SIST EN ISO 1248:2009
(Main)Iron oxide pigments - Specifications and methods of test (ISO 1248:2006 including Technical Corrigendum 1:2007)
Iron oxide pigments - Specifications and methods of test (ISO 1248:2006 including Technical Corrigendum 1:2007)
This International Standard specifies the requirements and the corresponding methods of test for all manufactured and natural iron oxide pigments (except micaceous), including rapid dispersion pigments, in dry form, suitable for general use. These pigments are identified by Colour Index Nos. Red 101 and 102, Yellow 42 and 43, Brown 6 and 7, and Black 11. This International Standard does not cover micaceous iron oxide pigments, transparent iron oxide pigments, granular grey iron oxide and magnetic iron oxide pigments other than those of Colour Index Black 11.
Eisenoxid-Pigmente - Anforderungen und Prüfverfahren (ISO 1248:2006, einschließlich Technische Korrektur 1:2007)
Diese Internationale Norm legt die Anforderungen und die entsprechenden Prüfverfahren für alle synthetisch hergestellten und natürlichen Eisenoxid-Pigmente (ausgenommen Eisenglimmer-Pigmente), einschließlich schnell dispergierbarer Pigmente, in trockenem Zustand fest. Diese Pigmente sind zur allgemeinen Verwendung geeignet und durch die Colour Index-Nummern ) Rot 101 und 102, Gelb 42 und 43, Braun 6 und 7 sowie Schwarz 11 (siehe Tabelle 1) charakterisiert.
Diese Internationale Norm legt keine Anforderungen an Eisenglimmer-Pigmente fest (siehe Anmerkung 1). Sie schließt auch transparente Eisenoxid-Pigmente, graue Eisenoxide in Granulatform (siehe Anmerkung 2) sowie magnetische Eisenoxid-Pigmente mit Ausnahme von Colour Index Schwarz 11 aus.
ANMERKUNG 1 Die Anforderungen und die entsprechenden Prüfverfahren für Eisenglimmer-Pigmente sind in ISO 10601 enthalten.
ANMERKUNG 2 Graue Eisenoxide in Granulatform sind zu abrasiv für die allgemeine Verwendung.
Pigments à base d'oxydes de fer - Spécifications et méthodes d'essai (ISO 1248:2006 Corrigendum téchnique 1:2007 inclus)
L'ISO 1248:2006 spécifie les exigences et les méthodes d'essai correspondantes pour tous les pigments à base d'oxydes de fer artificiels et naturels, sous forme sèche, destinés à un usage général. Ces pigments sont identifiés par les numéros suivants du Colour Index: Red 101 et 102, Yellow 42 et 43, Brown 6 et 7 et Black 11, et comprennent les «pigments à dispersion rapide».
L'ISO 1248:2006 ne couvre pas les pigments à base d'oxydes de fer micacés, les pigments à base d'oxydes de fer transparents, les pigments à base d'oxydes de fer gris granuleux ou les pigments à base d'oxydes de fer magnétiques autres que ceux correspondant au pigment Black 11 du Colour Index.
Pigmenti železovega oksida - Specifikacije in metode preskušanja (ISO 1248:2006, vključno s tehničnim popravkom 1:2007)
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Eisenoxid-Pigmente - Anforderungen und Prüfverfahren (ISO 1248:2006, einschließlich Technische Korrektur 1:2007)Pigments à base d'oxydes de fer - Spécifications et méthodes d'essai (ISO 1248:2006 Corrigendum téchnique 1:2007 inclus)Iron oxide pigments - Specifications and methods of test (ISO 1248:2006 including Technical Corrigendum 1:2007)87.060.10Pigmenti in polnilaPigments and extendersICS:Ta slovenski standard je istoveten z:EN ISO 1248:2008SIST EN ISO 1248:2009en01-marec-2009SIST EN ISO 1248:2009SLOVENSKI
STANDARD
SIST EN ISO 1248:2009
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN ISO 1248March 2008ICS 87.060.10 English VersionIron oxide pigments - Specifications and methods of test (ISO1248:2006 including Technical Corrigendum 1:2007)Pigments à base d'oxydes de fer - Spécifications etméthodes d'essai (ISO 1248:2006 Corrigendum téchnique1:2007 inclus)Eisenoxid-Pigmente - Anforderungen und Prüfverfahren(ISO 1248:2006, einschließlich Technische Korrektur1:2007)This European Standard was approved by CEN on 28 February 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN 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 translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2008 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 1248:2008: ESIST EN ISO 1248:2009
EN ISO 1248:2008 (E) 2 Contents Page Foreword.3
SIST EN ISO 1248:2009
EN ISO 1248:2008 (E) 3 Foreword The text of ISO 1248:2006 including Technical Corrigendum 1:2007 has been prepared by Technical Committee ISO/TC 35 “Paints and varnishes” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 1248:2008 by Technical Committee CEN/TC 298 “Pigments and extenders” the secretariat of which is held by DIN. 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 September 2008, and conflicting national standards shall be withdrawn at the latest by September 2008. 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. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 1248:2006 including Technical Corrigendum 1:2007 has been approved by CEN as a EN ISO 1248:2008 without any modification.
