EN 973:2002

SLOVENSKI STANDARD
01-december-2002
Kemikalije, ki se uporabljajo za pripravo pitne vode – Natrijev klorid za
regeneracijo ionskih izmenjevalnikov
Chemicals used for treatment of water intended for human consumption - Sodium
chloride for regeneration of ion exchangers
Produkte zur Aufbereitung von Wasser für den menschlichen Gebrauch - Natriumchlorid
zum Regenerieren von Ionenaustauschern
Produits chimiques utilisés pour le traitement de l'eau destinée a la consommation
humaine - Chlorure de sodium pour la régénération des résines échangeuses d'ions
Ta slovenski standard je istoveten z: EN 973:2002
ICS:
13.060.20 Pitna voda Drinking water
71.100.80 .HPLNDOLMH]DþLãþHQMHYRGH Chemicals for purification of
water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 973
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2002
ICS 71.100.80
English version
Chemicals used for treatment of water intended for human
consumption - Sodium chloride for regeneration of ion
exchangers
Produits chimiques utilisés pour le traitement de l'eau Produkte zur Aufbereitung von Wasser für den
destinée à la consommation humaine - Chlorure de sodium menschlichen Gebrauch - Natriumchlorid zum
pour la régénération des résines échangeuses d'ions Regenerieren von Ionenaustauschern
This European Standard was approved by CEN on 23 December 2001.
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,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, 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
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 973:2002 E
worldwide for CEN national Members.

Contents
page
Foreword.3
1 Scope .4
2 Normative references .4
3 Description .5
3.1 Identification.5
3.2 Commercial forms .5
3.3 Physical properties.5
3.4 Chemical properties .7
4 Purity criteria.7
4.1 Composition of commercial product .7
4.2 Impurities and main by-products .8
4.3 Chemical parameters.8
5 Test methods.9
5.1 Sampling.9
5.2 Analyses .9
6 Labelling – Transportation - Storage .10
6.1 Means of delivery.10
6.2 Risk and safety labelling in accordance with the EU directives.10
6.3 Transportation regulations and labelling .10
6.4 Marking .10
6.5 Storage.10
Annex A (informative)  General information on sodium chloride.11
A.1 Origin.11
A.2 Use.11
A.3 Rules for safe handling and use.11
A.4 Emergency procedures .12
Annex B (normative)  Analytical methods .13
B.1 Determination of antimony, arsenic, cadmium, chromium, lead, nickel and selenium
(inductively coupled plasma optical emission spectrometry (ICP/OES)) .13
B.2 Determination of total mercury (cold vapour atomic absorption spectrometry) .19
B.3 Determination of water-soluble hexacyanoferrate (II) (molecular absorption spectrometry) .25
B.4 Determination of potassium (Flame atomic absorption spectrometric method) .28
Annex C (informative)  Determination of cadmium, chromium, nickel and lead (flame atomic
absorption spectrometry.32
C.1 Determination of cadmium.32
C.2 Determination of chromium.36
C.3 Determination of nickel .40
C.4 Determination of lead .43
Annex D (informative)  Determination of arsenic, antimony and selenium (atomic absorption
spectrometry hydride technique).48
D.1 General principle.48
D.2 Interferences.48
D.3 Reagents.48
D.4 Apparatus .50
D.5 Procedure .51
D.6 Calculation.53
Foreword
This document (EN 973:2002) has been prepared by Technical Committee CEN/TC 164 "Water supply", the
secretariat of which is held by AFNOR.
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 February 2003, and conflicting national standards shall be withdrawn at the latest
by February 2003.
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, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain,
Sweden, Switzerland and the United Kingdom.
The annexes A, C and D are informative.
Annex B is normative.
Introduction
In respect of potential adverse effects on the quality of water intended for human consumption, caused by the
product covered by this standard :
a) this standard provides no information as to whether the product may be used without restriction in any of the
Member States of the EU or EFTA ;
b) it should be noted that, while awaiting the adoption of verifiable European criteria, existing national regulations
concerning the use and/or the characteristics of this product remain in force.
1 Scope
This European Standard is applicable to sodium chloride intended for use only in water treatment apparatus, for the
regeneration of ion exchangers, intended for water for human consumption. It describes the characteristics and
specifies the requirements and the corresponding test methods for sodium chloride. It gives information on its use
in water treatment.
2 Normative references
This European Standard incorporates by dated and 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).
EN ISO 3696, Water for analytical laboratory use - Specification and test methods (ISO 3696:1987).
ISO 2479, Sodium chloride for industrial use – Determination of matter insoluble in water or in acid and preparation
of principal solutions for other determinations.
