1、Reference number ISO 13658:2000(E) ISO 2000 INTERNATIONAL STANDARD ISO 13658 First edition 2000-03-15 Zinc sulfide concentrates Determination of zinc content Hydroxide precipitation and EDTA titrimetric method Concentrs sulfurs de zinc Dosage du zinc Mthode par prcipitation dhydroxydes et titrage lE
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5、s given below. ISO 2000 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs m
6、ember body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 734 10 79 E-mail copyrightiso.ch Web www.iso.ch Printed in Switzerland ii ISO 2000 All rights reservedISO 13658:2000(E) ISO 2000 All rights reserved iii Contents Page
7、 Foreword.iv 1 Scope 1 2 Normative references 1 3 Principle2 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
8、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 spectroscopy12 Annex D (normative) Determination of cadmium by a
9、tomic 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 .19ISO 13658:2000(E) iv ISO 2000 All rights reserved Foreword ISO (the International Organization for St
10、andardization) 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 rig
11、ht 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
12、 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 bod
13、ies 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 Committe
14、e 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.INTERNATIONAL STANDARD ISO 13658:2000(E) ISO 2000 All rights reserved 1 Zinc sulfide concentrates Determination of zinc cont
15、ent 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 applicabil
16、ity 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)t o6 0%( m/m)zin c. 2 Normative references The following normat
17、ive 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 a
18、re 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
19、. 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, Labora
20、tory 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,
21、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 So
22、lvent extraction and EDTA titrimetric method. ISO/Guide 35:1989, Certification of reference materials General and statistical principles.ISO 13658:2000(E) 2 ISO 2000 All rights reserved 3P r i n c i p l e Dissolution of a test portion of zinc concentrate in bromine and nitric acid. Dissolution of an
23、y 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 comp
24、lexometric 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
25、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 a
26、nd dried in an oven at 50 C. 4.2 Ammonium chloride 4.3 Bromine 4.4 Nitric acid ( 20 1,42 g/ml) 4.5 Hydrochloric acid ( 20 1,16 g/ml to 1,19 g/ml) 4.6 Hydrochloric acid (1+1) Add 500 ml of hydrochloric acid (4.5) to 500 ml of water. 4.7 Sulfuric acid ( 20 1,84 g/ml) 4.8 Dilute sulfuric acid (1+1) Add
27、 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 ( 20 0,89 g/ml) 4.11 Ammonium persulfate 4.12 Ammonia washing solution Dissolve 20 g of ammonium chloride in 1 000 ml
28、of aqueous ammonia solution (1 + 100). 4.13 Ethanol, pure or denatured 4.14 Acetic acid ( 20 1,05 g/ml)ISO 13658:2000(E) ISO 2000 All rights reserved 3 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 Hexamethylenetetram
29、ine 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 indicat
30、or solution (1 g/l) D i ssolv e0 ,1go ft hesod iu msa l to fxy leno lo ra ng einw a te ran ddil u tet o1 00ml . 4.19 Iron(III) solution (1 0mgFe /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
31、 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.
32、4 pH meter 6S a m p l e 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
33、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 d
34、irectly from the laboratory sample.ISO 13658:2000(E) 4 ISO 2000 All rights reserved 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
35、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
36、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
37、 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
38、 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 carb
39、onaceous 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
40、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,
41、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, a
42、ll 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
43、 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)
44、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
45、the washing solutions in the same beaker. NOTE 2 Filtration will be slow for high lead content samples.ISO 13658:2000(E) ISO 2000 All rights reserved 5 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
46、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 colle
47、ct 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
48、 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 th
49、e 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 1 , m 2 and m 3 . Add 10 ml of hydrochloric acid (4.6) and warm gently to aid the complete dissolution of the metal. A
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