SIST EN ISO 21078-1:2008
Determination of boron(III) oxide in refractory products - Part 1: Determination of total boric oxide in oxidic materials for ceramics, glass and glazes (ISO 21078-1:2008)
Determination of boron(III) oxide in refractory products - Part 1: Determination of total boric oxide in oxidic materials for ceramics, glass and glazes (ISO 21078-1:2008)
This part of ISO 21078 specifies methods of determining boron(III) oxide in refractory products and raw materials, in mass fractions of 0,01 % or greater. It is applicable to the determination of total boron(III) oxide in oxidic materials for ceramics, glass and glazes. The determination of boron(III) oxide is carried out using one of the following four methods: a) alkaline titrimetry, which is applied to samples containing more than 0,5 % by mass of boron(III) oxide; b) azomethine H absorption spectrophotometry, which is applied to samples containing from 0,01 % by mass to 2,5 % by mass of boron(III) oxide; c) curcumin absorption spectrophotometry (rothocyanine method), which is applied to samples containing from 0,01 % by mass to 1,0 % by mass of boron(III) oxide; d) inductively coupled plasma atomic emission spectrometry (ICP-AES), which is applied to samples containing from 0,01 % by mass to 15 % by mass of boron(III) oxide.
Bestimmung des Gehaltes an Bor(III)-oxid in feuerfesten Erzeugnissen - Teil 1: Bestimmung des Gesamtgehaltes an Bor(III)-oxid in oxidischen Werkstoffen für Keramik, Glas und Glasuren (ISO 21078-1:2008)
Dieser Teil von ISO 21078 legt Verfahren zur Bestimmung von Bor(III)-oxid ab einem Massenanteil von 0,01 % in feuerfesten Erzeugnissen und Rohstoffen fest. Er gilt für die Bestimmung des Gesamtgehaltes an Bor(III)-oxid in oxidischen Werkstoffen für Keramik, Glas und Glasuren.
Die Bestimmung von Bor(III)-oxid erfolgt nach einem der folgenden vier Verfahren:
a) alkalische Titrimetrie, die bei Proben angewendet wird, deren Massenanteil an Bor(III)-oxid größer 0,5 % ist;
b) Absorptionsspektrometrie mit Azomethin H, die bei Proben angewendet wird, deren Massenanteil an Bor(III)-oxid im Bereich von 0,01 % bis 2,5 % liegt;
c) Absorptionsspektrometrie mit Curcumin (Rothocyanin-Verfahren), die bei Proben angewendet wird, deren Massenanteil an Bor(III)-oxid im Bereich von 0,01 % bis 1,0 % liegt;
d) Atomemissionsspektrometrie mit induktiv gekoppeltem Plasma (ICP AES), die bei Proben angewendet wird, deren Massenanteil an Bor(III)-oxid im Bereich von 0,01 % bis 15 % liegt.
ANMERKUNG 1 Dieses Verfahren kann durch Verwendung von modifizierten oxidischen Flussmitteln bis auf 30 % Massenanteil Bor(III)-oxid erweitert werden.
ANMERKUNG 2 Im Anhang A sind für diesen Teil von ISO 21078 Ringversuchsergebnisse aufgeführt.
Dosage de l'oxyde de bore(III) dans les produits réfractaires - Partie 1: Détermination de l'oxyde de bore(III) total dans les matériaux oxydants pour les céramiques, les verres et les émaux (ISO 21078-1:2008)
L'ISO 21078-1:2008 spécifie des méthodes de détermination de l'oxyde de bore(III) dans des produits réfractaires et des matières premières, à des concentrations supérieures ou égales à 0,01 %. Elle s'applique au dosage de l'oxyde de bore(III) total dans les matériaux oxydants pour les céramiques, les verres et les émaux.
