Characterisation of waste - Leaching behaviour test - Determination of the reducing character and the reducing capacity

This European Standard describes three laboratory tests to determine the reducing character and the reducing capacity of building and waste materials or their eluates.
For a specification of the materials with which experience has been acquired with the execution of the tests according to this European Standard please refer to Annex A and [1].
NOTE   Materials with reducing properties can in practice under both oxidising and anoxic (isolated) conditions show completely different leaching behaviour than with the leaching tests specified in prEN 16457. This may seriously hamper the interpretation of the leaching tests specified in the supporting CEN/TR on content and leaching (under development).

Charakterisierung von Abfällen - Auslaugungsverhalten - Bestimmung der Reduktionseigenschaft und der Reduktionsfähigkeit

Diese Technische Spezifikation legt drei Laborprüfungen zur Bestimmung der Reduktionseigenschaft und der Reduktionsfähigkeit von Bauprodukten, Abfallmaterialen und der Eluate, die durch Kontakt mit diesen Feststoffen entstehen, fest. Die von dem Produkt freigesetzten reduzierenden Spezies werden titriert, um die Reduktionsfähigkeit zu quantifizieren.
Für die Präzisierung der Materialien, mit denen Erfahrungen bei der Durchführung der Prüfungen nach dieser Technischen Spezifikation gesammelt wurden, wird auf Anhang A und [16] hingewiesen.
ANMERKUNG   Materialien mit reduzierenden Eigenschaften können in der Praxis sowohl unter oxidierenden als auch unter sauerstofffreien Bedingungen (unter Ausschluss von Sauerstoff) ein vollständig unterschiedliches Elutionsverhalten zeigen, als es mit den Elutionsversuchen in EN 16457 erhalten wird. Das kann die Interpretation der Elutionsversuche ernsthaft behindern, wenn diese Bedingung nicht berücksichtigt wird.

Caractérisation des déchets - Essais de comportement à la lixiviation - Détermination des propriétés réductrices et de la capacité de réduction

La présente Spécification technique décrit trois essais en laboratoire permettant de déterminer les propriétés réductrices et la capacité de réduction des produits de construction, des déchets et de l'éluat résultant de l'exposition de ces solides à un lixiviant. Les espèces réductrices libérées par le produit sont dosées par titrage afin de quantifier la capacité de réduction.
Pour une spécification des matériaux pour lesquels une expérience a été acquise dans l'exécution des essais conformes à la présente Spécification technique, se reporter à l'Annexe A et à la référence [15].
NOTE   Dans la pratique, les matériaux ayant des propriétés réductrices peuvent, dans des conditions oxydantes et anoxiques (isolées), présenter un comportement à la lixiviation différent de celui obtenu avec les essais de lixiviation spécifiés dans l'EN 16457. Cela peut sérieusement gêner l'interprétation des essais de lixiviation, si cette condition n'est pas prise en considération.

Karakterizacija odpadkov - Izluževalni preskus - Ugotavljanje redukcijske sposobnosti in zmogljivosti

General Information

Status
Published
Public Enquiry End Date
19-Nov-2013
Publication Date
08-Jun-2015
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
25-May-2015
Due Date
30-Jul-2015
Completion Date
09-Jun-2015

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Karakterizacija odpadkov - Izluževalni preskus - Ugotavljanje redukcijske sposobnosti in zmogljivostiCharakterisierung von Abfällen - Auslaugungsverhalten - Bestimmung der Reduktionseigenschaft und der ReduktionsfähigkeitCaractérisation des déchets - Essais de comportement à la lixiviation - Détermination des propriétés réductrices et de la capacité de réductionCharacterisation of waste - Leaching behaviour test - Determination of the reducing character and the reducing capacity13.030.01Odpadki na splošnoWastes in generalICS:Ta slovenski standard je istoveten z:CEN/TS 16660:2015SIST EN 16660:2015en,fr,de01-julij-2015SIST EN 16660:2015SLOVENSKI

STANDARD
SIST EN 16660:2015
TECHNICAL SPECIFICATION SPÉCIFICATION TECHNIQUE TECHNISCHE SPEZIFIKATION
CEN/TS 16660
May 2015 ICS 13.030.01 English Version

