SIST ISO 13658:2001

Zinc sulfide concentrates -- Determination of zinc content -- Hydroxide precipitation and EDTA titrimetric method

This International Standard specifies a hydroxide precipitation and EDTA titrimetric method for the determination of
the zinc content of zinc ores and concentrates containing 10 % (m/m) to 60%(m/m) zinc.

Concentrés sulfurés de zinc -- Dosage du zinc -- Méthode par précipitation d'hydroxydes et titrage à l'EDTA

Koncentrati cinkovega sulfida - Določevanje cinka - Hidroksidna sedimentacija in titrimetrijska metoda z EDTA

General Information

• Status: Published
• Publication Date: 31-May-2001
• ICS: 73.060.99 - Other metalliferous minerals
• Technical Committee: IRUD - Mining
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jun-2001
• Due Date: 01-Jun-2001
• Completion Date: 01-Jun-2001
• Ref Project: ISO 13658:2000 - Zinc sulfide concentrates — Determination of zinc content — Hydroxide precipitation and EDTA titrimetric method

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 13658
First edition
2000-03-15
Zinc sulfide concentrates — Determination
of zinc content — Hydroxide precipitation
and EDTA titrimetric method
Concentrés sulfurés de zinc — Dosage du zinc — Méthode par
précipitation d'hydroxydes et titrage à l'EDTA
Reference number
ISO 13658:2000(E)
©
ISO 2000