SIST EN ISO 1248:2009
SIST EN ISO 1248:2009
Reference numberISO 1248:2006(E)© ISO 2006
INTERNATIONAL STANDARD ISO1248Second edition2006-09-15Iron oxide pigments — Specifications and methods of test Pigments à base d'oxydes de fer — Spécifications et méthodes d'essai
SIST EN ISO 1248:2009
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SIST EN ISO 1248:2009
ISO 1248:2006(E) © ISO 2006 – All rights reserved iiiContents Page Foreword.iv 1 Scope.1 2 Normative references.1 3 Description.2 4 Classification.2 4.1 General.2 4.2 Criteria for classification.2 5 Designation.4 6 Required characteristics and associated tolerances.5 7 Sampling.5 8 Determination of total iron, expressed as iron(III) oxide (Fe2O3).7 8.1 Method A.7 8.2 Method B.9 9 Test for presence of lead chromate.12 9.1 Reagents.12 9.2 Procedure.12 10 Determination of total calcium.12 10.1 Flame atomic absorption spectrometric (AAS) method.12 10.2 Titrimetric method.16 11 Test for organic colouring matter.18 11.1 Reagents.18 11.2 Procedure.18 11.3 Expression of results.18 12 Test report.19 Annex A (informative)
Decontamination of the waste solutions containing mercury.20 Bibliography.21
SIST EN ISO 1248:2009
ISO 1248:2006(E) iv © ISO 2006 – All rights reserved 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 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. 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. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 1248 was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee SC 2, Pigments and extenders. This second edition cancels and replaces the first edition (ISO 1248:1974), which has been technically revised. SIST EN ISO 1248:2009
INTERNATIONAL STANDARD ISO 1248:2006(E) © ISO 2006 – All rights reserved 1Iron oxide pigments — Specifications and methods of test 1 Scope This International Standard specifies the requirements and the corresponding methods of test for all manufactured and natural iron oxide pigments, in dry form, suitable for general use. These pigments are identified by Colour Index Nos.1) red 101 and 102, yellow 42 and 43, brown 6 and 7 and black 11, and includes “rapid-dispersion pigments”. This International Standard does not cover micaceous iron oxide pigments (see Note 1), transparent iron oxide pigments, granular grey iron oxide (see Note 2) or magnetic iron oxide pigments other than those of Colour Index Pigment black 11. NOTE 1 The requirements and the corresponding methods of test for micaceous iron oxide pigments are specified in ISO 10601. NOTE 2 Granular grey iron oxides are too abrasive for general use. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 385–1, Laboratory glassware — Burettes — Part 1: General requirements ISO 648, Laboratory glassware — One-mark pipettes ISO 787-1, General methods of test for pigments and extenders — Part 1: Comparison of colour of pigments ISO 787-2, General methods of test for pigments and extenders — Part 2: Determination of matter volatile at 105 °C ISO 787-3, General methods of test for pigments and extenders — Part 3: Determination of matter soluble in water — Hot extraction method ISO 787-4, General methods of test for pigments and extenders — Part 4: Determination of acidity or alkalinity of the aqueous extract ISO 787-5, General methods of test for pigments and extenders — Part 5: Determination of oil absorption value ISO 787-7, General methods of test for pigments and extenders — Part 7: Determination of residue on sieve — Water method — Manual procedure
1) The Colour Index is published by The Society of Dyers and Colourists, PO Box 244, Perkin House, 82 Grattan Road, Bradford, West Yorkshire BD1 2JB, United Kingdom; and the American Association of Textile Chemists and Colorists, National Headquarters, Box 12215, Research Triangle Park, N.C. 27709, USA. SIST EN ISO 1248:2009