Characterization of waste - Leaching behaviour test - Determination of the reducing character and the reducing capacity

Caractérisation des déchets - Essais de comportement à la lixiviation - Détermination des propriétés réductrices et de la capacité de réduction

Charakterisierung von Abfällen - Untersuchung des Elutionsverhaltens - Bestimmung der Reduktionseigenschaft und der Reduktionsfähigkeit This Technical Specification (CEN/TS) was approved by CEN on 21 March 2015 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,

B-1000 Brussels © 2015 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TS 16660:2015 ESIST EN 16660:2015

CEN/TS 16660:2015 (E) 2 Contents Page

Foreword ..............................................................................................................................................................3 Introduction .........................................................................................................................................................4 1 Scope ......................................................................................................................................................6 2 Normative references ............................................................................................................................6 3 Terms and definitions ...........................................................................................................................6 4 Principle ..................................................................................................................................................7 5 Preparation of the test portion .............................................................................................................8 6 Reagents .................................................................................................................................................9 7 Equipment ..............................................................................................................................................9 8 Procedure ............................................................................................................................................ 10 8.1 General ................................................................................................................................................. 10 8.2 Determination of the reducing character ......................................................................................... 10 8.3 Determination of the reducing capacity of the solid material ........................................................ 11 8.3.1 Calibration procedure ........................................................................................................................ 11 8.3.2 Determination of the reducing capacity of the solid material ........................................................ 11 8.4 Determination of the reducing capacity of the eluates ................................................................... 12 8.4.1 Calibration procedure ........................................................................................................................ 12 8.4.2 Determination of the reducing capacity of the eluates ................................................................... 12 9 Calculations ......................................................................................................................................... 13 9.1 Determination of the reducing character ......................................................................................... 13 9.2 Calculation of the reducing capacity of the solid material ............................................................. 13 9.3 Calculation of the reducing capacity of the eluates ........................................................................ 14 10 Test report ........................................................................................................................................... 15 Annex A (informative)

Validation of the provisions of the reducing capacity ........................................... 16 A.1 General ................................................................................................................................................. 16 A.2 Validation results 9.1 'Determination of the reducing character' .................................................. 16 A.3 Validation results 9.2 'Calculation of the reducing capacity of the solid material' ...................... 17 A.4 Validation results 9.3 'Calculation of the reducing capacity of the eluates' ................................. 18 Annex B (informative)

Explanatory note ........................................................................................................ 19 B.1 Cause of reducing material behaviour ............................................................................................. 19 B.2 Set-up of the tests to determine the reducing capacity.................................................................. 19 B.3 Limitations of the cerimetric determination method ....................................................................... 20 B.4 Materials with reducing properties ................................................................................................... 20 Annex C (informative)

Sampling, storage and pretreatment ....................................................................... 22 Bibliography ..................................................................................................................................................... 23

SIST EN 16660:2015

CEN/TS 16660:2015 (E) 3 Foreword This document (CEN/TS 16660:2015) has been prepared by Technical Committee CEN/TC 292 “Characterization of waste”, the secretariat of which is held by NEN. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document has been developed primarily to support the requirements for leaching behaviour testing within EU and EFTA countries. This document was elaborated on the basis of NEN 7348:2006. To determine the various aspects of the leaching behaviour (the leaching characteristics) of solid earthy and stony building and waste materials a series of steps should be followed, in particular sampling, sample pretreatment, characterization tests, digestion and chemical analysis of the solid substance or the eluates. An umbrella standard (EN 16457) is developed that gives general instructions. In here the relationship is given between all the standards in each step, each with a specific scope. To determine the leaching characteristics, the general instructions or the specific standards to which reference is made shall be followed with good consistency. This Technical Specification describes a test that can be used to determine whether or not the material to be tested possesses reducing properties. If this is the case, a next test is used to quantify the reducing capacity of this material or its eluates. Based on the results of this Technical Specification, it can be established whether leaching under practical conditions can differ (considerably) from leaching under standard aerobic laboratory conditions and whether there is justification for testing leaching under low-oxygen conditions (see Annex A, [16]). The standards that characterize the various aspects of the leaching behaviour are produced and published in phases. This means that upon the publication of this Technical Specification, reference is not yet made in all relevant standards. For the missing aspects, users of this Technical Specification will have to make their own choice of the methods to be used. Annex A gives information on the validation and materials used. Annex B gives a further explanatory note on the reducing capacity. In addition to specifications provided in EN 15002, Annex C gives further guidance on sampling, sample pretreatment and sample storage. For more information, the standards and other publications included in the bibliography that have been published in this respect can be used. The numbered clauses are normative with the exception of the passages marked with the heading 'NOTE'; the annexes are informative. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 16660:2015