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ISO 13658:2000(E)
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ISO 13658:2000(E)
Contents Page
Foreword.iv
1 Scope .1
2 Normative references .1
3 Principle.2
4 Reagents.2
5 Apparatus .3
6 Sample .3
7 Procedure .4
8 Expression of results .6
9 Application to the trading of zinc concentrates .7
10 Accuracy.7
11 Test report .8
Annex A (informative) An examination of potentially interfering elements .9
Annex B (normative) Procedure for the preparation and determination of the mass of a predried test
portion.10
Annex C (normative) Determination of zinc content of acid-insoluble and hydroxide precipitation
residues by atomic absorption spectroscopy.12
Annex D (normative) Determination of cadmium by atomic absorption spectrometry.15
Annex E (normative) Flowsheet of the procedure for the acceptance of analytical values for test
samples.18
Annex F (informative) Derivation of precision equations .19
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ISO 13658:2000(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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 13658 was prepared by Technical Committee ISO/TC 183, Copper, lead and zinc ores
and concentrates.
Annexes B, C, D and E form a normative part of this International Standard. Annexes A and F are for information
only.
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INTERNATIONAL STANDARD ISO 13658:2000(E)
Zinc sulfide concentrates — Determination of zinc content —
Hydroxide precipitation and EDTA titrimetric method
WARNING — This International Standard may involve hazardous materials, operations and equipment. It is
the responsibility of the user of this International Standard to establish appropriate health and safety
practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies a hydroxide precipitation and EDTA titrimetric method for the determination of
the zinc content of zinc ores and concentrates containing 10 % (m/m)to 60% (m/m)zinc.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 385-1:1984, Laboratory glassware — Burettes — Part 1: General requirements.
ISO 648:1977, Laboratory glassware — One-mark pipettes.
ISO 1042:1998, Laboratory glassware — One-mark volumetric flasks.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods.
ISO 4787:1984, Laboratory glassware — Volumetric glassware — Methods for use and testing of capacity.
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method
for the determination of repeatability and reproducibility of a standard measurement method.
ISO 9599:1991, Copper, lead and zinc sulfide concentrates — Determination of hygroscopic moisture in the
analysis sample — Gravimetric method.
ISO 12739:1997, Zinc sulfide concentrates — Determination of zinc content — Ion-exchange/EDTA titrimetric
method.
ISO 13291:1997, Zinc sulfide concentrates — Determination of zinc content — Solvent extraction and EDTA
titrimetric method.
ISO/Guide 35:1989, Certification of reference materials — General and statistical principles.
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ISO 13658:2000(E)
3Principle
Dissolution of a test portion of zinc concentrate in bromine and nitric acid. Dissolution of any remaining insoluble
residue in hydrofluoric and sulfuric acids. Separation of aluminium, iron and manganese as hydroxides using
precipitation with ammonia, ammonium chloride and ammonium persulfate. Separation of lead as sulfate. Copper is
masked. Determination of zinc and cadmium together by complexometric titration (pH 5,5 to 5,7) in the presence of
xylenol orange. Independent determination of cadmium and subtraction from the zinc value.
NOTE An examination of potential interfering elements is contained in annex A.
4 Reagents
During the analysis, use only reagents of recognized analytical reagent grade and water that complies with grade 2
of ISO 3696.
4.1 Zinc metal, minimum purity 99,99 %
The surface of the metal shall be free from oxide prior to use and may be cleaned by immersing the metal in
hydrochloric acid (4.6) for 1 min, washing well with water followed by an acetone rinse and dried in an oven at
50 �C.
4.2 Ammonium chloride
4.3 Bromine
4.4 Nitric acid (� 1,42 g/ml)
20
4.5 Hydrochloric acid (� 1,16 g/ml to 1,19 g/ml)
20
4.6 Hydrochloric acid (1+1)
Add 500 ml of hydrochloric acid (4.5) to 500 ml of water.
4.7 Sulfuric acid (� 1,84 g/ml)
20
4.8 Dilute sulfuric acid (1+1)
Add carefully and slowly with stirring, 500 ml of sulfuric acid (4.7) to 500 ml of water.
4.9 Sulfuric acid (1 + 99)
Add 20 ml of sulfuric acid (4.8) to 1 000 ml of water.
4.10 Ammonia (� 0,89 g/ml)
20
4.11 Ammonium persulfate
4.12 Ammonia washing solution
Dissolve 20 g of ammonium chloride in 1 000 ml of aqueous ammonia solution (1 + 100).
4.13 Ethanol, pure or denatured
4.14 Acetic acid (� 1,05 g/ml)
20
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ISO 13658:2000(E)
4.15 Bromothymol blue indicator solution (1 g/l)
Dissolve 0,1 g of bromothymol blue in ethanol (4.13) and dilute to 100 ml.
4.16 Hexamethylenetetramine buffer solution (250 g/l)
Dissolve 250 g of hexamethylenetetramine (hexamine) in water. Add 60 ml of acetic acid (4.14) and dilute to 1 l.
4.17 Masking solution
Dissolve 50 g of ammonium fluoride and 100 g of sodium thiosulfate pentahydrate in water and dilute to 1 l.
4.18 Xylenol orange indicator solution (1 g/l)
Dissolve0,1gofthesodium saltofxylenolorangeinwateranddiluteto100ml.
4.19 Iron(III) solution (10mgFe/ml)
Dissolve 72,3 g of iron(III) nitrate nonahydrate in water and dilute to 1 l.
4.20 EDTA standard solution (0,1 mol/l)
Dissolve 37,2 g of the di-sodium salt of ethylenediaminetetraacetic acid and 2 g of sodium hydroxide in water and
dilute to 1 l.
5 Apparatus
5.1 Class A volumetric glassware, complying with ISO 385-1, ISO 648 and ISO 1042 and used in accordance
with ISO 4787.
5.2 Balance, capable of being read to 0,1 mg.
5.3 Laboratory hotplate
5.4 pH meter
6Sample
6.1 Test sample
Prepare an air-equilibrated test sample in accordance with ISO 9599.
NOTE An air-equilibrated test sample is not required if predried test portions are to be used (see annex B).
6.2 Test portion
Taking multiple increments, extract a test portion of 0,5 g from the test sample and weigh to the nearest 0,1 mg. At
the same time as the test portions are taken for analysis, weigh test portions for the determination of hygroscopic
moisture in accordance with ISO 9599. Alternatively, the method specified in annex B may be used to prepare
predried test portions directly from the laboratory sample.
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ISO 13658:2000(E)
7 Procedure
7.1 Number of determinations
Carry out the determinations at least in duplicate, as far as possible under repeatability conditions, on each test
sample.
NOTE Repeatability conditions exist where mutually independent test results are obtained with the same method on
identical test material in the same laboratory by the same operator using the same equipment within short intervals of time.
7.2 Reagent blank
A reagent blank shall be determined. It is advisable to perform duplicate blank determinations every time an
analysis is carried out on a laboratory sample. The blank samples are carried through the whole procedure, with
the exception that no laboratory sample test portion is required. The average volume of EDTA titrant used for the
reagent blanks is V .
b
7.3 Dissolution
Digest the sample as follows.
Transfer the test portion (6.2) to a 300 ml conical beaker. Moisten the material with about 5 ml of water and add
1 ml of bromine (4.3). Stand for 15 min, swirling the beaker and contents from time to time.
Cautiously add 15 ml of nitric acid (4.4). Place the beaker on a hotplate (5.3) and heat gradually until bromine and
nitrogen oxides are expelled. Add 15 ml of sulfuric acid (4.8). Heat and evaporate the solution until the evolution of
sulfuric acid fumes (approximately 5 ml).
NOTE Care needs to be taken to ensure no loss of material when fuming samples containing significant carbonaceous