ISO 1248:2006(E) 2 © ISO 2006 – All rights reserved ISO 787-9, General methods of test for pigments and extenders — Part 9: Determination of pH value of an aqueous suspension ISO 787-13, General methods of test for pigments and extenders — Part 13: Determination of water-soluble sulfates, chlorides and nitrates ISO 787-16, General methods of test for pigments and extenders — Part 16: Determination of relative tinting strength (or equivalent colouring value) and colour on reduction of coloured pigments — Visual comparison method ISO 1042, Laboratory glassware — One-mark volumetric flasks ISO 3696, Water for analytical laboratory use — Specification and test methods ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling 3 Description The iron oxide pigments covered by this International Standard consist mainly of iron oxides and hydrated iron oxides. Their colours are usually red, yellow, brown or black. 4 Classification 4.1 General In this International Standard, iron oxide pigments are classified as follows: ⎯ by groups depending on their colour; ⎯ by categories depending on their iron content, expressed as iron(III) oxide; ⎯ by types depending on their content of water-soluble matter and their total content of water-soluble chlorides and sulfates, expressed as the ions Cl– and SO42–; ⎯ by grades depending on their residue on sieve; ⎯ by classes depending on their origin. 4.2 Criteria for classification 4.2.1 Groups Depending on their colour, iron oxide pigments are divided into four groups: ⎯ reds; ⎯ yellows; ⎯ browns; ⎯ blacks. SIST EN ISO 1248:2009
ISO 1248:2006(E) © ISO 2006 – All rights reserved 34.2.2 Categories Depending on their minimum iron content, expressed as iron(III) oxide, iron oxide pigments are divided into the categories shown in Table 1. Table 1 — Categories of iron oxide pigments Minimum iron content, expressed as Fe2O3 Group Category % (by mass) Colour Index No. Red A 95 Pigment red 101 77491
B C D 70 50 10 Pigment red 102 77491 Yellow A 83 Pigment yellow 42 77492
B C D 70 50 10 Pigment yellow 43 77492 Brown A 87 Pigment brown 6 77491, 77492 or 77499
B C 70 30 Pigment brown 7 77491, 77492 and/or 77499 Black A B 95 70 Pigment black 11 77499
4.2.3 Types Depending on their content of water-soluble matter and their total content of water-soluble chlorides and sulfates, iron oxide pigments are divided into the types shown in Table 2. Table 2 — Types of iron oxide pigments Type Ia
Type II Type III Characteristic Red and brown only Red and brown only Yellow and black only All pigments Method of test Matter soluble in water (determined after drying at
105 °C), % (by mass) u 0,3 > 0,3 and u 1 u 1 > 1 and u 5 ISO 787-3 Sum of water-soluble chlorides and sulfates, expressed as the ions Cl– and SO42–, % (by mass) u 0,1
ISO 787-13 a Type I pigments are used in making anticorrosive paints.
4.2.4 Grades Depending on their residue on sieve, iron oxide pigments are divided into the grades shown in Table 3. SIST EN ISO 1248:2009
ISO 1248:2006(E) 4 © ISO 2006 – All rights reserved Table 3 — Grades of iron oxide pigments Grade 1 Grade 2 Grade 3 Characteristic Red, yellow, brown and black Method of test Residue on sieve (45 µm), % (by mass) u 0,01 > 0,01 and u 0,1 > 0,1 and u 1 ISO 787-7
4.2.5 Classes Depending on their origin, iron oxide pigments are divided into four classes: ⎯ class a
manufactured pigments without extenders; ⎯ class b
natural pigments without extenders; ⎯ class c
mixtures of natural and manufactured pigments without extenders; ⎯ class d
mixtures of pigments with extenders. For classes a, b and c, the permitted maximum content of calcium (as CaO) is shown in Table 4. 5 Designation The designation of an iron oxide pigment shall include the following. a) An indication of the colour group to which it belongs, to which may be added a more precise indication of the actual colour (preferably by means of colorimetric data). The following additional items may be included in this part of the designation: ⎯ the common name in some countries, especially for natural pigments [ochre, umber, (terra di) Sienna, etc.]; ⎯ an indication of the treatment it has undergone (e.g. burnt, washed). b) A reference to this International Standard, i.e. ISO 1248. c) The category of the iron oxide pigment. d) Its type. e) Its grade. f) Its class. EXAMPLES