ISO 2480, Sodium chloride for industrial use – Determination of sulfate content – Barium sulfate gravimetric
method.
ISO 2482, Sodium chloride for industrial use – Determination of calcium and magnesium contents – EDTA
complexometric method.
ISO 2483, Sodium chloride for industrial use – Determination of the loss of mass at 110 °C.
ISO 3165, Sampling of chemical products for industrial use - Safety in sampling.
ISO 6206, Chemical products for industrial use – Sampling – Vocabulary.
ISO 6227, Chemical products for industrial use – General method for determination of chloride ions –
Potentiometric method.
ISO 8213, Chemical products for industrial use – Sampling techniques – Solid chemical products in the form of
particles varying from powders to coarse lumps.
3 Description
3.1 Identification
3.1.1 Chemical name
Sodium chloride.
3.1.2 Synonym or common name
Salt.
3.1.3 Relative molecular mass
58,45.
3.1.4 Empirical formula
NaCl.
3.1.5 Chemical formula
NaCl.
1)
3.1.6 CAS Registry Number
7647-14-5.
2)
3.1.7 EINECS Reference
231-598-3.
3.2 Commercial forms
The product is available as rock salt, sea salt or evaporated salt, and it is supplied as free-flowing crystals or their
compacted forms.
3.3 Physical properties
3.3.1 Appearance
The product is white and crystalline.
3.3.2 Density
The density of the solid crystal is 2,16 g/cm at 20 °C.
The bulk density depends on the particle size distribution.
3.3.3 Solubility (in water)
The solubility of the product depends on the temperature as given in Figure 1.

1) Chemical Abstract Service Registry Number.
2) European Inventory of Existing Commercial Chemical Substances.
Temperature NaCl solution
°C % (m/m)
- 10 25,0
0 26,34
10 26,35
20 26,43
30 26,56
40 26,71
50 26,89
60 27,09
70 27,30
80 27,53
90 27,80
100 28,12
Key
1 Transition point
NaCl
NaCl.2H O
Figure 1 - Solubility curve for sodium chloride in water
3.3.4 Vapour pressure
Not applicable.
3)
3.3.5 Boiling point at 100 kPa
Not applicable.
3.3.6 Melting point
802 °C.
3.3.7 Specific heat
Approximately 850 J/(kg⋅K) at 25 °C for the solid.
3.3.8 Viscosity (dynamic)
The viscosity of the saturated solution at 20 °C is approximately 1,9 mPa⋅s.
3.3.9 Critical temperature
Not applicable.
3) 100 kPa = 1 bar.
3.3.10 Critical pressure
Not applicable.
3.3.11 Physical hardness
The hardness of solid salt is given as 2 to 2,5 on the Mohrs' scale of hardness.
3.4 Chemical properties
Sodium chloride is stable, non-volatile and aqueous solutions have good electrical conductivity.
Sodium chloride is decomposed by a number of acids. It reacts with sulfuric acid, phosphoric acid and strong
oxidizing agents. The reactions are often complex and require heat for completion.
NOTE Under certain conditions a sodium chloride solution can cause corrosion of metallic surfaces.
4 Purity criteria
Limits have been given for impurities and chemical parameters where these are likely to be present in significant
quantities from the current production process and raw materials. If a change in the production process or raw
materials leads to significant quantities of other impurities or by-products being present, this shall be notified to the
user.
4.1 Composition of commercial product
The content of sodium chloride in the dry product shall not be less than :
 grade A : 99,4 % (m/m) of dry NaCl ;
 grade B : 98,5 % (m/m) of dry NaCl.
4)
NOTE An anticaking agent, sodium or potassium hexacyanoferrate , is allowed up to a maximum level in the final product
-4
of 20 mg/kg, expressed as the anhydrous hexacyanoferrate ion [Fe(CN )] and for the determination see B.3.
4) E number 535 or 536 (see [2]).
4.2 Impurities and main by-products
The product shall conform to the requirements specified in Table 1 and Table 2.
Table 1 – Impurities
Limit
% (m/m) of NaCI content
Impurity
Water-insoluble matter Grade A Grade B
max. 0,05 0,35
Table 2 – Moisture content
Limit
% (m/m) of NaCI content
Impurity
Moisture content Dry salt Humid salt
max 0,6 5
Potassium, calcium, magnesium and sulfate are natural impurities. Their contents are not relevant.
4.3 Chemical parameters
The product shall conform to the requirements specified in Table 3.