Ugotavljanje borovega (III) oksida v ognjevzdržnih izdelkih - 1. del: Ugotavljanje celotnega borovega oksida v oksidnih materialih keramike, stekla in glazur (ISO 21078-1:2008)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 21078-1:2008
01-maj-2008
Ugotavljanje borovega (III) oksida v ognjevzdržnih izdelkih - 1. del: Ugotavljanje
celotnega borovega oksida v oksidnih materialih keramike, stekla in glazur (ISO
21078-1:2008)
Determination of boron(III) oxide in refractory products - Part 1: Determination of total
boric oxide in oxidic materials for ceramics, glass and glazes (ISO 21078-1:2008)
Bestimmung des Gehaltes an Bor(III)-oxid in feuerfesten Erzeugnissen - Teil 1:
Bestimmung des Gesamtgehaltes an Bor(III)-oxid in oxidischen Werkstoffen für Keramik,
Glas und Glasuren (ISO 21078-1:2008)
Dosage de l'oxyde de bore(III) dans les produits réfractaires - Partie 1: Détermination de
l'oxyde de bore(III) total dans les matériaux oxydants pour les céramiques, les verres et
les émaux (ISO 21078-1:2008)
Ta slovenski standard je istoveten z: EN ISO 21078-1:2008
ICS:
81.080
SIST EN ISO 21078-1:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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EUROPEAN STANDARD
EN ISO 21078-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2008
ICS 81.040.01; 81.060.01
English Version
Determination of boron (III) oxide in refractory products - Part 1:
Determination of total boron (III) oxide in oxidic materials for
ceramics, glass and glazes (ISO 21078-1:2008)
Dosage de l'oxyde de bore (III) dans les produits Bestimmung des Gehaltes an Bor(III)-oxid in feuerfesten
réfractaires - Partie 1: Détermination de l'oxyde de bore (III) Erzeugnissen - Teil 1: Bestimmung des Gesamtgehaltes an
total dans les matériaux oxydants pour les céramiques, les Bor(III)-oxid in oxidischen Werkstoffen für Keramik, Glas
verres et les émaux (ISO 21078-1:2008) und Glasuren (ISO 21078-1:2008)
This European Standard was approved by CEN on 28 December 2007.
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 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 translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official 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 STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 21078-1:2008: E
worldwide for CEN national Members.
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EN ISO 21078-1:2008 (E)
Contents Page
Foreword.3
2
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EN ISO 21078-1:2008 (E)
Foreword
This document (EN ISO 21078-1:2008) has been prepared by Technical Committee ISO/TC 33 "Refractories"
in collaboration with Technical Committee CEN/TC 187 “Refractory products and materials” the secretariat of
which is held by BSI.
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 July 2008, and conflicting national standards shall be withdrawn at the
latest by July 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 21078-1:2008 has been approved by CEN as a EN ISO 21078-1:2008 without any
modification.
3
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INTERNATIONAL ISO
STANDARD 21078-1
First edition
2008-01-15
Determination of boron(III) oxide in
refractory products —
Part 1:
Determination of total boron(III) oxide in
oxidic materials for ceramics, glass and
glazes
Dosage de l'oxyde de bore(III) dans les produits réfractaires —
Partie 1: Détermination de l'oxyde de bore(III) total dans les matériaux
oxydants pour les céramiques, les verres et les émaux
Reference number
ISO 21078-1:2008(E)
©
ISO 2008
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ISO 21078-1:2008(E)
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ii © ISO 2008 – All rights reserved
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ISO 21078-1:2008(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 2
4 Preparation of the test sample . 2
5 Number of determinations . 2
6 Determination of boron(III) oxide by alkaline titrimetry. 3
7 Determination of boron(III) oxide by azomethine H absorption spectrophotometry. 5
8 Determination of boron(III) oxide by curcumin absorption spectrophotometry. 8
9 Determination of boron(III) oxide by inductively coupled plasma atomic emission
spectrometry (ICP-AES) . 12
10 Expression of test results. 14
11 Test report. 15
Annex A (informative) Interlaboratory test results . 16
© ISO 2008 – All rights reserved iii
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ISO 21078-1:2008(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 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 21078-1 was prepared by Technical Committee ISO/TC 33, Refractories, in collaboration with Technical
Committee CEN/TC 187, Refractory products and materials.