Red iron oxide ISO 1248-A-I-2-a
Yellow iron oxide (washed ochre) ISO 1248-D-II-3-b. SIST EN ISO 1248:2009
ISO 1248:2006(E) © ISO 2006 – All rights reserved 56 Required characteristics and associated tolerances 6.1 For iron oxide pigments complying with this International Standard, the essential requirements are specified in Table 4 and the conditional requirements are listed in Table 5. The conditional requirements shall be specified by agreement between the interested parties. 6.2 The agreed reference pigment referred to in Table 5 shall comply with the requirements of Table 4. 7 Sampling Take a representative sample of the product to be tested, as described in ISO 15528. SIST EN ISO 1248:2009
Table 4 — Essential requirements Requirement depending on group and category Red Yellow Brown Black Characteristic A B C D A B C D A B C A B Method of test Total iron, expressed as iron(III) oxide (Fe2O3), determined on the pigment after drying at 105 °C, % (by mass) min. 95 70 50 10 83 70 50 10 87 70 30 9570 See Clause 8 Matter volatile at 105 °C, % (by mass) max. 1 1,5 2,5 2,5 1 2,5 2,5 2,5 1 2,5 2,5 1 2,5 ISO 787-2 Type I u 0,3 — u 0,3 — Type II > 0,3 and u 1 u 1 > 0,3 and u 1 u 1 Matter soluble in water (hot extraction method), % (by mass) Type III > 1 and u 5 ISO 787-3 Water-soluble chlorides and sulfates, expressed as ions Cl– and SO42– , % (by mass) Type 1 u 0,1 — u 0,1 — ISO 787-13 Grade 1 u 0,01 Grade 2 > 0,01 and u 0,1 Residue on sieve (45 µm), % (by mass) Grade 3 > 0,1 and u 1 ISO 787-7 Acidity or alkalinity of aqueous extract solution, ml of 0,1 mol/l max. 20 ISO 787-4 Presence of
lead chromate Not detectable See Clause 9 Class a 0,3 Classes b and c 5 Total calcium, expressed as calcium oxide, determined on the pigment after drying at 105 °C, % (by mass) max. Class d See Table 5 See Clause 10 Presence of organic colouring matter Not detectable See Clause 11
ISO 1248:2006(E) 6 © ISO 2006 – All rights reserved SIST EN ISO 1248:2009
ISO 1248:2006(E) © ISO 2006 – All rights reserved 7Table 5 — Conditional requirements for all groups and categories Characteristic Requirement Method of test pH value of the aqueous suspension Shall not differ by more than 1 pH scale unit from that of the agreed reference pigment (see 6.2) ISO 787-9 Oil absorption value Shall not differ by more than 15 % from that of the agreed reference pigment (see 6.2) ISO 787-5 Class a Classes b and cSee Table 4 See Clause 10 Total calcium expressed as calcium oxide, % (by mass) max. Class d To be agreed between the interested parties
Colour Equal to that of the agreed reference pigment (see 6.2) within a tolerance agreed between the interested parties ISO 787-1 Relative tinting strength
ISO 787-16
8 Determination of total iron, expressed as iron(III) oxide (Fe2O3) For the determination of the total iron content, two methods are provided. Method A (8.1) shall be used as the reference method in cases of dispute. It is recommended that mercury be removed from the waste solutions before discharge to effluent drains. A suggested procedure is given in Annex A. 8.1 Method A 8.1.1 Principle A test portion of the dried sample is dissolved in hydrochloric acid. The iron(III) is then reduced to iron(II) with tin(II) chloride solution, and the excess reducing agent is oxidized with mercury(II) chloride solution, followed by titration of the iron(II) with potassium dichromate solution, using sodium diphenylamine sulfonate as indicator. 8.1.2 Reagents During the analysis, use only reagents of recognized analytical grade and only water of at least grade 3 purity as defined in ISO 3696. WARNING — Use the reagents in accordance with the appropriate health and safety regulations. 8.1.2.1 Hydrochloric acid, concentrated, approximately 37 % (by mass),