Table 3 – Chemical parameters
Parameter Limits in mg/kg of
commercial product
Arsenic (As) max. 13
Cadmium (Cd) max. 1,3
Chromium (Cr) max. 13
Mercury (Hg) max. 0,26
Nickel (Ni) max. 13
Lead (Pb) max. 13
Antimony (Sb) max. 2,6
Selenium (Se) max. 2,6
NOTE Other chemical parameters and indicator parameters as listed in
EU Directive 98/83/EC (see [1] are not relevant in sodium chloride.
5 Test methods
5.1 Sampling
A test sample of about 500 g shall be taken for analysis, ensuring that it is representative of the whole batch, and
taking account of ISO 3165 and also ISO 6206. Prepare the laboratory sample(s) required in accordance with
ISO 8213.
NOTE It should be ensured that no trace of the impurities to be determined is introduced in the sample during the sampling
operations.
5.2 Analyses
5.2.1 Main product
The percentage by mass (% (m/m)) of sodium chloride (NaCI) shall be determined by calculation, on the basis of
the results of the determinations of sulfate (according to ISO 2480), halogens (according to ISO 6227), calcium and
magnesium (according to ISO 2482), potassium (see B.4) and loss of mass on drying (according to ISO 2483).
Convert sulfate to calcium sulfate and unused calcium to calcium chloride, unless sulfate in sample exceeds the
amount necessary to combine with calcium, in which case convert calcium to calcium sulfate and unused sulfate to
first to magnesium sulfate and the remaining sulfate to sodium sulfate. Convert unused magnesium to magnesium
chloride. Convert potassium to potassium chloride. Convert unused halogens to sodium chloride. Report the
sodium chloride contents on a dry matter basis, multiplying the percentage of sodium chloride by 100/(100 - P),
where P in the percentage mass by mass of the loss of mass on drying (see 5.2.2.2).
5.2.2 Impurities
5.2.2.1 Water-insoluble matter
The content of water- insoluble matter shall be determined in accordance with ISO 2479.
5.2.2.2 Moisture content
The loss of mass at 110 °C shall be determined in accordance with ISO 2483.
5.2.3 Chemical parameters
5.2.3.1 Arsenic, cadmium, chromium, nickel, lead, antimony, selenium
The contents of chemical parameters, except for mercury, shall be determined by inductively coupled plasma
optical emission spectrometry (ICP/OES) (see B.1).
NOTE Alternatively the determination of contents of some chemical parameters can be carried out by atomic absorption
spectrometry (AAS) and the analytical methods are given in annex C and annex D.
5.2.3.2 Mercury
The content of mercury shall be determined by cold vapour atomic absorption spectrometry (see B.2).
6 Labelling – Transportation - Storage
6.1 Means of delivery
Sodium chloride shall be delivered in bulk or in bags.
In order that the purity of the product is not affected, the means of delivery shall not have been used previously for
any different product or it shall have been specially cleaned and prepared before use.
6.2 Risk and safety labelling in accordance with the EU directives
Sodium chloride is not subjected to labelling regulations.
6.3 Transportation regulations and labelling
5)
Sodium chloride is not listed under a UN Number . Sodium chloride is not classified as a dangerous product for
road, rail, sea and air transportation.
6.4 Marking
Each container shall be marked with at least the following information :
 the name "Sodium chloride, regeneration salt" or "sodium chloride, salt for water softening”, "compacted dry
salt" or "humid salt", trade name and grade ;
 the net mass ;
 the name and the address of supplier and/or manufacturer ;
 the statement "this product conforms to EN 973, grade.".
6.5 Storage
6.5.1 Long term stability
Sodium chloride is stable during long term storage, providing it is kept in a dry place.
6.5.2 Storage incompatibilities
Sodium chloride shall be stored in hygienic and safe conditions so as to avoid any risk of contamination.
The product shall not be allowed to come into contact with sulfuric acid, phosphoric acid and strong oxidizing
agents.
5) United Nations Number.
Annex A
(informative)
General information on sodium chloride
A.1 Origin
a) Rock salt : Salt produced by mining salt deposits of different geological formations derived from ancient seas.
b) Sea salt : Salt produced by sea water evaporation via the action of sun and wind.
c) Evaporated salt : Salt produced by evaporating water from a salt solution in a special evaporator leading to
the recrystallization of the salt.
A.2 Use
A.2.1 Function
Regeneration of the resin in ion exchange apparatus is performed with a solution of sodium chloride.
A.2.2 Form in which the product is used
It is used in the form of a saturated solution that is diluted before being applied to the resin.
A.2.3 Consumption of salt for regeneration of resins
The consumption is variable and depends on the mineral content of water, the type of resin and the performance of
the apparatus.