CEN/TS 16660:2015 (E) 4 Introduction This document specifies a set of three tests to assess if a material has reducing properties and subsequently to determine the reducing capacity of that material and the reducing capacity of an eluate produced at low liquid to solid ratio. For a proper performance special attention is given to minimize contact with the atmosphere before and during testing. For the complete characterization of the leaching behaviour of waste under specified conditions the application of other test methods is required (see EN 12920). Anyone dealing with waste and sludge analysis should be aware of the typical risks of that kind of material irrespective of the parameter to be determined. Waste and sludge samples can contain hazardous (e.g. toxic, reactive, flammable, infectious) substances, which can be liable to biological and/or chemical reaction. Consequently these samples should be handled with special care. Gases which can be produced by microbiological or chemical activity are potentially flammable and will pressurize sealed bottles. Bursting bottles are likely to result in hazardous shrapnel, dust and/or aerosol. National regulations should be followed with respect to all hazards associated with this method. In the different European countries, tests have been developed to characterize and assess the constituents which can be leached from waste materials. The release of soluble constituents upon contact with water is regarded as one of the main mechanism of release which results in a potential risk to the environment during life-cycle of waste materials (disposal or re-use scenario). The intent of these tests is to identify the leaching properties of waste materials. The complexity of the leaching process makes simplifications necessary. Not all of the relevant aspects of leaching behaviour can be addressed in one single standard. This Technical Specification addresses reducing properties of materials and the consequences to the test or test conditions to be applied in performing leaching tests. Procedures to characterize the behaviour of waste materials can generally be divided into three steps, using different tests in relation to the objective. The following test hierarchy is taken from the Landfill Directive1) and the Decision on Annex II of this Directive2) for disposal of waste. a) Basic characterization constitutes a full characterization of the waste by gathering all the necessary information for a safe management of the waste in the short and long term. Basic characterization may provide information on the waste (type and origin, composition, consistency, leachability, etc.), information for understanding the behaviour of waste in the considered management scenario, comparison of waste properties against limit values, and detection of key variables (critical parameters as liquid/solid (L/S) ratios, leachant composition, factors controlling leachability such as pH, redox potential, complexing capacity and physical parameters) for compliance testing and options for simplification of compliance testing. Characterization may deliver ratios between test results from basic characterization and results from simplified test procedures as well as information on a suitable frequency for compliance testing. In addition to the leaching behaviour, the composition of the waste should be known or determined by testing. The tests used for basic characterization should always include those to be used for compliance testing. b) Compliance testing is used to demonstrate that the sample of today fits the population of samples tested before by basic characterization and through that, is used to carry out compliance with regulatory limit values. The compliance test should therefore always be part of the basic characterization program. The compliance test focuses on key variables and leaching behaviour identified by basic characterization tests. Parts of basic characterization tests can also be used for compliance purposes.

1) Council Directive 1999/31/EC of 26 April 1999 on the landfill of waste. 2) Council Decision 2003/33/EC of 19 December 2002. SIST EN 16660:2015

CEN/TS 16660:2015 (E) 5 c) On-site verification tests are used as a rapid check to confirm that the waste is the same as that which has been subjected to characterization or compliance tests. On-site verification tests are not necessarily leaching tests. The test procedure described in this document is a basic characterization test and falls in category a). SIST EN 16660:2015