≈ 1,19 g/ml. 8.1.2.2 Hydrochloric acid, diluted 1 + 50. Add 1 part by volume of concentrated hydrochloric acid (8.1.2.1) to 50 parts by volume of water. 8.1.2.3 Hydrofluoric acid, concentrated, approximately 40 % (by mass),
≈ 1,13 g/ml. 8.1.2.4 Sulfuric acid, diluted 1 + 1. Add carefully 1 part by volume of concentrated sulfuric acid [approximately 96 % (by mass),
≈ 1,84 g/ml] to 1 part by volume of water. SIST EN ISO 1248:2009
ISO 1248:2006(E) 8 © ISO 2006 – All rights reserved 8.1.2.5 Mixture of sulfuric and ortho-phosphoric acids Carefully mix 310 ml of concentrated sulfuric acid [approximately 96 % (by mass),
≈ 1,84 g/ml] with 250 ml of concentrated orthophosphoric acid (H3PO4) [approximately 85 % (by mass),
≈ 1,70 g/ml]. Add the resultant mixture slowly to about 400 ml of water and then dilute with water to 1 litre. 8.1.2.6 Mercury(II) chloride, saturated solution (60 g/l to 100 g/l). 8.1.2.7 Tin(II) chloride, 100 g/l solution. Dissolve 50 g of SnCl2·2H2O in 300 ml of concentrated hydrochloric acid (8.1.2.1) and dilute with water to 500 ml. Keep the solution clear by storing it in an hermetically closed flask containing a small metallic tin. 8.1.2.8 Potassium dichromate, standard volumetric solution, c(1/6 K2Cr2O7) = 0,1 mol/l. 8.1.2.8.1 Preparation Dissolve 4,903 g of K2Cr2O7, previously dried at 150 °C for 60 min, in water and dilute to the mark in a 1 000 ml one-mark volumetric flask. 8.1.2.8.2 Standardization Standardize the solution by using a standard Fe2O3 sample and the determination described in 8.1.4. 8.1.2.9 Sodium diphenylamine sulfonate indicator Dissolve 0,2 g of sodium diphenylamine sulfonate in 100 ml of water. 8.1.2.10 Potassium pyrosulfate, K2S2O7 (fine powder). 8.1.3 Apparatus Use ordinary laboratory apparatus and burettes, pipettes and one-mark volumetric flasks complying with the requirements of ISO 385-1, ISO 648 or ISO 1042, respectively. 8.1.4 Procedure 8.1.4.1 Preliminary treatment of the test portion 8.4.1.1.1 Carry out the determination in duplicate. 8.1.4.1.2 Take a suitable quantity of the sample (see Clause 7) and dry it at 105 °C for 1 h. Weigh, to the nearest 0,1 mg, a test portion of the dried sample containing approximately 0,3 g of iron (see Table 1), i.e. 0,3 g to 1,0 g of the sample depending on the expected iron content. 8.1.4.1.3 If the sample is known, or suspected, to contain carbon or organic matter (see Note in 11.3), place the test portion in a 400 ml quartz beaker and ignite at 750 °C for 1 h, and allow to cool. Alternatively, place the test portion in a porcelain crucible, ignite at 750 °C for 1 h, allow to cool, and transfer to a 400 ml beaker. 8.1.4.1.4 Place the test portion in a 400 ml beaker and add 25 ml of hydrochloric acid (8.1.2.1). Cover the beaker with a watchglass and heat at 80 °C to 90 °C to dissolve the pigment. If an insoluble residue remains, add 50 ml of water, stir, and filter off the residue using a paper filter. Wash the filter with warm hydrochloric acid (8.1.2.2), until the yellow colour of iron(III) is no longer observed. Then wash once or twice with warm water. Place the filter and the residue in a platinum crucible, dry, char the paper and finally ignite at 750 °C to 800 °C. Allow the crucible to cool. Moisten the residue in the crucible with dilute sulfuric acid (8.1.2.4), add about 5 ml of hydrofluoric acid (8.1.2.3), and heat gently to remove silica and sulfuric acid. SIST EN ISO 1248:2009
ISO 1248:2006(E) © ISO 2006 – All rights reserved 98.1.4.1.5 Add to the cool crucible 2 g of potassium pyrosulfate (8.1.2.10), then heat gently at first and then more strongly, minimizing any tendency for the flux to creep, until a clear melt is obtained. Allow the melt to cool, place the platinum crucible in a 250 ml beaker, add about 50 ml of warm water and about 5 ml of hydrochloric acid (8.1.2.1), and heat gently to dissolve the melt. Remove and rinse the platinum crucible with water, collecting the rinsing fluids in the dissolved melt. Transfer the resulting solution to the original beaker. 