ISO 21078 consists of the following parts, under the general title Determination of boron(III) oxide in refractory
products:
⎯ Part 1: Determination of total boron(III) oxide in oxidic materials for ceramics, glass and glazes
⎯ Part 2: Acid extraction method for the determination of boron(III) oxide in binder components
iv © ISO 2008 – All rights reserved
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INTERNATIONAL STANDARD ISO 21078-1:2008(E)
Determination of boron(III) oxide in refractory products —
Part 1:
Determination of total boron(III) oxide in oxidic materials for
ceramics, glass and glazes
1 Scope
This part of ISO 21078 specifies methods of determining boron(III) oxide in refractory products and raw
materials, in mass fractions of 0,01 % or greater. It is applicable to the determination of total boron(III) oxide in
oxidic materials for ceramics, glass and glazes.
The determination of boron(III) oxide is carried out using one of the following four methods:
a) alkaline titrimetry, which is applied to samples containing more than 0,5 % by mass of boron(III) oxide;
b) azomethine H absorption spectrophotometry, which is applied to samples containing from 0,01 % by
mass to 2,5 % by mass of boron(III) oxide;
c) curcumin absorption spectrophotometry (rothocyanine method), which is applied to samples containing
from 0,01 % by mass to 1,0 % by mass of boron(III) oxide;
d) inductively coupled plasma atomic emission spectrometry (ICP-AES), which is applied to samples
containing from 0,01 % by mass to 15 % by mass of boron(III) oxide.
NOTE 1 The method can be extended to 30 % boron(III) oxide using modified oxidic fluxes.
NOTE 2 Interlaboratory test results for this part of ISO 21078 are given in Annex A.
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 31-0, Quantities and units — Part 0: General principles
ISO 836, Refractories — Vocabulary
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 6353-2, Reagents for chemical analysis — Part 2: Specifications — First series
ISO 6353-3, Reagents for chemical analysis — Part 3: Specifications — Second series
© ISO 2008 – All rights reserved 1
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ISO 21078-1:2008(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 836 and the following apply.
3.1
dry unshaped refractories
dry particles and/or powder of unshaped refractories
3.2
wet unshaped refractories
wet particles and/or powder of unshaped refractories with liquid such as mortar and a mixture of
refractory-aggregate and pitch or resin
4 Preparation of the test sample
4.1 Refractory brick or its raw material
Carry out sampling in accordance with the contract between the user and producer. Take a specified quantity
from a lot of the sample and crush to pass through a 6,7 mm sieve (see ISO 3310-1). Reduce to about 100 g
by riffling or coning and quartering, then grind all the reduced sample to pass through a 300 µm sieve
(ISO 3310-1).
4.2 Unshaped refractories
Prepare two portions of approximately 100 g each of the sample for analysis (both dry and wet) and crush to
pass through a 300 µm sieve (see ISO 3310-1) in accordance with the following procedure.
4.3 Dry unshaped refractories
Take one bag or 5 kg of the sample from a lot, reduce to about 100 g as described in 4.1 and crush to pass
through a 300 µm sieve.
4.4 Wet unshaped refractories
Take a specified quantity from the sample and spread on a heat-resistant plate that does not react with the
sample (for example, a polyethylene tetrafluoride plate) to form a charge of 10 mm thickness. Dry the sample
in an air-bath or oven at 110°C ± 5°C for a minimum of 10 h. Then crush to pass through a 6,7 mm sieve,
reduce to about 100 g by riffling or coning and quartering, and grind to pass through a 300 µm sieve (see
ISO 3310-1).