material, due to the sample climbing up the walls of the beaker.
Cool and cautiously add about 50 ml of water and heat the solution until boiling. Cool the solution to room
temperature and filter it into a 500 ml conical beaker through a medium-speed cellulose filter paper. Wash the
beaker and filter paper thoroughly with sulfuric acid (4.9). Collect the filtrate and washing solution in the same
beaker.
Reserve the filter paper and acid-insoluble residue for determination of zinc by FAAS (as described in annex C) for
the concentrate being analysed and the analyst performing the test, unless it has been statistically shown, by
previous testing, that the zinc is completely soluble in the initial decomposition. If this step is not routinely
performed, regular checks confirming the validity of its exclusion shall be carried out for each concentrate type by
each analyst. Similarly, all documentation containing results where this step has been excluded shall contain a
comment indicating this fact.
7.4 Separation of aluminium, iron and manganese as hydroxides
Add 15 g of ammonium chloride (4.2) to the solution and swirl gently to dissolve.
NOTE 1 If the iron content of the sample is only a few percent, then iron(III) solution (4.19) is added to the solution to
increase the contained iron in solution to about 50 mg.
Heat to near boiling then add ammonia (4.10) to the solution until complete precipitation occurs and then 30 ml in
excess. Add 1 g of ammonium persulfate (4.11) to the solution, heat until boiling and continue boiling for 1 min.
Stand to allow the precipitate to settle out. Filter into another 500 ml beaker through a medium-speed cellulose filter
paper and wash the precipitate several times with hot ammonia washing solution (4.12). Collect the filtrate and the
washing solutions in the same beaker.
NOTE 2 Filtration will be slow for high lead content samples.
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ISO 13658:2000(E)
Wash the precipitate back into the original beaker without damaging the filter paper and dissolve it with 10 ml of
hydrochloric acid (4.6). Add 5 g of ammonium chloride (4.2) to the solution. Repeat the precipitation by addition of
ammonia (4.10) and ammonium persulfate (4.11). Boil, filter through the original filter paper and wash in the same
manner as described above.
Collect the filtrate and washing solution in the same beaker used to collect the filtrate for the first separation and
place the beaker on a hotplate (5.3). Heat gently and evaporate the solution to about 200 ml. Cool to room
temperature.
Keep the hydroxide precipitate for later treatment.
7.5 Titration
7.5.1 Determination of the titration factor of the EDTA solution
NOTE 1 In order to obtain a relative accuracy of between 0,1 % and 0,2 %, it is necessary to standardize the EDTA solution
with zinc at the same time and under the same conditions as the analysis. It is thus advisable for the calibration to follow the
complete set of operating conditions set down for the analysis. Likewise, to improve the repeatability of the calibration, it is
useful to prepare several zinc reference solutions.
The EDTA solution should be standardized as follows:
Weigh into three separate 500 ml beakers between 0,055 g and 0,31 g of high-purity zinc metal (4.1), to the
nearest 0,1 mg, depending on the zinc content of the test sample. Record these masses as m , m and m .
1 2 3
Add 10 ml of hydrochloric acid (4.6) and warm gently to aid the complete dissolution of the metal. Add 50 ml of
water and 20 g of ammonium chloride (4.2), swirl gently to dissolve and dilute to about 200 ml with water.
Add 4 drops of bromothymol blue indicator solution (4.15) and neutralize by adding ammonia (4.10) dropwise until
the yellow colour disappears. Add 7 drops of hydrochloric acid (4.5).
NOTE 2 A pH meter (5.4) may be used to adjust the pH to a value of 5,6 instead of using the bromothymol blue indicator.
Care should be taken to ensure that the electrodes are washed off with water before continuing the procedure.
Add 20 ml of hexamethylenetetramine buffer solution (4.16) and 20 ml of masking solution (4.17). Add 10 drops of
xylenol orange indicator (4.18) to the solution. Swirl to dissolve and titrate with EDTA standard solution (4.20) until
a colour change to yellow occurs. Record the volumes as V , V and V .
1 2 3
Calculate the intermediate factors, fi , for each beaker using the following equation:
x
fi = m /V for x =1 to 3 (1a)
x x x
where
fi is the factor obtained from the titration;
x
m is the mass of zinc weighed, in grams;
x
V is the volume of EDTA solution, in millilitres.
x
If the range of values for fi , fi and fi exceeds 0,000 01 g/ml, then repeat the standardization.
1 2 3
Otherwise calculate the mean factor as follows:
f=(fi +fi +fi )/3 (1b)
1 2 3
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ISO 13658:2000(E)
7.5.2 Titration of samples
To the sample prepared in 7.4, add 4 drops of bromothymol blue indicator solution (4.15) and neutralize by adding
hydrochloric acid (4.5) dropwise until the blue colour disappears. Add 7 drops in excess.
NOTE 1 A pH meter (5.4) may be used to adjust the pH to a value of 5,6 instead of using the bromothymol blue indicator.
Care should be taken to ensure that the electrodes are washed off with water before continuing the procedure.
Add 20 ml of hexamethylenetetramine buffer solution (4.16) and 20 ml of masking solution (4.17). Add 10 drops of
xylenol orange indicator (4.18) to the solution. Swirl to dissolve and titrate with EDTA standard solution (4.20) until
a colour change to yellow occurs. Record the volume of titrant used as V .
t
NOTE 2 If the test sample contains cadmium, it will not be removed during the procedure given in 7.5. The cadmium
concentration is determined separately and a correction made for its presence. The method for the determination of cadmium is
given in annex D.
7.6 Determination of mass of zinc in the acid-insoluble residue and hydroxide precipitate
Determine the mass of zinc (m ) contained in both the acid-insoluble residue from the dissolution step (7.3) and
Zn
the hydroxide precipitate from the separation step (7.4) as described in annex C.
7.7 Determination of the cadmium content of the sample
Determine the cadmium content C of the sample as described in annex D.
Cd
8 Expression of results
8.1 Calculation of the zinc content of the test portions
LVV��f�m O
bg
100
tb Zn
Zn%,� ��100 � 0 581C (2)
M P
Cd
mH100�
M P
N Q
where
V is the volume of EDTA used to titrate the sample aliquot, in millilitres;
t
V is the volume of EDTA used to titrate the reagent blank, in millilitres;
b
f is the zinc equivalent factor of the EDTA solution, in grams per millilitre;
m is the mass of zinc in the residues as determined in annex C, in grams;
Zn
m is the test portion mass, in grams;
H is the hygroscopic moisture of the test portion, expressed as a percentage by mass;
C is the cadmium concentration as determined in annex D, expressed as a percentage by mass.
Cd
NOTE In the case of a predried test portion, H is equal to zero.
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ISO 13658:2000(E)
8.2 Calculation of the zinc content of the test sample
Process the duplicate test portion results for the test sample as per the chart in annex E. If necessary, analyse
extra test portions as required by annex E.
NOTE The replicate limit is calculated as follows:
2
Replicate limit = 2,8�(2s )=0,16
r
where s is the repeatability standard deviation, in percent (see 10.1)
r
9 Application to the trading of zinc concentrates
Between-laboratory precision is used to determine the agreement between the results reported by two laboratories.
The assumption is that both laboratories followed the same procedure.
Calculate the following quantities:
Critical difference R =0,34
Range E =�μ � μ �
1 2
where
μ is the final result, in percent, reported by laboratory 1;
1
μ is the final result, in percent, reported by laboratory 2.