8.1.4.2 Determination Heat the combined filtrate until gently boiling. Avoid intense and prolonged boiling. Add, while stirring, the tin(II) chloride solution (8.1.2.7) drop by drop, until the last drop makes the solution colourless or free from yellow colour, then add one or two drops in excess. Dilute the solution to about 300 ml with cold water. Cool the solution in a water bath and then, whilst stirring vigorously, rapidly add 15 ml of mercury(II) chloride solution (8.1.2.6) to form a slight white precipitate which appears after 15 s to 20 s. One minute after adding the mercury(II) chloride, add 50 ml of sulfuric/phosphoric acid mixture (8.1.2.5) and 3 drops of sodium diphenylamine sulfonate indicator (8.1.2.9). Immediately begin to titrate slowly with potassium dichromate solution (8.1.2.8) to an endpoint when the dark green colour changes to violet. Record the volume of potassium dichromate solution used (V1). 8.1.5 Expression of results 8.1.5.1 Calculation Calculate the iron oxide content
of the pigment, w, expressed as a percentage by mass, using the equation –31179,846
0,1
10100%
tVw =
m××××× (1) 11 0,79846i.e.%V
t
w = m×× (2) where m1 is the mass, in grams, of the test portion; V1 is the volume, in millilitres, of potassium dichromate solution (8.1.2.8) used in the determination; 79,846 × 0,1 × 10–3 is the factor for the conversion of millilitres of potassium dichromate solution (8.1.2.8) to grams of Fe2O3; t is the titre of the potassium dichromate solution, as determined in 8.1.2.8.2. If the two determinations differ by more than 0,3 % (by mass), repeat the procedure. Calculate the mean of two valid determinations and report the result to the nearest 0,1 % (by mass). 8.1.5.2 Precision No precision data are currently available. 8.2 Method B 8.2.1 Principle A test portion of the dried sample is dissolved in hydrochloric acid. The iron(III) is then reduced to iron(II) with titanium(III) chloride solution under an inert atmosphere, followed by titration of the iron(II) with potassium dichromate solution, using potentiometric indication of the endpoint. SIST EN ISO 1248:2009
ISO 1248:2006(E) 10 © ISO 2006 – All rights reserved 8.2.2 Reagents During the analysis, use only reagents of recognized analytical grade and only water of at least grade 3 purity as defined in ISO 3696. WARNING — Use the reagents in accordance with the appropriate health and safety regulations. 8.2.2.1 Hydrochloric acid, concentrated, approximately 37 % (by mass),
≈ 1,19 g/ml. 8.2.2.2 Hydrochloric acid, diluted 1 + 50. Add 1 part by volume of concentrated hydrochloric acid (8.2.2.1) to 50 parts by volume of water. 8.2.2.3 Hydrofluoric acid, concentrated, approximately 40 % (by volume),
≈ 1,13 g/ml. 8.2.2.4 Sulfuric acid, diluted 1 + 1. Add carefully 1 part by volume of concentrated sulfuric acid [approximately 96 % (by volume),
≈ 1,84 g/ml] to 1 part by volume of water. 8.2.2.5 Titanium(III) chloride (TiCl3), 15 % (by mass) solution. Dissolve the solid TiCl3 in concentrated hydrochloric acid while blanketing the solution with nitrogen. Dilute to the desired concentration with distilled water which has been boiled under a nitrogen atmosphere to fully remove any oxygen; store under an inert atmosphere, e.g. nitrogen. 8.2.2.6 Potassium dichromate, standard volumetric solution, c(1/6 K2Cr2O7) = 0,25 mol/l. 8.2.2.6.1 Preparation Dissolve 12,258 g of K2Cr2O7, previously dried at 150 °C for 60 min, in water and dilute to the mark in a 1 000 ml one-mark volumetric flask. 8.2.2.6.2 Standardization Standardize the solution by using a standard Fe2O3 sample and the determination described in 8.2.4. 8.2.2.7 Potassium pyrosulfate, K2S2O7 (fine powder). 8.2.3 Apparatus Use ordinary laboratory apparatus, and pipettes and one-mark volumetric flasks complying with the requirements of ISO 648 and ISO 1042, respectively, together with the following: 8.2.3.1 Automatic titrator 8.2.3.2 Platinum electrode 8.2.3.3 Silver/silver chloride electrode 8.2.4 Procedure 8.2.4.
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