3696 1995
Specification and test methods
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SIST EN ISO 9831:2004
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SIST EN ISO 9831:2004
INTERNATIONAL ISO
STANDARD 9831
First edition
1998-08-01
Animal feeding stuffs, animal products, and
faeces or urine — Determination of gross
calorific value — Bomb calorimeter method
Aliments des animaux, produits d'origine animale et excréments ou
urines — Détermination de la valeur calorifique brute — Méthode à la
bombe calorimétrique
A
Reference number
ISO 9831:1998(E)
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ISO 9831:1998(E)
Contents
1 Scope. 1
Normative references .
2 1
3 Definitions . 2
4 Principle . 2
5 Reagents and materials. 2
6 Apparatus . 3
7 Sampling. 4
8 Preparation of test sample and test portion. 4
9 Procedure . 5
10 Corrections . 7
11 Expression of results . 9
12 Precision . 10
13 Test report . 11
Annex A (normative) Determination of the effective heat capacity of
the calorimeter . 12
Annex B (normative) Special procedures for preparation of the test
sample . 14
Annex C (informative) Method of checking that the average deviation
of the rate of change of temperature is within the specified limit . 16
Annex D (informative) Examples of calculating the results of calorific
determinations . 18
Annex E (informative) Results of interlaboratory tests. 22
Annex F (informative) Bibliography. 23
© ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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ISO ISO 9831:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national standards bodies (ISO member bodies). The work of
preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. ISO collab-
orates closely with the International Electrotechnical Commission (IEC) on
all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 9831 was prepared by Technical Committee
ISO/TC 34, Agricultural food products, Subcommittee SC 10, Animal
feeding stuffs.
Annexes A and B are an integral part of this International Standard.
Annexes C to F are for information only.
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SIST EN ISO 9831:2004
©
INTERNATIONAL STANDARD ISO ISO 9831:1998(E)
Animal feeding stuffs, animal products, and faeces or urine —
Determination of gross calorific value — Bomb calorimeter method
1 Scope
This International Standard specifies a method for the determination of the gross calorific value of animal feeding
stuffs, animal products and faeces or urine at constant volume in an adiabatic, an isothermal, or a static bomb
calorimeter.
The result obtained by this method is the gross calorific value of the test sample at constant volume, the water of
the combustion products being condensed to liquid at the calorimeter temperature.
NOTE The international reference temperature for thermochemistry of 25 °C is used as the reference temperature for calorific
value, although the temperature dependence of the calorific value of the materials to which this International Standard applies
21 21
is small (about 1 J·g ·K ).
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 651:1975, Solid-stem calorimeter thermometers.
ISO 652:1975, Enclosed-scale calorimeter thermometers.
ISO 1770:1981, Solid-stem general purpose thermometers.
ISO 1771:1981, Enclosed-scale general purpose thermometers.
ISO 1928:1995, Solid mineral fuels — Determination of gross calorific value by the bomb calorimeter method, and
calculation of net calorific value.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods.
1)
ISO 6496:— , Animal feeding stuffs — Determination of moisture and volatile matter content.
2)
ISO 6498:— , Animal feeding stuffs — Preparation of test samples.
1) To be published. (Revision of ISO 6496:1983)
2) To be published. (Revision of ISO 6498:1983)
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3 Definitions
For the purposes of this International Standard, the definitions given in ISO 1928 apply.
4 Principle
Combustion of a weighed portion of the test sample in oxygen in a bomb calorimeter under standardized conditions.
Calculation of the gross calorific value from the temperature rise of the water in the calorimeter vessel and the mean
effective heat capacity of the calorimeter. Allowances are made for the heat released by the ignition fuse, for
thermochemical corrections and, where appropriate, for heat losses from the calorimeter to the water jacket.
5 Reagents and materials
Use only reagents of recognized analytical grade.
5.1 Water, complying with at least grade 3 in accordance with ISO 3696.
5.2 Oxygen, at a pressure capable of filling the bomb to 3 MPa and free from combustible matter.
NOTE 1 Oxygen manufactured by an electrolytic process may contain up to 4 % of hydrogen and is therefore unsuitable.
2
NOTE 2 1 MPa = 1 MN/m .
5.3 Fuse, comprising the following.
5.3.1 Firing wire, nickel/chromium wire (0,16 mm to 0,20 mm in diameter), or platinum wire (0,06 mm to 0,10 mm
in diameter).
5.3.2 Cotton thread, white cellulose.
5.3.3 Polyethylene strip, thin film of dimensions 30 mm by 5 mm.
5.4 Polyethylene bags, of dimensions 68 mm by 110 mm.
, of dimensions 50 mm by 55 mm, and mass approximately 170 mg.