2
NOTE The critical difference is one of the factors used to derive the splitting limit.
If Eu R, the results are in agreement and the average of the two results can be used for commercial purposes.
10 Accuracy
10.1 Expression of precision
The precision of this analytical method is expressed by the following equations:
NOTE Additional information is given in annex F.
s =0,041
r
s =0,12
R
where
s is the repeatability standard deviation, in percent;
r
s is the reproducibility standard deviation, in percent.
R
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ISO 13658:2000(E)
10.2 Check of trueness
The trueness of the analytical method can be checked by applying it to a certified reference material (CRM). When
the precision has been confirmed, the final laboratory result can be compared with the certified value, A . There are
c
two possibilities as follows:
�μ � A �u C (3)
c c
If this condition exists, the difference between the reported result and the certified value is statistically insignificant.
�μ � A � > C (4)
c c
If this condition exists, the difference between the reported result and the certified value is statistically significant.
Where
μ is the final result, in percent, of the certified reference material;
c
A is the certified value, in percent, of the certified reference material;
c
C is a quantity, in percent, depending on the type of certified reference material used as defined in 10.2.1.
Reference materials used for this purpose shall be prepared and certified in accordance with ISO Guide 35.
If the reference material has been certified/characterized by an inter-laboratory test programme,
22* 2
Cs��21sbgn� /n�slAq (5)
Rr c
where
2
s {A } is the variance of the certified value;
c
n is the number of replicate determinations of the whole method.
If the reference material has been certified/characterized by only one laboratory,
22*
Cs��22 sn�2 /n (6)
bg
Rr
where n is the number of replicate determinations of the whole method.
NOTE It is recommended that this type of certified reference material be avoided unless the particular CRM is known to
have an unbiased certified value.
11 Test report
The test report shall contain the following information:
a) identification of the sample;
b) reference to this International Standard, i.e., ISO 13658;
c) zinc content of the sample, expressed as a percentage by mass;
d) date on which the test was carried out;
e) any occurrences noticed during the determination which may have had an influence on the results.
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ISO 13658:2000(E)
Annex A
(informative)
An examination of potentially interfering elements
A.1 Scope
This annex describes the effect of potentially interfering elements and how the interference is minimized within the
procedure.
A.2 Cadmium
Cadmium is not removed by precipitation. It is determined separately and the appropriate correction to the zinc
concentration is made (see 7.7).
A.3 Lead
Lead is commonly present in large quantities in zinc concentrates. It is largely precipitated as lead sulfate in the
dissolution stage (see 7.3). Small amounts of lead are completely eliminated in the filtration stage.
A.4 Iron and manganese
Iron and manganese are eliminated in the separation stage (see 7.4).
A.5 Copper
Copper is masked by the masking solution in the titration stage (see 7.5).
A.6 Nickel and cobalt
If the concentration of nickel and cobalt is less than 0,03 %, their influence is negligible. Levels above this value are
not known to exist in internationally traded concentrates.
A.7 Calcium and aluminium
Calcium is partially precipitated as calcium sulfate in the dissolution stage (see 7.3) and aluminium is largely
eliminated as a precipitate in the separation stage (see 7.4). Calcium and aluminium remaining in the filtrate are
masked during the titration stage (see 7.5)
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ISO 13658:2000(E)
Annex B
(normative)
Procedure for the preparation and determination of the mass of a predried
test portion
B.1 Scope
This annex sets out a method for the preparation and determination of the mass of a pre-dried test portion in the
analysis of zinc sulfide concentrates. The method is applicable to zinc sulfide concentrates not susceptible to
oxidation and having hygroscopic moisture contents ranging from 0,05 % (m/m)to2%(m/m).
B.2 Principle
Drying of the test portion to be used for analysis in air in an oven maintained at 105 °C ± 5 �C. Weighing of the
dried test portion and using it for the analysis. No correction for moisture is required.
B.3 Reagents
B.3.1 Desiccant, such as self-indicating silica gel or anhydrous magnesium perchlorate.
WARNING—Care should be taken when disposing of exhausted magnesium perchlorate. It should be
washed down the sink with a stream of running water.
B.4 Apparatus
B.4.1 Analytical balance, sensitive to 0,1 mg.
B.4.2 Weighing vessels, of glass or silica or corrosion-resistant metal having externally-fitting air-tight covers.
For small test portions (less than 3 g), the mass of the vessel should be as small as possible, i.e., less than 20 g.
B.4.3 Laboratory oven, capable of maintaining a temperature of 105 �C±5 �C.
B.5 Procedure
B.5.1 Preparation of the weighing vessel
Dry the weighing vessel and vessel cover (B.4.2) by heating in a laboratory oven (B.4.3) at 105 �C± 5 �Cfor 1h.
Transfer the vessel and vessel cover to a desiccator containing suitable fresh desiccant (B.3.1) and allow to cool to
ambient temperature.
B.5.2 Test portion
Tare the dried weighing vessel and vessel cover (B.4.2). Immediately add a portion of the laboratory sample to
provide a suitable predried test portion. An accurate total mass of the test portion and weighing vessel is not
required at this point.
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ISO 13658:2000(E)
B.5.3 Determination of the test portion dry mass
Transfer the uncovered weighing vessel and test portion and vessel cover to the laboratory oven (B.4.3) and dry at
105 �C � 5 �C for 2 h. After the 2 h period, remove the weighing vessel and dry test portion from the oven, replace
the vessel cover and allow to cool to ambient temperature in the desiccator. When cool, remove the weighing
vessel and dry test portion and vessel cover from the desiccator and weigh to the nearest 0,1 mg (m ) after slightly
1a
lifting the cover and quickly replacing it. Transfer the test portion to the appropriate analytical apparatus and
immediately re-weigh the empty weighing vessel and vessel cover. Record the mass to the nearest 0,1 mg (m ).
2
NOTE For new concentrates of unknown characteristics, it is advisable to repeat the drying for another 2 h at
105 �C � 5 �C and to re-weigh the weighing vessel and test portion plus vessel cover to the nearest 0,1 mg (m ). The test
1b
portion can be considered stable if the difference between m and m is within 0,5 mg. If this condition is not achieved, the
1a 1b
drying and weighing steps should be repeated.
B.6 Calculation of the test portion dry mass
The dry mass of the test portion (m ) is calculated from the equation:
3
m = m � m (B.1)
3 1a 2
where
m is the mass, in grams, of the dried test portion plus weighing vessel plus vessel cover;
1a
m is the mass, in grams, of the empty weighing vessel plus vessel cover;
2
m is the mass, in grams, of the dry test portion.
3
The mass of the dry test portion is the mass to be used to calculate the element concentration in the laboratory
sample on a dry basis. No correction for hygroscopic moisture is required.
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Concentrés sulfurés de zinc -- Dosage du zinc -- Méthode par précipitation d'hydroxydes et titrage à l'EDTAZinc sulfide concentrates -- Determination of zinc content -- Hydroxide precipitation and EDTA titrimetric method73.060.99Druge rudeOther metalliferous mineralsICS:Ta slovenski standard je istoveten z:ISO 13658:2000SIST ISO 13658:2001en01-junij-2001SIST ISO 13658:2001SLOVENSKI
STANDARD