CEN/TS 16660:2015 (E) 6 1 Scope This Technical Specification specifies three laboratory tests to determine the reducing character and the reducing capacity of construction products, waste materials and the eluate resulting from exposure of these solids to a leachant. Reducing species released from the product are titrated to quantify the reducing capacity. For a specification of the materials with which experience has been acquired with the execution of the tests according to this Technical Specification see Annex A and [16]. NOTE Materials with reducing properties can in practice under both oxidizing and anoxic (isolated) conditions show completely different leaching behaviour than obtained with the leaching tests specified in EN 16457. This may seriously hamper the interpretation of the leaching tests, if this condition is not taken into consideration. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 14346, Characterization of waste - Calculation of dry matter by determination of dry residue or water content EN 15002, Characterization of waste - Preparation of test portions from the laboratory sample EN ISO 10523, Water quality - Determination of pH (ISO 10523) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. Additional terms and definitions are given in EN 13965-2. 3.1 eluate solution obtained by a leaching test 3.2 laboratory sample sample or sub-sample(s) sent to or received by the laboratory [SOURCE: IUPAC, 1990] Note 1 to entry: When the laboratory sample is further prepared (reduced) by subdividing, cutting, sawing, coring, or by combinations of these operations, the result is the test sample. When no preparation of the laboratory sample is required, the laboratory sample is the test sample. A test portion is removed from the test sample for the performance of the test or for analysis. The laboratory sample is the final sample from the point of view of sampling but it is the initial sample from the point of view of the laboratory. Note 2 to entry: Several laboratory samples may be prepared and sent to different laboratories or to the same laboratory for different purposes. When sent to the same laboratory, the set is generally considered as a single laboratory sample and is documented as a single sample. SIST EN 16660:2015

CEN/TS 16660:2015 (E) 7 3.3 leaching test test during which a material is put into contact with a leachant and some constituents of the material are extracted [SOURCE: EN 12457-1:2002] 3.4 liquid to solid-ratio L/S ratio between the amount of liquid (L) and of solid (S) in the test Note 1 to entry: L/S is expressed in l/kg dry matter. 3.5 reducing capacity potential for a material to impose reducing conditions Note 1 to entry: Reducing capacity is expressed in mmol O2/kg. 3.6 redox potential value that indicates reducing or oxidized state of a material Note 1 to entry: Redox potential is expressed in mV. 3.7 sample portion of material selected from a larger quantity of material 3.8 test portion amount or volume of the test sample taken for analysis, usually of known weight or volume [SOURCE: IUPAC, 1990] 3.9 test sample sample, prepared from the laboratory sample, from which test portions are removed for testing or for analysis [SOURCE: IUPAC, 1990] 4 Principle The purpose of the tests described in this Technical Specification is to: — establish whether or not a material has reducing properties; — establish where necessary the reducing capacity of this material or its eluates in quantitative terms. The reducing character of a material is determined by bringing the material into contact with demineralized water at a low L/S value in an airtight sealed vessel (24 h contact time) and then measuring the redox potential with respect to the redox potential in water with the same pH. SIST EN 16660:2015

CEN/TS 16660:2015 (E) 8 The reducing capacity of a material or its eluates is determined by carrying out a redox titration. In the titration an excess Ce(IV) is used to oxidize the reducing components. Then by back titration the oxidant demand is determined. NOTE Sulphide is often the major reducing component. 5 Preparation of the test portion The test consists of three parts which in principle can be carried out separately. For the single execution of the test to determine the reducing character according to this Technical Specification (8.2) a test portion A1 of (50 ± 5) g dry matter is necessary, of which the dry matter content wdm is known and of which at least a mass percentage of 95 % (dry matter) of the particles is smaller than 4 mm. For the single execution of the test to determine the reducing capacity of the solid material according to this Technical Specification (8.3) a test portion A2 of (2 ± 0,002) g dry matter is necessary, of which the dry matter content wdm is known and of which at least a mass percentage of 95 % (dry matter) of the particles is smaller than 125

For the single execution of the test to determine the reducing capacity of the eluates according to this Technical Specification (8.4) a test portion A3 of (20 ± 0,02) g dry matter is necessary, of which the dry matter content wdm is known and of which at least a mass percentage of 95 % (dry matter) of the particles is smaller than 4 mm. The dry residue of the sample shall be determined from a subsample which is dried at 105 °C ± 3 °C according to EN 14346. The dry residue expressed as a percentage of the mass fraction is calculated as follows: rddr100mmw×= (1) where wdr is the dry residue of the sample, expressed as percentage (%); md is the mass after drying, in grams (g); mr is the mass before drying, in grams (g). Calculate the undried mass of the test portion Mw in grams to be used for the test as follows: dwdr100MMW=×