5.5 Polyethylene bags
5.6 Silica gel, chromatographic-grade powder.
5.7 Sodium hydroxide solution, standard volumetric solution, c(NaOH) = 0,1 mol/l.
5.8 Screened methyl orange indicator solution, r = 1 g/l.
Dissolve 0,25 g of methyl orange and 0,15 g of xylene cyanol FF in 50 ml of 95 % (V/V) ethanol and dilute to 250 ml
with water.
5.9 Benzoic acid, thermochemical standard, certified by a national testing authority.
Drying or any treatment other than pelleting shall not be carried out.
The gross calorific value at constant volume of the benzoic acid, listed in the certificate for the conditions of use,
shall be adopted in calculating the effective heat capacity of the calorimeter (see annex A).
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6 Apparatus
Usual laboratory apparatus and, in particular, the following.
, capable of withstanding safely the pressure developed during combustion.
6.1 Bomb
The design shall permit complete recovery of all liquid products.
The construction materials shall resist corrosion by the acids produced by the combustion.
CAUTION — Inspect bomb parts regularly for wear and corrosion. Pay particular attention to the condition
of the threads of the main closure.
6.2 Calorimeter vessel, made of metal, highly polished on the outside and capable of holding sufficient water to
cover completely the flat upper surface of the bomb while the water is being stirred.
The vessel shall be provided with a console to centre the bomb in the vessel and to obtain water circulation below
the bomb.
6.3 Stirrer, driven at a constant rotational speed.
The stirrer shaft shall contain a non-conducting section below the cover of the water jacket to minimize the
transmission of heat to or from the system. If a cover is used for the calorimeter vessel, the non-conducting section
shall be above this cover.
For isothermal and static bomb calorimeters, the rate of stirring shall ensure that the length of the main period
(see 9.6) in determinations of effective heat capacity using benzoic acid (see annex A) does not exceed 10 min.
6.4 Water jacket, which may be an adiabatic, isothermal or static type, enclosing the calorimeter vessel with an
air-gap of approximately 10 mm separating the vessel and water jacket.
The adiabatic water jacket shall have either electrode or immersion heaters capable of supplying energy at a rate
sufficient to maintain the temperature of the water in the jacket to within 0,1 °C of that of the calorimeter vessel after
the charge has been fired. When in equilibrium at 25 °C, the temperature drift of the calorimeter vessel shall not
exceed 0,000 5 °C/min.
NOTE 1 Special precautions are needed at high environmental temperatures.
The isothermal water jacket shall be provided with a means of maintaining it at a constant temperature to the
nearest 0,1 °C.
The static water jacket shall have a thermal capacity great enough to restrict changes of temperature of the water in
it. From the time of firing the charge to the end of the after-period or during a period of 15 min, whichever is the
21
greater, with a cooling factor d = 0,002 0 min (see 10.3), the rise in temperature of the water in the jacket shall be
21
less than 0,16 °C; with a cooling factor d = 0,003 0 min , the rise in temperature shall be less than 0,11 °C.
NOTE 2 For an insulated metal jacket, this can be ensured by making the capacity at least 12,5 l, contained in a wide annular
jacket.
6.5 Temperature-measuring instrument, capable of indicating temperatures which, when corrected, have an
accuracy of 0,002 °C, so that temperature intervals of 2 °C to 3 °C can be determined with an accuracy of 0,004 °C.
It shall be calibrated against a known standard by a national testing authority, at intervals not larger than 0,5 °C over
the range of use or, for mercury-in-glass thermometers, over the whole graduated scale.
The following types of thermometer are suitable:
a) resistance thermometers comprising a platinum resistance, resistance bridge and galvanometer;
b) mercury-in-glass thermometers which conform to ISO 651, ISO 652, ISO 1770 or ISO 1771.
A viewer with a magnification of about five times is required for reading the temperature to the required accuracy.
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A mechanical vibrator is recommended to tap the thermometer for a period of about 10 s before reading the
temperature, to prevent sticking of the mercury column. If this is not available, the thermometer shall be tapped
manually, for example with a pencil.
6.6 Crucible, of silica, nickel/chromium or platinum.
The crucible shall be about 25 mm in diameter, flat-based and not more than 20 mm high. Silica crucibles shall be
about 1,5 mm thick and metal crucibles about 0,5 mm thick.
For benzoic acid, either of the crucibles specified is suitable. If, after combustion, smears or unburned material
occur on the crucible, a small nickel/chromium crucible (for example 0,25 mm thick, 15 mm in diameter and 7 mm
high) may be used.
6.7 Ignition circuit.
The electrical supply shall be 6 V to 12 V alternating current from a step-down transformer or direct current from
batteries. It is desirable to include a current-meter or pilot light in the circuit to indicate when current is flowing.
The firing switch shall be of the spring-loaded, normally open type.