A.2.4 Means of application
An appropriate dosage device such as a metering pump controls the sodium chloride consumption.
A.2.5 Secondary effects in ion exchange apparatus
None.
A.2.6 Removal of excess product
Not applicable.
A.3 Rules for safe handling and use
No particular precaution is necessary.
A.4 Emergency procedures
A.4.1 First aid
Not applicable.
A.4.2 Spillage
The product should be collected, then the area should be rinsed with plenty of water
A.4.3 Fire
Sodium chloride is not combustible.
Annex B
(normative)
Analytical methods
B.1 Determination of antimony, arsenic, cadmium, chromium, lead, nickel and selenium
(inductively coupled plasma optical emission spectrometry (ICP/OES))
B.1.1 General
The range covered for each element is given in the Table B.1
Table B.1 - Concentration range
Element Concentration range, in mg/kg of
commercial product
As 3 to 50
Cd 0,2 to 50
Cr 0,3 to 50
Ni 0,6 to 50
Pb 6 to 50
Sb 3 to 50
Se 2 to 50
NOTE Different types of ICP/OES instruments can have different performance levels. The performance depends also on
the quality of the reagents. This means that the mentioned values should be considered as indicative values.
The limits quoted in Table B.1 are based on the equation LOQ· ()limit of quantification = 10 swhere s is the
r r
repeatability standard deviation of test samples having concentrations near the expected LOQ.
B.1.2 Principle
Dissolution of the sample with nitric acid (0,1 mol/l) and direct nebulization of the acid solution into an inductively
coupled argon plasma formed by a high frequency. Measurement of the radiation at specific wavelengths using
background correction.
NOTE The use of reference element (internal standard) as scandium, yttrium, cobalt etc can improve the quality of the
results especially using a simultaneous spectrometer. Every mention of this optional reagent (here scandium) is stated in
brackets.
B.1.3 Reagents
All reagents shall be of recognized analytical grade and the water used shall conform to grade 3 in accordance with
EN ISO 3696.
Store all prepared solutions in polyethylene or polytetrafluorethylene (PTFE) flasks to prevent contamination.
B.1.3.1 Nitric acid solution r » 1,40 g/ml, 65 % (m/m).
B.1.3.2 Hydrochloric acid solution r » 1,19 g/ml, 37 % (m/m).
B.1.3.3 Sodium chloride solution, c(NaCl) = 250 g/l.
Dissolve 250 g of very pure NaCl (high purity grade) with water and transfer to a 1 000 ml volumetric flask. Make up
to the mark with water and mix.
NOTE The contents of the particular elements in the high purity sodium chloride reagent should be less than one tenth of
the lower limits quoted in Table B.1.
B.1.3.4 Scandium (reference element) solution, c(Sc) = 50 mg/l
Transfer 50 ml of a scandium stock solution c(Sc) = 1 000 mg/l and 10 ml nitric acid (B.1.3.1) to a 1 000 ml
volumetric flask. Make up to the mark with water and mix.
B.1.3.5 As, Cd, Cr, Ni, Pb, Sb or Se element, stock solution, c(element) = 1 000 mg/l commercial solution.
B.1.3.6 Argon the pressure shall not less than 700 kPa and the argon used can be compress or liquefied gas.
B.1.4 Apparatus
Ordinary laboratory apparatus and glassware together with the following :
NOTE All vessels (glassware, polyethylene, polypropylene and polytetrafluorethylene (PTFE) flasks) should be washed
with hydrochloric acid c(HCl) » 6 mol/l and water successively.
B.1.4.1 Inductively coupled plasma optical emission spectrometer ICP/OES fitted with nebulizer for high
salt concentration. This instrument can be simultaneous and/or sequential. Typical parameters and operating
conditions for the spectrometer are given in Table B.2.
Table B.2 - Typical parameters and operating conditions of the spectrometer
Parameter Unit Specifications
Type monochromator or/and polychromator
Argon humidifier (water) Yes
Argon (B.1.3.6) flows :
 plasma
l/min 12 to 15
 auxiliary
l/min» 1,5
 nebulizer
l/min» 0,7
Sample flow ml/min» 1,5
RF power W 1 000 to 1 250
Integration time : s
 simultaneous measurement
 sequential measurement
B.1.5 Procedure
B.1.5.1 Test portion
Weigh, to the nearest 0,1 g, about 10 g of the laboratory sample (m).
B.1.5.2 Test solution
Transfer the test portion (B.1.5.1) and water to a 100 ml volumetric flask and stir to dissolve. Add 1 ml nitric acid
(B.1.3.), [5 ml of scandium solution (B.1.3.4)], make up to the mark with water and mix.