4.5 Laboratory sample
Reduce the laboratory sample from 4.1 or 4.2 to approximately 25 g by coning and quartering, and grind to
pass through a 106 µm sieve. This is the test sample for analysis. Transfer it into a container (e.g. a flat
weighing bottle (50 mm × 30 mm) or sample tube (50 mm × 25 mm), dry in an oven at 110°C ± 5°C for a
minimum of 2 h, cool and store it in a desiccator.
4.6 Weighing of test portion
Weigh the quantity of the test portion for the chemical analysis specified for the particular procedure, to the
nearest 0,1 mg, using an analytical balance and record the actual mass.
5 Number of determinations
Carry out simultaneous duplicate determinations. Carry out a blank test on the reagents and make appropriate
deductions from the results.
2 © ISO 2008 – All rights reserved
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ISO 21078-1:2008(E)
6 Determination of boron(III) oxide by alkaline titrimetry
6.1 Principle
The sample is fused with sodium hydroxide in a dish placed in a furnace at about 600 °C. After cooling, the
melt is dissolved in water and the sample solution made up to about 100 ml with water. The interfering ions
left in the sample solution are precipitated by adding calcium carbonate. After first adjusting the pH value to
6,5 with sodium hydroxide solution, mannitol is added and the H+ ions liberated as the result are titrated with
sodium hydroxide to obtain a pH value of 6,8.
6.2 Reagents
Use only reagents of known analytical purity and water conforming to the requirements of grade 2 of ISO 3696
(e.g. double-distilled water).
The boron and borate ion concentrations in the water and the reagents shall be negligible compared with the
lowest concentration to be determined. All solutions are aqueous, unless otherwise specified.
6.2.1 Sodium hydroxide (ISO 6353-2 R 34), assay, minimum mass fraction 98 %.
6.2.2 Hydrochloric acid (concentrated), (ISO 6353-2 R 13), mass fraction 35 %.
6.2.3 Hydrochloric acid (1+1), add 1 volume of hydrochloric acid (concentrated) to 1 volume of water.
6.2.4 Calcium carbonate (ISO 6353-3 R 53), assay, minimum mass fraction 99,5 %.
6.2.5 Bromocresol purple solution, C H Br O S, 1 g/l.
21 16 2 5
Dissolve 0,1 g of bromocresol purple in water and dilute to approximately 100 ml. Keep this solution in the
dark at low temperature.
6.2.6 Boron(III) oxide standard solution, 0,1 mg B O /ml.
2 3
Transfer approximately 0,5 g of boric acid into a 100 ml beaker, spread it as a thin layer and dry for 24 h in a
desiccator. Weigh 0,177 6 g of this dry boric acid and transfer into a 200 ml plastic beaker. Dissolve in
approximately 100 ml of water and dilute precisely to 1 000 ml in a volumetric flask.
6.2.7 D(−)-mannitol, C H O .
6 14 6
6.2.8 Sodium hydroxide standard volumetric solution.
Transfer 50 g of sodium hydroxide into a polyethylene bottle, add 50 ml of water, and dissolve with cooling.
Allow to stand for several days with a cover, pipette 4,0 ml of the supernatant fraction, and dilute to 2 000 ml
in a volumetric flask. Transfer this solution into a polyethylene bottle using a 25 ml automatic filling burette
with soda-lime tubes to absorb the carbon dioxide in the air.
Pipette precisely 100 ml of boron(III) oxide standard solution (0,1 mg/ml) into a 200 ml beaker and stir by
using a magnetic stirrer, put a pH electrode into the solution and add drops of the sodium hydroxide standard
volumetric solution until the pH is 6,5. Remove the electrode, add 10 g of D(−)-mannitol, set the electrode
again, and titrate with the sodium hydroxide standard volumetric solution until the pH is 6,8.
Calculate the equivalent factor, F, the mass in g, of boron(III) oxide equivalent to 1 ml of sodium hydroxide
standard volumetric solution, using Equation (1).