(2) where Mw is the total mass of the test portion, in grams (g); Md is the dry mass of the test portion, in grams (g); wdr is the dry residue of the sample, expressed as percentage (%). SIST EN 16660:2015

CEN/TS 16660:2015 (E) 9 For the sampling of solid earthy and stony building and waste materials for leaching tests no standards are yet available that are aimed at preserving the reducing capacity of the material to be tested. It is recommended to use the procedures described in EN 14899, taking into account the instructions to limit contact with the outside air (see Annex C). If the sample from which the test portions are obtained has to undergo pretreatment, use the procedures described in EN 15002, taking into account the instructions to limit contact with the outside air as much as technically feasible (see Annex C). 6 Reagents Use only reagents of recognized analytical grade, unless otherwise specified. 6.1 Demineralized water, with a conductivity of max. 1 mS/cm. 6.2 Hydrochloric acid, c(HCl) = (1 ± 0,1) mol/l. 6.3 Sulphuric acid, c(H2SO4) = (1 ± 0,01) mol/l. 6.4 Sodium hydroxide solution, c(NaOH) = (1 ± 0,1) mol/l. 6.5 Cerium(IV) sulphate solution, c(Ce(SO4)2) = (0,1 ± 0,001) mol/l in (1 ± 0,01) mol/l sulphuric acid. 6.6 Iron(II) sulphate solution, c(FeSO4) = (0,1 ± 0,001) mol/l in (0,1 ± 0,001) mol/l sulphuric acid. 6.7 Standard redox solutions, suitable for the calibration of a redox electrode, with an inaccuracy of max. 1 mV. NOTE A buffer solution with EH = 439 mV (Emeas = 220 mV) and pH 7 will usually suffice. 6.8 Nitrogen gas, N2, of a purity of 99,999 %, O2 contamination < 3 ppm. It shall be possible to supply the nitrogen gas as a constant stream. NOTE Argon gas can be used instead of nitrogen gas also. The use of nitrogen gas is more cost effective and therefore prescribed in this Technical Specification. 7 Equipment Check the equipment and requisites listed below before use for proper operation and absence of disrupting elements that may affect the result of the test. Calibrate and/or check the equipment listed under 7.1, 7.2, 7.5, 7.9 and 7.10 before use. 7.1 EH electrode with reference electrode, standard combination of an EH platinum electrode with a reference electrode of Ag/AgCl or calomel (Hg2Cl2). NOTE No standards are available for the calibration and measurement of the redox potential on a laboratory scale. The guidelines of the electrode manufacturer can be followed for this. 7.2 pH meter, with a measurement accuracy of at least ± 0,1 pH units and calibrated according to EN ISO 10523. 7.3 Erlenmeyer, sealable 100 ml glass Erlenmeyer or glass pot, with a neck that is wide enough to pass a pH electrode or EH electrode (7.1) through it. SIST EN 16660:2015

CEN/TS 16660:2015 (E) 10 7.4 Vibrating table, with a travel of at least 5 cm and orbital shaking motion. 7.5 Titration set-up with burette, titration set-up with burette, with an inaccuracy of max. 0,02 ml, and fitted with an electrode for measuring the redox potential via an mV read-out (7.1). 7.6 Filtering device, either a vacuum filtration device (between 30 kPa and 70 kPa) (300 mbar to 700 mbar) or a high-pressure filtration apparatus (<0,5 MPa) (5 bar). Rinsing is compulsory. NOTE An alternative is the use of vacuum filtration, provided a continuous stream of nitrogen gas (6.8) is passed over the solution to be filtered to prevent oxidation. 7.7 Membrane filters, for the filtration equipment (7.6) with a pore size of 0,45 µm that have been rinsed with demineralized water (6.1). 7.8 Prefilters, with a pore size of max. 1,5 µm. 7.9 Analytical balance, with a measurement range up to 300 g and an accuracy of at least 10 mg. 7.10 Analytical balance, with a measurement range up to 100 g and an accuracy of at least 0,1 mg. 7.11