B.1.5.3 Calibration and verification solutions
Transfer 40 ml of sodium chloride solution (B.1.3.3), 1 ml of nitric acid (B.1.3.1), [5 ml of scandium solution
(B.1.3.4)] and the volumes of mono-element solution (B.1.3.5) given in the Table B.3 to a series of 100 ml one-
mark volumetric flasks. Make up to the mark with water and mix.
Table B.3 - Calibration solutions for the different elements
Calibration solution Mono-element Corresponding concentration
solution
(As, Cd, Cr, Ni, Pb, Sb, Se)
ml mg/l
N°
a
1 00
b
2 0,250 2,50
3 0,500 5,00
c
4 0,500 5,00
a
Blank calibration solution.
b
Linearity verification solution.
c
Control solution prepared with different pipettes, flasks and if possible with different stock
solutions.
B.1.5.4 Determination
B.1.5.4.1 Preparation of the apparatus
Set all instrument parameters of the optical emission spectrometer (B.1.4.1) in accordance with the operating
manual of the instrument's manufacturer.
Prepare the analytical procedure including the lines shown in the Table B.4, with background correction,
concentrations of calibration solutions 1 and 3 described in (B.1.5.3) [and applying the reference technique].
Table B.4 - Wavelength per element
Element Wavelength
nm
line background
As 189,082
193,759
Cd 214,438
228,802
Cr 267,716
Ni 221,647 to be determined with
Pb 168,220 each instrument
Sb 217,581
Se 196,026
Sc 424,683
(internal standard) or
361,384
B.1.5.4.2 Spectrometric measurements
Repeat the measurements for at least five integration periods.
Rinse with the blank calibration solution (solution1) after each solution.
Calibrate the instrument with the calibration solutions 1 and 3 (B.1.5.3).
Control and check the linearity of the calibration curve by measurement of the following calibration solutions
(B.1.5.3) considered as unknown solutions :
 solution 3 ;
 solution 1 ;
 solution 1 ;
 solution 2 ;
 solution 4 ;
 solution 3.
Continue the measurements in the following order :
 solution 3 ;
 solution 1 ;
 solution 1 ;
 test solution (B.1.5.2) ;
 solution 3 ;
 solution 1 (B.1.5.3) ;
 solution 1 (B.1.5.3).
B.1.6 Expression of results
B.1.6.1 Evaluation
If necessary, correct for drift the results obtained with the test solution and control solutions 2 and 4 :
 for baseline drift by interpolating in time between both second measurements (the first can be
cross-contaminated) of the blank calibration solution (solution 1) ;
 for sensitivity drift by interpolating in time between the measurements of the solution 3.
NOTE Samples of unknown composition should be tested for the presence of matrix effects caused by present
components other than sodium chloride, by the analyte addition technique.
B.1.6.2 Calculation
The element content of the sample, c(element) in milligrams per kilogram of sodium chloride is given by the
following equation :
c()element =·c
m
where
m is the mass in grams of the test portion (B.1.5.1) ;
c is the corrected concentration of element, in milligrams per litre, in the test solution (B.1.5.2).
B.1.6.3 Repeatability and reproducibility
Analyses, carried out on some samples (enriched or not) by several laboratories, have given the following
statistical results, each laboratory having furnished results obtained by the same operator performing three
analyses per sample :
Table B.5 – Repeatability and reproducibility
Element P s s
c(element) r R
As 0,22 11 0,30 0,52
2,06 15 0,25 0,49
5,1 15 0,21 0,46
Cd 0,08 9 0,12 0,19
1,0 14 0,05 0,10
5,1 14 0,11 0,42
Cr - 0,01 8 0,02 0,07
0,97 12 0,03 0,1
5,0 12 0,08 0,22
Pb 0,18 9 0,79 0,79
2,0 13 0,41 0,60
4,8 14 0,65 0,72
Ni - 0,11 8 0,07 0,33
0,93 13 0,06 0,27
5,0 14 0,10 0,36
Sb 0,02 4 0,25 0,25
1,9 6 0,42 0,53
5,5 7 0,58 2,1
Se 0,06 7 0,17 0,21
1,9 10 0,23 0,27
4,9 11 0,27 0,28
where
c()élément is the element content (mean value), in milligrams per kilogram of sodium chloride ;
P is the number of laboratories retained after eliminating outliers ;
s is the repeatability standard deviation, in mg of element/kg ;
r
s is the reproducibility standard deviation, in mg of element/kg.
R
B.2 Determination of total mercury (cold vapour atomic absorption spectrometry)
B.2.1 General
The method applies to products of mercury content (Hg) equal to or greater than 20 μg/kg.