0,01
F= (1)
V
where V is the volume, in ml, of titration of sodium hydroxide standard volumetric solution after addition of
D(−)-mannitol.
© ISO 2008 – All rights reserved 3
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ISO 21078-1:2008(E)
6.3 Apparatus
Ordinary laboratory apparatus and the following.
6.3.1 Vitreous carbon dishes, of suitable nominal capacity.
6.3.2 Vitreous carbon lids, to fit 6.3.1.
6.3.3 Muffle furnace, capable of being controlled at temperatures up to at least 700 °C.
6.3.4 pH meter, with a glass electrode.
NOTE Automated titration equipment with a piston-operated burette and magnetic stirrer may be used to facilitate the
analysis.
6.4 Mass of test portion
Weigh out 1,00 g of the test sample.
NOTE The mass of the test portion is a function of the boron mass fraction. It is usually 1,0 g.
6.5 Procedure
Weigh 1 g to 2 g of sodium hydroxide into a dish, cover the dish and fuse it in the furnace at approximately
600 °C for about 10 min. After cooling in the desiccator, add the weighed sample, cover it with 1 g to 2 g of
sodium hydroxide, cover the dish and dissolve by digestion at approximately 600 °C for about 30 min until a
clear melt is obtained, swirling repeatedly. After cooling, transfer the melt cake to a 250 ml beaker, dissolve
any residue in the dish with water and transfer it to the beaker, repeating this procedure several times if
necessary. Make up the solution to about 100 ml with water and heat until the melt cake has disintegrated.
Standardize the sample solution by titrating against hydrochloric acid (1+1), using bromocresol purple as
indicator to precipitate interfering ions, ensuring that the indicator changes from violet to yellow. Then add an
excess of a further 2 ml of hydrochloric acid (1+1), heat to boiling and allow to boil for 1 to 2 min. Remove the
beaker from the hotplate and, after about 2 min, add a total of 1,5 g of calcium carbonate a little at a time, then
boil again for a short time. Filter off the precipitate using a white-ribbon filter and wash it eight times with hot
water. Transfer the residue to a 250 ml beaker, acidify with hydrochloric acid (1+1) and repeat the CaCO
3
precipitation as described above.
Make up the combined filtrate to about 250 ml with water and boil it for a short time. After cooling, adjust the
pH value of the test solution to 6,5 with sodium hydroxide standard volumetric solution using the glass
electrode of the pH meter. Now add 20 g of D(−)-mannitol to the solution and dissolve it while stirring. Then
titrate with sodium hydroxide standard volumetric solution to a pH value of 6,8 and read off the volume of
solution used to titrate from a pH value of 6,5 to a pH value of 6,8.
6.6 Blank test
Carry out the procedure given in 6.5 without the sample.
6.7 Calculation
Calculate the mass fraction of boron(III) oxide in the sample, w , as a percentage, using Equation (2):
B1
()VV−×F
12
w=×100 (2)
B1
m
4 © ISO 2008 – All rights reserved
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ISO 21078-1:2008(E)
where
V is the volume, in ml, of sodium hydroxide standard volumetric solution used for titration of the test
1
solution after addition of D(−)-mannitol;
V is the volume, in ml, of sodium hydroxide standard volumetric solution used for titration of the blank
2
solution after addition of D(−)-mannitol;
F is the equivalent factor, in g, of boron(III) oxide equivalent to 1 ml of sodium hydroxide standard
volumetric solution;
m is the mass, in g, of the test portion in 6.4.
6.8 Interferences
If the D(−)-mannitol used for the determination is acidic, subtract the equivalent volume of sodium hydroxide
solution from the volume used in the titration.
Germanium oxide will interfere with this alkaline titrimetry method. Germanium oxide is highly unlikely to be
present in the materials in the scope of this part of ISO 21078. However, if this part of ISO 21078 is applied to
glass samples and the presence of germanium oxide is suspected, one of the other three alternative
procedures shall be used.