SIST ISO 13658:2001



ReferencenumberISO13658:2000(E)©ISO2000INTERNATIONALSTANDARDISO13658Firstedition2000-03-15Zincsulfideconcentrates—Determinationofzinccontent—HydroxideprecipitationandEDTAtitrimetricmethodConcentréssulfurésdezinc—Dosageduzinc—Méthodeparprécipitationd'hydroxydesettitrageàl'EDTASIST ISO 13658:2001



ISO13658:2000(E)PDFdisclaimerThisPDFfilemaycontainembeddedtypefaces.InaccordancewithAdobe'slicensingpolicy,thisfilemaybeprintedorviewedbutshallnotbeeditedunlessthetypefaceswhichareembeddedarelicensedtoandinstalledonthecomputerperformingtheediting.Indownloadingthisfile,partiesacceptthereintheresponsibilityofnotinfringingAdobe'slicensingpolicy.TheISOCentralSecretariatacceptsnoliabilityinthisarea.AdobeisatrademarkofAdobeSystemsIncorporated.DetailsofthesoftwareproductsusedtocreatethisPDFfilecanbefoundintheGeneralInforelativetothefile;thePDF-creationparameterswereoptimizedforprinting.EverycarehasbeentakentoensurethatthefileissuitableforusebyISOmemberbodies.Intheunlikelyeventthataproblemrelatingtoitisfound,pleaseinformtheCentralSecretariatattheaddressgivenbelow.©ISO2000Allrightsreserved.Unlessotherwisespecified,nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromeitherISOattheaddressbeloworISO'smemberbodyinthecountryoftherequester.ISOcopyrightofficeCasepostal[e-mail]©ISO2000–AllrightsreservedSIST ISO 13658:2001



ISO13658:2000(E)©ISO2000–AllrightsreservediiiContentsPageForeword.iv1Scope.12Normativereferences.13Principle.24Reagents.25Apparatus.36Sample.37Procedure.48Expressionofresults.69Applicationtothetradingofzincconcentrates.710Accuracy.711Testreport.8AnnexA(informative)Anexaminationofpotentiallyinterferingelements.9AnnexB(normative)Procedureforthepreparationanddeterminationofthemassofapredriedtestportion.10AnnexC(normative)Determinationofzinccontentofacid-insolubleandhydroxideprecipitationresiduesbyatomicabsorptionspectroscopy.12AnnexD(normative)Determinationofcadmiumbyatomicabsorptionspectrometry.15AnnexE(normative)Flowsheetoftheprocedurefortheacceptanceofanalyticalvaluesfortestsamples.18AnnexF(informative)Derivationofprecisionequations.19SIST ISO 13658:2001



ISO13658:2000(E)iv©ISO2000–AllrightsreservedForewordISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISOmemberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnicalcommittees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhastherighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,inliaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnicalCommission(IEC)onallmattersofelectrotechnicalstandardization.InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part3.DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting.PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote.AttentionisdrawntothepossibilitythatsomeoftheelementsofthisInternationalStandardmaybethesubjectofpatentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.InternationalStandardISO13658waspreparedbyTechnicalCommitteeISO/TC183,Copper,leadandzincoresandconcentrates.AnnexesB,C,DandEformanormativepartofthisInternationalStandard.AnnexesAandFareforinformationonly.SIST ISO 13658:2001