NOTE The lower limit of quantification, as stated here, can only be achieved if the procedure is carried out under optimum
conditions :
 skilled operators experienced with this method ;
 clean glassware, only used for such determination ;
 optimum apparatus settings ;
 very low mercury level of the ambient air ;
 high purity reagents.
B.2.2 Principle
Dissolution of the sample with a mixture of water, sodium chlorate and hydrochloric acid.
Oxidation with the nascent chlorine, converting all forms of mercury to ionic mercury (II).
Reduction of the excess of oxidant by hydroxylamine hydrochloride and of mercury (II) to atomic mercury by tin (II)
chloride.
Entrainment of the mercury in a stream of gas and measurement of the absorbance at a wavelength of 253,7 nm.
B.2.3 Reagents
All reagents shall be of recognized analytical grade having the lowest possible mercury content and the water used
shall conform to grade 3 in accordance with EN ISO 3696.
Store all reagents in glass bottles.
B.2.3.1 Sodium chloride with a mercury content less than 20 μg/kg.
B.2.3.2 Hydrochloric acid, c(HCl) » 6 mol/l (azeotropic mixture)
Purify this solution as follows.
Add 500 ml of water and 5 ml of sulfuric acid density r » 1,84 g/ml, 96 % (m/m) solution to 500 ml of hydrochloric
acid density r » 1,19 g/ml, 37 % (m/m) solution. Distill the azeotropic mixture.
B.2.3.3 Sodium chlorate (NaClO ), approximately 100 g/l solution.
B.2.3.4 Potassium dichromate (K2Cr2O7), approximately 4 g/l solution
Dissolve 4 g of potassium dichromate with 500 ml of water. Add 500 ml of nitric acid r » 1,40 g/ml, 65 % (m/m)
solution and mix.
B.2.3.5 Tin(II) chloride (SnCl .2H O), approximately 100 g/l solution
2 2
Dissolve 25 g of tin (II) chloride dihydrate with 50 ml of warm hydrochloric acid r » 1,19 g/ml, 37 % (m/m) solution.
Allow to cool and add 1 g to 2 g of metallic tin. Dilute to 250 ml with water and mix. Prepare this solution just before
use and slowly pass nitrogen through during 30 min to remove the mercury.
Ensure that oxidation of solid tin (II) chloride by air is prevented.
B.2.3.6 Hydroxylamine hydrochloride (NH OH.HCl), approximately 100 g/l solution.
B.2.3.7 Mercury, stock standard solution (I), c = 1000 mg/l, commercial standard solution or to be
(Hg)
prepared as follows :
 dissolve 1,354 g of mercury (II) chloride (HgCl ) with 50 ml of hydrochloric acid solution (B.2.3.2) and add
50 ml of potassium dichromate solution (B.2.3.4). Transfer to a 1 000 ml volumetric flask, dilute to the mark
with water and mix.
 store this solution in a cool, dark place and renew after two months.
B.2.3.8 Mercury, standard solution (II), c = 1 mg/l
(Hg)
Prepare this solution just before use by successive dilutions of the stock standard solution (I) (B.2.3.7). Add 50 ml
of potassium dichromate solution (B.2.3.4) for preparing 1000 ml of final solution.
B.2.3.9 Air or nitrogen
Use a gas containing no mercury or other components capable to provide absorbing radiations at a wavelength of
253,7 nm.
NOTE Any mercury present should be removed by a charcoal filter.
B.2.4 Apparatus
Ordinary laboratory apparatus and glassware.
NOTE All new glassware used for this determination, including flasks used for reagents or samples should be washed as
follows and thoroughly rinsed with water after each operation :
 with a brush and detergent if the walls are greasy ;
 with dilute nitric acid c(HNO ) » 7 mol/l.

The glassware should be checked by carrying out several blank tests until satisfactory results are obtained before using it for
actual determinations. Thereafter such glassware should be used for mercury determination only.
B.2.4.1 Apparatus allowing the determination of mercury
An example of suitable apparatus is shown in the Figure B.1. This applies to an open-circuit measuring system and
comprises principally the following :
B.2.4.1.1 Atomic absorption spectrometer
B.2.4.1.2 Mercury hollow cathode lamp or,
B.2.4.1.3 Low-pressure mercury vapour lamp
B.2.4.1.4 Measuring cell, minimum path length 10 cm with windows transparent to radiation of 253,7 nm.
B.2.4.1.5 Reaction vessel
Use, for example, a 100 ml gas washing bottle with sintered glass inlet or pointed immersion tube and 60 ml mark.