7 Determination of boron(III) oxide by azomethine H absorption spectrophotometry
7.1 Principle
The sample is fused with sodium hydroxide in a dish placed in a furnace at about 600 °C. After cooling, the
melt is dissolved in water and the sample solution made up to about 100 ml with water. The pH value of the
sample solution is adjusted to 5,2, azomethine H is added and the yellow complex is determined
photometrically at a wavelength of 415 nm against reference solutions.
7.2 Reagents
Use only reagents of known analytical purity and water conforming to the requirements of grade 2 of ISO 3696
(e.g. double-distilled water).
The boron and borate ion concentrations in the water and the reagents shall be negligible compared with the
lowest concentration to be determined. All solutions are aqueous unless otherwise specified.
7.2.1 Sodium hydroxide (ISO 6353-2 R 34), assay, minimum mass fraction 98 %.
7.2.2 Hydrochloric acid (concentrated) (ISO 6353-2 R 13), mass fraction 35 %.
7.2.3 Hydrochloric acid (1+1).
Add 1 volume of hydrochloric acid (concentrated) to 1 volume of water.
7.2.4 Boric acid, H BO .
3 3
7.2.5 Boron(III) oxide stock solution, 1 mg B O /ml.
2 3
Transfer approximately 2 g of boric acid into a 100 ml beaker, spread it as a thin layer and dry for 24 h in a
desiccator. Weigh 1,776 g of this dry boric acid and transfer into a 200 ml plastic beaker. Dissolve in
approximately 100 ml of water and dilute precisely to 1 000 ml in a volumetric flask.
7.2.6 Boron(III) oxide standard solution No. 1, 0,1 mg B O /ml.
2 3
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ISO 21078-1:2008(E)
Pipette 10 ml of the boron(III) oxide stock solution into a 100 ml volumetric flask and make up to the mark with
water. Keep the solution, which is stable only for about 9 h, in a plastic bottle.
7.2.7 Boron(III) oxide standard solution No 2, 0,01 mg B O /ml.
2 3
Pipette 10 ml of boron(III) oxide standard solution No. 1 into a 100 ml plastic volumetric flask and make up to
the mark with water. Make up a fresh solution before every determination.
7.2.8 Sodium salt of azomethine H, C H NNaO S .
7 12 8 2
7.2.9 L(+)-ascorbic acid, C H O .
6 8 6
7.2.10 Azomethine H solution.
Mix 1 g of azomethine H and 3 g of ascorbic acid in a 100 ml glass beaker with about 6 ml of water, transfer
the mixture to a 100 ml volumetric flask and make up to the mark with water. During mixing, the solution
becomes clear. Transfer the solution to a plastic bottle and store it in a refrigerator; it will be stable for one
week.
7.2.11 Ammonium acetate, CH COONH .
3 4
7.2.12 Acetic acid (ISO 6353-2 R 1), minimum mass fraction 99,7 % as CH COOH.
3
7.2.13 Buffer solution.
Dissolve 200 g of ammonium acetate in a glass beaker with about 200 ml of water, add 50 ml of acetic acid,
use water to rinse the solution into a 500 ml volumetric flask and make up to the mark with water. Store the
solution in a plastic bottle.
7.2.14 Ammonium hydroxide solution (concentrated) (ISO 6353-2 R 3), minimum mass fraction 25 % as
NH .
3
7.2.15 Ammonium hydroxide solution (1+6), NH OH.
4
7.2.16 Disodium ethylenediaminetetraacetate (EDTA-Na ), C H N Na O⋅2H O.
2 10 14 2 2 8 2
7.2.17 Citric acid monohydrate, C H O⋅H O.
6 8 7 2
7.2.18 Complexing solution.
Mix 37,2 g of disodium ethylenediaminetetraacetate and 5 g of citric acid monohydrate in a beaker with about
300 ml of water and add 2 mol/I ammonium hydroxide solution until the reagents have dissolved and the
solution is clear. Then, using the glass electrode of the pH meter, adjust the pH value to 5 by adding further
2 mol/l ammonium hydroxide solution. Make up to 500 ml with water.