Thermometer, for temperature measurement in air and liquid. 8 Procedure 8.1 General The reducing character and/or the reducing capacity of the material to be tested or its eluates shall be determined by respectively: — carrying out the test according to 8.2 for the reducing character; — carrying out the test according to 8.3 for the reducing capacity of the solid; — carrying out the test according to 8.4 for the reducing capacity of the eluates; — carrying out the calculations according to Clause 9. All tests shall be carried out at a temperature between 19 °C and 23 °C. 8.2 Determination of the reducing character De-aerate minimal 500 ml demineralized water (6.1) by bubbling nitrogen gas (6.8) through it for at least 18 h. Less than 18 h is also possible, provided the redox potential of the water does not change anymore. If the de-aerated water has to be stored, this should be done in gas-tight packaging. Weigh (50 ± 5) g (dry matter) of the available sample with an analytical balance (7.9) and place this in an Erlenmeyer (7.3). This is the test portion A1. Add to the Erlenmeyer containing the test portion (50 ± 5) ml of the de-aerated water. Drive the remaining air out of the Erlenmeyer by blowing nitrogen gas (6.8) over the solution for at least 1 min. After all remaining air is driven out seal the Erlenmeyer airtight and shake for 24 h (7.4). SIST EN 16660:2015

CEN/TS 16660:2015 (E) 11 Some samples may absorb a lot of moisture (for example dried sludge), which makes the execution of the test more difficult. In that case more than 50 ml of de-aerated water may be added. In this case a note shall be made in the test report stating that more than 50 ml of de-aerated water was added to the sample. If reducing conditions arise as a result of decomposition in the material (for example anaerobic breakdown of organic matter in materials containing a high amount of organic matter), a contact time of 24 h is possibly too short. If there are indications that such reactions can be significant, the contact time may be extended up to four weeks. A note should be made in the test report if the contact time was more than 24 h. Check the platinum electrode of the standard redox combination (7.1) against the standard redox solution (6.7). Then measure the redox potential of the solution produced in the Erlenmeyer after 24 h (Emeasured of the solution produced) with the platinum electrode while constantly blowing nitrogen gas (6.8) over it. Measure the pH of this solution with the pH meter (7.2) with an accuracy of 0,1 pH unit. Adjust the pH of a quantity of de-aerated water in an Erlenmeyer at the same pH (with an accuracy of 0,1 pH unit) as measured in the solution obtained after 24 h from the test portion A1, by adding a volume of hydrochloric acid (6.2) or sodium hydroxide (6.4). Then measure the redox potential of this water with the platinum electrode (Emeasured of the demineralized water) while constantly blowing nitrogen gas (6.8) over it. NOTE Particularly in the neutral pH range it is not easy to set the pH exactly with acid and base. In that case a titration of the water which spans the relevant pH range, can be carried out where the EH is measured for different pH values. By plotting the pH and EH data in a graph form, the corresponding EH can be determined for the desired pH. 8.3 Determination of the reducing capacity of the solid material 8.3.1 Calibration procedure Prepare fresh Ce(IV) sulphate solution (6.5) and Fe(II) sulphate solution (6.6). Calibrate/titrate the Fe(II) sulphate solution (6.6) against (10 ± 0,02) ml Ce(IV) sulphate solution (6.5). Register the volumes of used Fe(II) sulphate solution (VFe(II)) and Ce(IV) sulphate solution (VCe(IV)). The Fe(II) sulphate solution is subject to oxidation and should therefore be prepared shortly before the test. NOTE The solution can be kept sealed from the air for no more than a few days. The procedure described above serves to determine the strength of the Fe(II) solution prior to the test (MFe(II)). For the titration of 10 ml Ce(IV) solution approximately 10 ml Fe(II) sulphate solution will be necessary. 8.3.2 Determination of the reducing capacity of the solid material It may be that a slight pressure will build up in the Erlenmeyer during the equilibrium time as a result of gas formation. From a safety point of view the (glass) stoppers in the Erlenmeyers shall not be fixed too tightly. Weigh (2 ± 0,002) g (dry matter) (m0) of the available sample with an analytical balance (7.10

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