INTERNATIONALSTANDARDISO13658:2000(E)©ISO2000–Allrightsreserved1Zincsulfideconcentrates—Determinationofzinccontent—HydroxideprecipitationandEDTAtitrimetricmethodWARNING—ThisInternationalStandardmayinvolvehazardousmaterials,operationsandequipment.ItistheresponsibilityoftheuserofthisInternationalStandardtoestablishappropriatehealthandsafetypracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.1ScopeThisInternationalStandardspecifiesahydroxideprecipitationandEDTAtitrimetricmethodforthedeterminationofthezinccontentofzincoresandconcentratescontaining10%(m/m)to60%(m/m)zinc.2NormativereferencesThefollowingnormativedocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthisInternationalStandard.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthesepublicationsdonotapply.However,partiestoagreementsbasedonthisInternationalStandardareencouragedtoinvestigatethepossibilityofapplyingthemostrecenteditionsofthenormativedocumentsindicatedbelow.Forundatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIECmaintainregistersofcurrentlyvalidInternationalStandards.ISO385-1:1984,Laboratoryglassware—Burettes—Part1:Generalrequirements.ISO648:1977,Laboratoryglassware—One-markpipettes.ISO1042:1998,Laboratoryglassware—One-markvolumetricflasks.ISO3696:1987,Waterforanalyticallaboratoryuse—Specificationandtestmethods.ISO4787:1984,Laboratoryglassware—Volumetricglassware—Methodsforuseandtestingofcapacity.ISO5725-2:1994,Accuracy(truenessandprecision)ofmeasurementmethodsandresults—Part2:Basicmethodforthedeterminationofrepeatabilityandreproducibilityofastandardmeasurementmethod.ISO9599:1991,Copper,leadandzincsulfideconcentrates—Determinationofhygroscopicmoistureintheanalysissample—Gravimetricmethod.ISO12739:1997,Zincsulfideconcentrates—Determinationofzinccontent—Ion-exchange/EDTAtitrimetricmethod.ISO13291:1997,Zincsulfideconcentrates—Determinationofzinccontent—SolventextractionandEDTAtitrimetricmethod.ISO/Guide35:1989,Certificationofreferencematerials—Generalandstatisticalprinciples.SIST ISO 13658:2001



ISO13658:2000(E)2©ISO2000–Allrightsreserved3PrincipleDissolutionofatestportionofzincconcentrateinbromineandnitricacid.Dissolutionofanyremaininginsolubleresidueinhydrofluoricandsulfuricacids.Separationofaluminium,ironandmanganeseashydroxidesusingprecipitationwithammonia,ammoniumchlorideandammoniumpersulfate.Separationofleadassulfate.Copperismasked.Determinationofzincandcadmiumtogetherbycomplexometrictitration(pH5,5to5,7)inthepresenceofxylenolorange.Independentdeterminationofcadmiumandsubtractionfromthezincvalue.NOTEAnexaminationofpotentialinterferingelementsiscontainedinannexA.4ReagentsDuringtheanalysis,useonlyreagentsofrecognizedanalyticalreagentgradeandwaterthatcomplieswithgrade2ofISO3696.4.1Zincmetal,minimumpurity99,99%Thesurfaceofthemetalshallbefreefromoxidepriortouseandmaybecleanedbyimmersingthemetalinhydrochloricacid(4.6)for1min,washingwellwithwaterfollowedbyanacetonerinseanddriedinanovenat50C.4.2Ammoniumchloride4.3Bromine4.4Nitricacid(201,42g/ml)4.5Hydrochloricacid(201,16g/mlto1,19g/ml)4.6Hydrochloricacid(1+1)Add500mlofhydrochloricacid(4.5)to500mlofwater.4.7Sulfuricacid(201,84g/ml)4.8Dilutesulfuricacid(1+1)Addcarefullyandslowlywithstirring,500mlofsulfuricacid(4.7)to500mlofwater.4.9Sulfuricacid(1+99)Add20mlofsulfuricacid(4.8)to1000mlofwater.4.10Ammonia(200,89g/ml)4.11Ammoniumpersulfate4.12AmmoniawashingsolutionDissolve20gofammoniumchloridein1000mlofaqueousammoniasolution(1+100).4.13Ethanol,pureordenatured4.14Aceticacid(201,05g/ml)SIST ISO 13658:2001



ISO13658:2000(E)©ISO2000–Allrightsreserved34.15Bromothymolblueindicatorsolution(1g/l)Dissolve0,1gofbromothymolblueinethanol(4.13)anddiluteto100ml.4.16Hexamethylenetetraminebuffersolution(250g/l)Dissolve250gofhexamethylenetetramine(hexamine)inwater.Add60mlofaceticacid(4.14)anddiluteto1l.4.17MaskingsolutionDissolve50gofammoniumfluorideand100gofsodiumthiosulfatepentahydrateinwateranddiluteto1l.4.18Xylenolorangeindicatorsolution(1g/l)Dissolve0,1gofthesodiumsaltofxylenolorangeinwateranddiluteto100ml.4.19Iron(III)solution(10mgFe/ml)Dissolve72,3gofiron(III)nitratenonahydrateinwateranddiluteto1l.4.20EDTAstandardsolution(0,1mol/l)Dissolve37,2gofthedi-sodiumsaltofethylenediaminetetraaceticacidand2gofsodiumhydroxideinwateranddiluteto1l.5Apparatus5.1ClassAvolumetricglassware,complyingwithISO385-1,ISO648andISO1042andusedinaccordancewithISO4787.5.2Balance,capableofbeingreadto0,1mg.5.3Laboratoryhotplate5.4pHmeter6Sample6.1TestsamplePrepareanair-equilibratedtestsampleinaccordancewithISO9599.NOTEAnair-equilibratedtestsampleisnotrequiredifpredriedtestportionsaretobeused(seeannexB).6.2TestportionTakingmultipleincrements,extractatestportionof0,5gfromthetestsampleandweightothenearest0,1mg.Atthesametimeasthetestportionsaretakenforanalysis,weightestportionsforthedeterminationofhygroscopicmoistureinaccordancewithISO9599.Alternatively,themethodspecifiedinannexBmaybeusedtopreparepredriedtestportionsdirectlyfromthelaboratorysample.SIST ISO 13658:2001