7.2.19 2,2′,2″,4,4′-pentamethoxytriphenylcarbinol, C H O .
24 26 6
7.2.20 Ethanol (ISO 6353-2 R 11), minimum mass fraction 99,8 %, as C H OH.
2 5
7.2.21 Indicator solution, prepared by dissolving 50 mg of 2,2′,2″,4,4′-pentamethoxytriphenylcarbinol in
50 ml of ethanol while heating gently. The indicator changes from violet to colourless at a pH value of 2 to 3.
7.2.22 Sodium chloride solution, 241,7 g/l.
7.3 Apparatus
Ordinary laboratory apparatus and the following.
7.3.1 Vitreous carbon dishes, of suitable nominal capacity.
6 © ISO 2008 – All rights reserved
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ISO 21078-1:2008(E)
7.3.2 Vitreous carbon lids, to fit 7.3.1.
7.3.3 Muffle furnace, capable of being controlled at temperatures up to at least 700 °C.
7.3.4 Photometer, with 1 cm cell.
7.4 Mass of test portion
Weigh out 0,50 g of the test sample.
NOTE The mass of the test portion is a function of the mass fraction of boron . It will usually be 0,5 g.
7.5 Procedure
Weigh 1 g to 2 g of sodium hydroxide into a dish, cover the dish and fuse in the furnace at approximately
600 °C for about 10 min. After cooling in the desiccator, add the weighed sample, cover it with 1 g to 2 g of
sodium hydroxide, cover the dish and dissolve by digestion at approximately 600 °C for about 30 min until a
clear melt is obtained, swirling repeatedly. Introduce 25 ml of hydrochloric acid (1+1) into a 100 ml plastic
volumetric flask. After cooling the melt, dissolve the melt cake in a little hot water and transfer it to the
volumetric flask, repeating this process several times if necessary. After cooling, make up to the mark with
water.
This solution is designated as stock solution S1.
Prior to the analysis, remove any silicon(IV) oxide precipitate present in the sample solutions by centrifuging,
filtering or allowing to settle.
Pipette an aliquot portion of the stock solution S1 into a 50 ml plastic volumetric flask. The volume of the
aliquot portion to be taken depends on the expected mass fraction of boron(III) oxide and is shown in Table 1.
Table 1 — Preparation of test solution
Mass fraction of Aliquot portion of Volume of sodium
boron(III) oxide stock solution S1 chloride solution (7.2.22)
% ml ml
2,5 to 0,5 2 5,5
0,6 to 0,11 5 4,8
0,12 to 0,01 25 0
An aliquot portion of stock solution S1 may also be chosen: less than 25 ml. In this case, calculate the volume
of sodium chloride solution to be added, V , in ml, using Equation (3):
S
1000
VV=−1,45 0,058× × (3)
()
SA
241,7
where V is the volume of the aliquot portion, in ml.
A
Add the volume of sodium chloride solution specified in Table 1, two drops of indicator solution and 5 ml of
complexing solution. Neutralize with ammonium hydroxide solution (1+6) until the indicator colour just
disappears. Then add 5 ml of buffer solution and 5 ml of azomethine H solution, make the volumetric flask up
to the mark with water and allow to stand in the dark for 4 h. The boron concentration in the test solution will
then be about 0,2 mg/l to 1 mg/l. Measure the boron concentration photometrically using a 1 cm cell, at a
wavelength of 415 nm against the calibration solution, with water in the reference cell.
© ISO 2008 – All rights reserved 7
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ISO 21078-1:2008(E)
7.6 Blank test
Carry out the procedure described in 7.5 but omit the fusion process without using the sample.
The solution obtained corresponds to stock solution S1 and is designated as blank
...
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