6.8 Ancillary equipment, comprising the following.
6.8.1 Balance, capable of weighing at least 3 kg to the nearest 1 g.
6.8.2 Analytical balance, capable of weighing to the nearest 0,1 mg.
6.8.3 Briquette press.
6.8.4 Pressure regulator, to control the filling of the bomb with oxygen.
6.8.5 Pressure gauge, range from 0 MPa to 5 MPa, to indicate the pressure in the bomb.
6.8.6 Relief valve or bursting disc, operating at 3,5 MPa, installed in the filling line, to prevent overfilling the
bomb.
CAUTION — Equipment for high-pressure oxygen shall be kept free from oil and grease. Do not test or
calibrate the pressure gauge with hydrocarbon fluid.
6.9 Timer, fitted in a convenient place, indicating minutes and seconds.
It may usefully incorporate a device giving audible signals lasting 10 s starting at 1-min intervals.
7 Sampling
Sampling is not part of the method specified in this International Standard. A recommended sampling method is
given in ISO 6497 [4].
It is important that the laboratory receive a sample which is truly representative and has not been damaged or
changed during transport or storage.
8 Preparation of test sample and test portion
Prepare the test sample in accordance with ISO 6498.
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8.1 Air-dry samples
8.1.1 Grind the laboratory sample so that it passes completely through a sieve with 1 mm apertures.
Mix the sample, preferably by mechanical means, immediately before the determination. By use of the briquette
press (6.8.3), press 0,5 g to 5 g of the test sample to form a pellet. The mass of the test portion depends on the
calorific value and the effective heat capacity of the calorimeter. The mass of the test portion should be such that
the temperature rise due to combustion is between 2 °C and 3 °C.
Adequate precautions shall be taken to prevent uptake or loss of moisture by the test sample during mixing and
pelletizing, so that the moisture content of the test sample, recently determined as specified in 9.2, can be used in
further calculations. If this is not possible, the sample shall be exposed in a thin layer for the minimum time
necessary for the moisture content to reach approximate equilibrium with the atmosphere of the laboratory
containing the bomb calorimeter.
8.1.2 For air-dry samples with a fat content exceeding 10 % (m/m), and for air-dry samples which cannot be
pelleted easily, proceed as specified in B.1.
8.2 Liquid samples
Proceed as specified in B.2.
8.3 Samples of fresh materials
Proceed as specified in B.3.
9 Procedure
9.1 Determination of effective heat capacity of the calorimeter
If the effective heat capacity of the calorimeter is not known, or if the known value is questioned, and at intervals not
exceeding 6 months, determine the effective heat capacity of the calorimeter as specified in annex A.
9.2 Determination of moisture content
For air-dry samples, determine the moisture content of the test sample in accordance with ISO 6496, at the same
time as the determination of the calorific value.
9.3 Preparation of the bomb
Place the test portion (clause 8) in the form of a pellet (see 8.1.1) or contained in a polyethylene bag (see 8.1.2, 8.2
and 8.3), weighed to the nearest 0,1 mg, in the crucible (6.6) of the bomb.
NOTE 1 Normally 1 g of air-dry sample is an appropriate test portion (see also clause 8).
Connect a piece of firing wire (5.3.1) tautly across the terminals of the bomb. Tie a cotton thread (5.3.2) or a strip of
polyethylene film (5.3.3), of known mass, to the firing wire. Arrange the ends of the cotton thread or polyethylene
film so that they touch the sample.
NOTE 2 For convenience, a measured length of cotton thread of known mass per length may be used. The length used in
each determination of calorific value should be the same as was used in the determination of the effective heat capacity of the
calorimeter. The same applies to the polyethylene strip, if used.
Put 5 ml of water in the bomb (6.1). Assemble the bomb and charge it slowly with oxygen (5.2) to a pressure of
3 MPa without displacing the original air. If the bomb is inadvertently charged with oxygen above 3,3 MPa, discard
the test and begin again.
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9.4 Preparation of the calorimeter vessel
Put sufficient water in the calorimeter vessel (6.2) to cover the flat upper surface of the bomb cap. This quantity of
water shall be the same, to within 1 g, as that used in the determination of the mean effective heat capacity of the
calorimeter (9.1).
If an isothermal calorimeter or static calorimeter is used, the initial temperature of the water shall be such that, at the
end of the main period [see 9.6 b)], the temperature does not exceed that of the water in the jacket by more than
0,5 °C.
Transfer the calorimeter vessel to the water jacket (6.4). Lower the bomb into the calorimeter vessel and check that
the bomb is gas-tight. If gas escapes from the bomb, discard the test, eliminate the cause of leakage and begin
again.
For an adiabatic calorimeter, proceed in accordance with 9.5.
For isothermal and static calorimeters, proceed in accordance with 9.6.