Fill the bottle with water when not in use.
If different bottles are used, check that the results are identical.
Traces of tin (IV) oxide which can have settled onto the walls shall be removed by hydrochloric acid r » 1,19 g/ml,
37 % (m/m) solution.
B.2.5 Procedure
B.2.5.1 Test portion
Weigh, to the nearest 0,1 g, about 10 g (m ) of the laboratory sample.
B.2.5.2 Test solution
Transfer the test portion (B.2.5.1) to a 100 ml conical flask and add 30 ml of water.
NOTE The test solutions should be not prepared in accordance with ISO 2479 because mercury losses can occur in those
solutions.
B.2.5.3 Blank test solution
Transfer 30 ml of water to a 100 ml conical flask.
B.2.5.4 Calibration solutions
To take into account the influence of sodium chloride on mercury evolution, take a quantity of sodium chloride
equal to the test portion (B.2.5.1) for the preparation of calibration solutions.
Transfer 10 g of sodium chloride (B.2.3.1), 30 ml of water and the volumes of mercury standard
solution (II) (B.2.3.8) given in Table B.6 to a series of 100 ml conical flasks.
Table B.6 - Calibration solutions for mercury
Calibration solution Corresponding mass
Mercury standard solution (II)
of mercury
N°
μg
ml
a
20,5 0,5
31,0 1,0
41,5 1,5
52,0 2,0
63,0 3,0
a
Zero calibration solution
B.2.5.5 Determination
B.2.5.5.1 Mineralization
Proceed as follows with the conical flasks prepared in B.2.5.2, B.2.5.3 and B.2.5.4.
Add some glass beads, 4 ml of hydrochloric acid (B.2.3.2) and 3 ml of sodium chlorate solution (B.2.3.3). Heat and
keep boiling for 5 min.
Allow to cool and transfer quantitatively to a 100 ml volumetric flask. Dilute to the mark with water and mix.
B.2.5.5.2 Preparation of the apparatus
Equip the spectrometer (B.2.4.1.1) with the mercury lamp (B.2.4.1.2 or B.2.4.1.3). Set the lamp current, the slit and
the flow of air or nitrogen according to the instruction manual of the instrument. Adjust the wavelength at the
maximum of emission at about 253,7 nm.
B.2.5.5.3 Spectrometric measurements
A maximum signal is obtained only under optimum conditions. For instance, the gas flow and the waiting time
between tin (II) chloride addition and start of stripping have great influence on the peak height. A typical waiting
time will be in the order of 5 min. Therefore those parameters shall be established experimentally for any individual
apparatus and matrix.
The maximum absorbance also depends very strongly upon the temperature of the solution during aeration
(A = 3 % per degree Celsius at room temperature). Therefore, all solutions shall be at the same temperature.
Test and blank solutions shall be analysed at the same time and with the same reagents.
Proceed with the solutions prepared in B.2.5.5.1 in the following way.
 Transfer 10,0 ml of solution (B.2.5.5.1) and 3,0 ml of hydroxylamine hydrochloride solution (B.2.3.6) to the
reaction vessel (B.2.4.1.5).
 Fill to the mark (60 ml) with water, add 2 ml of tin (II) chloride solution (B.2.3.5) and place the flask (B.2.4.1.5)
immediately into the apparatus system (B.2.4.1).
 Swirl to mix and allow to stand for a few minutes.
 Pass air or nitrogen through the reaction vessel and determine the maximum of absorbance. Stop the gas
flow and remove the reaction vessel.
 Wash the vessel with potassium dichromate solution (B.2.3.4) to oxidize any traces of tin (II) and rinse
thoroughly with water.
NOTE Samples of unknown composition should be tested for the presence of matrix effects, caused by present
components other than sodium chloride, by the analyte addition technique.
B.2.5.5.4 Calibration curve
Subtract the absorbance of the zero calibration solution from that of each other calibration solution (B.2.5.4) and
plot a graph with the masses of mercury (Hg), in micrograms, used to prepare the calibration solutions on the
abscissa and the corresponding corrected absorbances on the ordinate.