ISO13658:2000(E)4©ISO2000–Allrightsreserved7Procedure7.1NumberofdeterminationsCarryoutthedeterminationsatleastinduplicate,asfaraspossibleunderrepeatabilityconditions,oneachtestsample.NOTERepeatabilityconditionsexistwheremutuallyindependenttestresultsareobtainedwiththesamemethodonidenticaltestmaterialinthesamelaboratorybythesameoperatorusingthesameequipmentwithinshortintervalsoftime.7.2ReagentblankAreagentblankshallbedetermined.Itisadvisabletoperformduplicateblankdeterminationseverytimeananalysisiscarriedoutonalaboratorysample.Theblanksamplesarecarriedthroughthewholeprocedure,withtheexceptionthatnolaboratorysampletestportionisrequired.TheaveragevolumeofEDTAtitrantusedforthereagentblanksisVb.7.3DissolutionDigestthesampleasfollows.Transferthetestportion(6.2)toa300mlconicalbeaker.Moistenthematerialwithabout5mlofwaterandadd1mlofbromine(4.3).Standfor15min,swirlingthebeakerandcontentsfromtimetotime.Cautiouslyadd15mlofnitricacid(4.4).Placethebeakeronahotplate(5.3)andheatgraduallyuntilbromineandnitrogenoxidesareexpelled.Add15mlofsulfuricacid(4.8).Heatandevaporatethesolutionuntiltheevolutionofsulfuricacidfumes(approximately5ml).NOTECareneedstobetakentoensurenolossofmaterialwhenfumingsamplescontainingsignificantcarbonaceousmaterial,duetothesampleclimbingupthewallsofthebeaker.Coolandcautiouslyaddabout50mlofwaterandheatthesolutionuntilboiling.Coolthesolutiontoroomtemperatureandfilteritintoa500mlconicalbeakerthroughamedium-speedcellulosefilterpaper.Washthebeakerandfilterpaperthoroughlywithsulfuricacid(4.9).Collectthefiltrateandwashingsolutioninthesamebeaker.Reservethefilterpaperandacid-insolubleresiduefordeterminationofzincbyFAAS(asdescribedinannexC)fortheconcentratebeinganalysedandtheanalystperformingthetest,unlessithasbeenstatisticallyshown,byprevioustesting,thatthezinciscompletelysolubleintheinitialdecomposition.Ifthisstepisnotroutinelyperformed,regularchecksconfirmingthevalidityofitsexclusionshallbecarriedoutforeachconcentratetypebyeachanalyst.Similarly,alldocumentationcontainingresultswherethisstephasbeenexcludedshallcontainacommentindicatingthisfact.7.4Separationofaluminium,ironandmanganeseashydroxidesAdd15gofammoniumchloride(4.2)tothesolutionandswirlgentlytodissolve.NOTE1Iftheironcontentofthesampleisonlyafewpercent,theniron(III)solution(4.19)isaddedtothesolutiontoincreasethecontainedironinsolutiontoabout50mg.Heattonearboilingthenaddammonia(4.10)tothesolutionuntilcompleteprecipitationoccursandthen30mlinexcess.Add1gofammoniumpersulfate(4.11)tothesolution,heatuntilboilingandcontinueboilingfor1min.Standtoallowtheprecipitatetosettleout.Filterintoanother500mlbeakerthroughamedium-speedcellulosefilterpaperandwashtheprecipitateseveraltimeswithhotammoniawashingsolution(4.12).Collectthefiltrateandthewashingsolutionsinthesamebeaker.NOTE2Filtrationwillbeslowforhighleadcontentsamples.SIST ISO 13658:2001



ISO13658:2000(E)©ISO2000–Allrightsreserved5Washtheprecipitatebackintotheoriginalbeakerwithoutdamagingthefilterpaperanddissolveitwith10mlofhydrochloricacid(4.6).Add5gofammoniumchloride(4.2)tothesolution.Repeattheprecipitationbyadditionofammonia(4.10)andammoniumpersulfate(4.11).Boil,filterthroughtheoriginalfilterpaperandwashinthesamemannerasdescribedabove.Collectthefiltrateandwashingsolutioninthesamebeakerusedtocollectthefiltrateforthefirstseparationandplacethebeakeronahotplate(5.3).Heatgentlyandevaporatethesolutiontoabout200ml.Cooltoroomtemperature.Keepthehydroxideprecipitateforlatertreatment.7.5Titration7.5.1DeterminationofthetitrationfactoroftheEDTAsolutionNOTE1Inordertoobtainarelativeaccuracyofbetween0,1%and0,2%,itisnecessarytostandardizetheEDTAsolutionwithzincatthesametimeandunderthesameconditionsastheanalysis.Itisthusadvisableforthecalibrationtofollowthecompletesetofoperatingconditionssetdownfortheanalysis.Likewise,toimprovetherepeatabilityofthecalibration,itisusefultoprepareseveralzincreferencesolutions.TheEDTAsolutionshouldbestandardizedasfollows:Weighintothreeseparate500mlbeakersbetween0,055gand0,31gofhigh-purityzincmetal(4.1),tothenearest0,1mg,dependingonthezinccontentofthetestsample.Recordthesemassesasm1,m2andm3.Add10mlofhydrochloricacid(4.6)andwarmgentlytoaidthecompletedissolutionofthemetal.Add50mlofwaterand20gofammoniumchloride(4.2),swirlgentlytodissolveanddilutetoabout200mlwithwater.Add4dropsofbromothymolblueindicatorsolution(4.15)andneutralizebyaddingammonia(4.10)dropwiseuntiltheyellowcolourdisappears.Add7dropsofhydrochloricacid(4.5).NOTE2ApHmeter(5.4)maybeusedtoadjustthepHtoavalueof5,6insteadofusingthebromothymolblueindicator.Careshouldbetakentoensurethattheelectrodesarewashedoffwithwaterbeforecontinuingtheprocedure.Add20mlofhexamethylenetetraminebuffersolution(4.16)and20mlofmaskingsolution(4.17).Add10dropsofxylenolorangeindicator(4.18)tothesolution.SwirltodissolveandtitratewithEDTAstandardsolution(4.20)untilacolourchangetoyellowoccurs.RecordthevolumesasV1,V2andV3.Calculatetheintermediatefactors,fix,foreachbeakerusingthefollowingequation:fix=mx/Vxforx=1to3(1a)wherefixisthefactorobtainedfromthetitration;mxisthemassofzincweighed,ingrams;VxisthevolumeofEDTAsolution,inmillilitres.Iftherangeofvaluesforfi1,fi2andfi3exceeds0,00001g/ml,thenrepeatthestandardization.Otherwisecalculatethemeanfactorasfollows:f=(fi1+fi2+fi3)/3(1b)SIST ISO 13658:2001