9.5 Procedure specific for an adiabatic calorimeter
Assemble and start up the apparatus. Use a constant rate of stirring, so that the predetermined interval (see A.4)
does not exceed 10 min. Select the setting of the bridge circuit that will result in the minimum drift in temperature of
the calorimeter vessel at the final temperature.
After 10 min, tap the thermometer (see 6.5) lightly and read it to 0,001 °C. This is the firing temperature (t ). Fire the
0
charge, holding the switch closed only long enough to ignite the fuse.
CAUTION — Do not extend any part of the body over the calorimeter during firing, nor for 20 s thereafter.
After the predetermined interval, established in the determination (9.1) of the effective heat capacity of the
calorimeter, tap the thermometer again and read it to 0,001 °C. This is the final temperature (t ). The observer
n
shall take care to avoid parallax errors when using the magnifying viewer (see 6.5) to read mercury-in-glass
thermometers.
Proceed in accordance with 9.7.
9.6 Procedure specific for isothermal and static calorimeters
Assemble the apparatus. Start the stirrer and maintain in operation at a constant rate throughout the determination.
Stir for at least 10 min before starting to read the temperature to 0,001 °C and continue to do so at intervals of 1 min
for a period of 5 min.
Tap the thermometer (see 6.5) lightly for 10 s before each reading. Take care to avoid parallax errors when using
the magnifying viewer (see 6.5) to read mercury-in-glass thermometers.
Fire the charge immediately after reading the last temperature in the preliminary period [see a) below]. Hold the
switch closed only long enough to ignite the fuse.
CAUTION — Do not extend any part of the body over the calorimeter during firing, nor for 20 s thereafter.
Read the thermometer as follows.
a) Preliminary period: If the average deviation of the values of the rate of change of temperature during this
period of 5 min exceeds 0,001 °C/min (see note 2), continue to read the thermometer at 1-min intervals until the
average deviation is less than 0,001 °C/min for a period of 5 min. The last temperature of the preliminary period
is the initial temperature (t ) of the main period.
0
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b) Main period: During the first few minutes of the main period, it will not be possible to read the thermometer to
0,001 °C, but resume readings to this precision as soon as possible and continue them to the end of the test.
The main period does not necessarily end with the attainment of maximum temperature. The last temperature
of the main period is the final temperature (t ), which is the initial temperature of the after-period.
n
c) This period begins at the first temperature after which for a subsequent 5-min period, the
After-period:
average deviation of the individual values of the rate of change of temperature is not more than 0,001 °C/min
(see note 2). This first temperature is the final temperature (t ).
n
NOTE 1 If the Regnault-Pfaundler cooling correction (see 10.3) is to be calculated, the procedure specified should be
adopted. If an alternative formula, which is equivalent and acceptable, is to be used, some of the temperature readings may not
be required and the procedure should be modified accordingly.
NOTE 2 A convenient method of checking that the average deviation of the rate of change of temperature during the
preliminary period and the after-period is within the specified limit is specified in annex C.
9.7 Assesment of the bomb contents
9.7.1 Remove the bomb from the calorimeter vessel, release the pressure and dismantle the bomb. Examine the
bomb interior and discontinue the test if unburned sample or a sooty deposit is visible.
9.7.2 When certain samples are tested, the residue in the bomb may contain detectable unburned sample. A
correction to be applied for such persistently incomplete combustion may be calculated from the amount of
unburned carbon, which may be estimated by the procedure described in 9.7.3.
9.7.3 The mass of unburned carbon in the crucible may be estimated as follows.
Transfer the contents of the crucible (not the lining) to a silica or porcelain dish and dry for 1 h at 105 °C. Leave to
cool, then weigh the dish and its contents to the nearest 0,1 mg. Heat at 550 °C for 1 h. Leave to cool and reweigh
to determine the loss in mass. The loss is taken to be unburned carbon.
Alternatively, the unburned carbon may be determined by one of the methods specified in ISO 609 [1] or
ISO 625 [2]. Should more than 6 mg of unburned carbon be determined, the correction will be invalid and the
determination of gross calorific value should be repeated.
9.8 Determination of acidity
Wash the contents of the bomb into a beaker with water. Wash the underside of the bomb cap and the outside of
the crucible with water. Add the washings to the beaker. Dilute to approximately 100 ml and boil to expel carbon
dioxide.
While the mixture is still hot, titrate the warm (not boiling) bomb washings with sodium hydroxide solution (5.7) using
the screened methyl orange solution (5.8) as indicator, to determine the total acidity.
10 Corrections
10.1 General
Apply the corrections given in 10.2 to 10.6 to the experimental observations.
10.2 Thermometer corrections
If a mercury-in-glass thermometer is used, apply the corrections specified in the certificate issued with the
thermometer, to the observed firing temperature (t ) and to the final temperature (t ).
0 n
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10.3 Cooling correction
For an adiabatic calorimeter such as is
...
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