B.2.6 Expression of results
B.2.6.1 Calculation
The mercury content of the sample, c()Hg , in micrograms per kilogram of sodium chloride is given by the following
equation :
1 000
c()Hg = ()-m m
3 2
m
where
m is the mass, in grams, of the test portion (B.2.5.1) ;
m is the mass of mercury (Hg), in micrograms, corresponding to the absorbance obtained in B.2.5.5.3 for
the blank test solution.
m is the mass of mercury (Hg), in micrograms, corresponding to the absorbance obtained in B.2.5.5.3 for
the test solution ;
B.2.6.2 Repeatability and reproducibility
Analyses, carried out on three samples by several laboratories, have given the following statistical results, each
laboratory having furnished results obtained by the same operator performing two analyses per sample :
Table B.7 - Repeatability and reproducibility
Rock salt Evaporated salt Sea salt
Number of laboratories 14 12 12
Results, Hg in μg/kg
a a a
Mean
< LOQ < LOQ < LOQ
Standard deviation for :
 repeatability (s )
3,98 2,78 3,12
r
 reproducibility (s )
24,10 11,42 15,98
R
a
LOQ = Limit of quantification.
Key
A Atomic absorption spectrometer or mercury vapour meter
B Mercury hollow cathode lamp or low-pressure mercury vapour lamp
C Recorder or maximum deflection indicator
D Measuring cell
E Reaction vessel with sintered glass inlet or pointed immersion tube
F Four-way stopcock
G Flow control system (e.g. pressure regulator, needle valve and flow meter)
H Absorption tube with charcoal
I Absorption tube with drying agent
Figure B.1 - Determination of mercury by atomic absorption spectrometry - Typical apparatus
B.3 Determination of water-soluble hexacyanoferrate (II) (molecular absorption
spectrometry)
B.3.1 General
This method is applicable to products with an hexacyanoferrate (II) content, expressed as [K Fe(CN) ] of :
4 6
 2,5 mg/kg to 40 mg/kg when using the direct method ;
 0,25 mg/kg to 4 mg/kg when using the filtration method.
B.3.2 Principle
Ferrocyanide [hexacyanoferrate (II)] and iron (II) form in acid solution, the iron(II) hexacyanoferrate (II) complex
[Fe(CN) ] Prussian Blue.
which, in presence of iron(III) oxidizes immediately to iron (III) hexacyanoferrate Fe
4 6 3
The absorbance of this complex is measured at a wavelength around 700 nm.
The Prussian Blue can be filtered on a membrane filter. After redissolution with potassium hydroxide, the Prussian
Blue is reformed in a greatly reduced volume.
B.3.3 Reagents
All reagents shall be of recognized analytical grade and the water used shall conform to grade 3 in accordance with
EN ISO 3696.
B.3.3.1 Sodium chloride, hexacyanoferrate-free.
B.3.3.2 Sulfuric acid solution, c(H2SO4) » 0,5 mol/l.
B.3.3.3 Potassium hydroxide solution, c(KOH) » 0,05 mol/l.
B.3.3.4 Fe(II) - Fe(III) solution
Add 200 g of ammonium iron (II) sulfate [(NH ) SO . FeSO . 6H O] and 25 g of ammonium iron (III) sulfate
4 2 4 4
[(NH ) SO . Fe (SO ) 24H O] into a 1 000 ml volumetric flask. Dissolve with water, add 100 ml of sulfuric acid
4 2 4 2 4 3. 2
solution (B.3.3.2), dilute to the mark and mix.
Filter the solution and store in a dark bottle.
B.3.3.5 Potassium hexacyanoferrate (II), stock standard solution (I), c(K [Fe(CN) ]. 3H O) = 1,000 g/l.
4 6 2
Transfer 1,000 g of potassium hexacyanoferrate (II) K [Fe(CN) ]. 3H O to a 1000 ml volumetric flask. Dissolve with
4 6 2
water, add 5 ml of potassium hydroxide solution (B.3.3.3), dilute to the mark and mix.
Store in a dark bottle for a maximum of one month.
B.3.3.6 Potassium hexacyanoferrate (II), standard solution (II), c(K [Fe(CN) ]. 3H O) = 50,0 mg/l.
4 6 2
Transfer 50,0 ml of the stock solution (I) (B.3.3.5) and 5 ml of potassium hydroxide solution (B.3.3.3) to a 1 000 ml
volumetric flask. Dilute to the mark and mix.
Prepare this solution just before use.
B.3.4 Apparatus
Ordinary laboratory apparatus and glassware together with the following.
B.3.4.1 Spectrometer or,
B.3.4.2 Photocolorimeter, fitted with a filter ensuring maximum transmission between 690 nm and 710 nm.
NOTE The type of apparatus used (spectrometer or photocolorimeter), the path length and the wavelength (or type of filter)
should be specified.
B.3.4.3 Membrane filter about 50 mm diameter, 0,3 μm maximum porosity.
B.3.5 Procedure
B.3.5.1 Test portion
Weigh, to the nearest 0,1 g, about 100 g (m) of the laboratory sample.
B.3.5.2 Test solution
Transfer the test portion (B.3.5.1) and water to a
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