ISO13658:2000(E)6©ISO2000–Allrightsreserved7.5.2TitrationofsamplesTothesamplepreparedin7.4,add4dropsofbromothymolblueindicatorsolution(4.15)andneutralizebyaddinghydrochloricacid(4.5)dropwiseuntilthebluecolourdisappears.Add7dropsinexcess.NOTE1ApHmeter(5.4)maybeusedtoadjustthepHtoavalueof5,6insteadofusingthebromothymolblueindicator.Careshouldbetakentoensurethattheelectrodesarewashedoffwithwaterbeforecontinuingtheprocedure.Add20mlofhexamethylenetetraminebuffersolution(4.16)and20mlofmaskingsolution(4.17).Add10dropsofxylenolorangeindicator(4.18)tothesolution.SwirltodissolveandtitratewithEDTAstandardsolution(4.20)untilacolourchangetoyellowoccurs.RecordthevolumeoftitrantusedasVt.NOTE2Ifthetestsamplecontainscadmium,itwillnotberemovedduringtheproceduregivenin7.5.Thecadmiumconcentrationisdeterminedseparatelyandacorrectionmadeforitspresence.ThemethodforthedeterminationofcadmiumisgiveninannexD.7.6Determinationofmassofzincintheacid-insolubleresidueandhydroxideprecipitateDeterminethemassofzinc(mZn)containedinboththeacid-insolubleresiduefromthedissolutionstep(7.3)andthehydroxideprecipitatefromtheseparationstep(7.4)asdescribedinannexC.7.7DeterminationofthecadmiumcontentofthesampleDeterminethecadmiumcontentCCdofthesampleasdescribedinannexD.8Expressionofresults8.1CalculationofthezinccontentofthetestportionsZntbZnCd%,VVfmmHC1001001000581(2)whereVtisthevolumeofEDTAusedtotitratethesamplealiquot,inmillilitres;VbisthevolumeofEDTAusedtotitratethereagentblank,inmillilitres;fisthezincequivalentfactoroftheEDTAsolution,ingramspermillilitre;mZnisthemassofzincintheresiduesasdeterminedinannexC,ingrams;misthetestportionmass,ingrams;Histhehygroscopicmoistureofthetestportion,expressedasapercentagebymass;CCdisthecadmiumconcentrationasdeterminedinannexD,expressedasapercentagebymass.NOTEInthecaseofapredriedtestportion,Hisequaltozero.SIST ISO 13658:2001



ISO13658:2000(E)©ISO2000–Allrightsreserved78.2CalculationofthezinccontentofthetestsampleProcesstheduplicatetestportionresultsforthetestsampleasperthechartinannexE.Ifnecessary,analyseextratestportionsasrequiredbyannexE.NOTEThereplicatelimitiscalculatedasfollows:Replicatelimit=2,8(2sr2)=0,16wheresristherepeatabilitystandarddeviation,inpercent(see10.1)9ApplicationtothetradingofzincconcentratesBetween-laboratoryprecisionisusedtodeterminetheagreementbetweentheresultsreportedbytwolaboratories.Theassumptionisthatbothlaboratoriesfollowedthesameprocedure.Calculatethefollowingquantities:CriticaldifferenceR=0,34RangeE=12where1isthefinalresult,inpercent,reportedbylaboratory1;2isthefinalresult,inpercent,reportedbylaboratory2.NOTEThecriticaldifferenceisoneofthefactorsusedtoderivethesplittinglimit.IfER,theresultsareinagreementandtheaverageofthetworesultscanbeusedforcommercialpurposes.10Accuracy10.1ExpressionofprecisionTheprecisionofthisanalyticalmethodisexpressedbythefollowingequations:NOTEAdditionalinformationisgiveninannexF.sr=0,041sR=0,12wheresristherepeatabilitystandarddeviation,inpercent;sRisthereproducibilitystandarddeviation,inpercent.SIST ISO 13658:2001



ISO13658:2000(E)8©ISO2000–Allrightsreserved10.2CheckoftruenessThetruenesso
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