1、BRITISH STANDARD BS7020-7.1: 1988 ISO4689:1986 Analysis of iron ores Part 7: Methods for the determination of sulphur content Section 7.1 Gravimetric method ISO title: Iron ores Determination of sulfur content Bariumsulfate gravimetric method UDC622.341.1:620.113:622.7.016.34:622.7.092:543.845:543.2
2、1:620.1BS7020-7.1:1988 This British Standard, having been prepared under the directionof the Iron and Steel Standards Committee, was published under the authority ofthe Board of BSI andcomes intoeffect on 31 January1989 BSI 10-1999 The following BSI references relate to the work on this standard: Co
3、mmittee reference ISM/58 Draft for comment81/78396DC ISBN 0 580 16911 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Committee (ISM/-) to Technical Committee ISM/58, upon which the following bodies were repres
4、ented: British Steel Industry Institution of Mining and Metallurgy The following body was also represented in the drafting of the standard, through subcommittees and panels: British Ceramic Research Ltd. Amendments issued since publication Amd. No. Date of issue CommentsBS7020-7.1:1988 BSI 10-1999 i
5、 Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 References 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sampling and samples 2 7 Procedure 2 8 Expression of results 4 9 Test report 5 Annex A Flowsheet of the procedure for the accepta
6、nce of analytical values for test samples 6 Annex B Derivation of repeatability and permissible tolerance equations 7 Annex C Precision data obtained by international analytical trial 8 Figure Least-squares fit of precision against X for sulfur 8 Table Mass of test portion and volume of acid mixture
7、 (4.10) requiredfordecomposition 2 Publications referred to Inside back coverBS7020-7.1:1988 ii BSI 10-1999 National foreword This Section of BS7020 has been prepared under the direction of the Iron and Steel Standards Committee. It is identical with ISO4689-1986 “Iron ores Determination of sulfur c
8、ontent Barium sulfate gravimetric method” published by the International Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain con
9、ventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. In British Standards it is current prac
10、tice to use the spelling “sulphur” etc., instead of “sulfur”, etc. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Section of BS7020”. The reference to ISO5725 is for information only. Additional information. In clause 2 the footnote to ISO 308
11、2 no longer applies as this standard has now been published. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from
12、 legal obligations. Cross-references International Standard Corresponding British Standard BS5660 Methods of sampling iron ores ISO3081:1986 Part1:1987 Manual method of increment sampling (Identical) ISO3082:1987 Part2:1987 Mechanical method of increment sampling and sample preparation (Identical) I
13、SO3083:1986 BS5661:1987 Method for preparation of samples of iron ores by manual means (Identical) ISO7764:1985 BS7020 Analysis of iron ores Part1:1988 Method for the preparation of pre-dried test samples for chemical analysis (Identical) Summary of pages This document comprises a front cover, an in
14、side front cover, pagesi andii, pages 1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7020-7.1:1988 BSI 10-1999 1 1 Scope and field o
15、f application This International Standard specifies a barium sulfate gravimetric method for the determination of the sulfur content of iron ores. This method is applicable to a concentration range of0,01 to1,0% (m/m) of sulfur in natural iron ores, and iron ore concentrates and agglomerates includin
16、g sinter products. 2 References ISO3081, Iron ores Increment sampling Manual method. ISO3082, Iron ores Increment sampling and sample preparation Mechanical method 1) . ISO3083, Iron ores Preparation of samples Manual method. ISO7764, Iron ores Preparation of predried test samples for chemical analy
17、sis. 3 Principle Decomposition of a test portion by treatment with potassium chlorate and hydrochloric and nitric acids followed by evaporation to dryness. Dissolution of the salts in hydrochloric acid and filtration of the insoluble residue. Removal of the major portion of the iron in the filtrate
18、by extraction with methyl isobutyl ketone. Ignition of the insoluble residue and removal of silicon dioxide by evaporation with hydrofluoric and nitric acids. Fusion of the residue with sodium carbonate followed by leaching and filtration. Acidification of the filtrate and combination with the main
19、solution. Reduction of any remaining iron to the bivalent state, adjustment of the acidity and addition of barium chloride solution. Filtration of barium sulfate and gravimetric determination. 4 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled water
20、or water of equivalent purity. 4.1 Potassium chlorate (KClO 3 ), powder. 4.2 Sodium carbonate (Na 2 CO 3 ), anhydrous. 4.3 Zinc Use zinc with the lowest available sulfur content and with a particle size of1 to3mm. 4.4 Hydrochloric acid, 1,16 to1,19g/ml. 4.5 Hydrochloric acid, 1,16 to1,19g/ml, dilute
21、d2+1. 4.6 Hydrochloric acid, 1,16 to1,19g/ml, diluted1+1. 4.7 Hydrochloric acid, 1,16 to1,19g/ml, diluted2+100. 4.8 Nitric acid, 1,4g/ml. 4.9 Hydrofluoric acid, 40% (m/m), 1,13g/ml, or48% (m/m), 1,185g/ml. 4.10 Acid mixture: hydrochloric acid (4.4)+nitric acid (4.8),4+1. NOTEDo not store this mixtur
22、e; prepare immediately before use. 4.11 Barium chloride (BaCl 2 2H 2 O),100g/l solution. Dissolve100g of crystalline barium chloride dihydrate (BaCl 2 2H 2 O) in1litre of water, cover and heat to boiling point. Keep warm on a water bath for a minimum of2h and allow to cool to room temperature overni
23、ght. Store the solution in a plastics bottle and before each use, filter the required volume through a close-texture filter paper. 4.12 Hydrochloric acid wash solution, containing barium chloride. Filter10ml of barium chloride solution (4.11) through a close-texture filter paper, and dilute to1000ml
24、 with hydrochloric acid solution (4.7). 4.13 Sodium nitrate (NaNO 3 ), saturated solution. 4.14 Sodium carbonate (Na 2 CO 3 ),20g/l solution. Store in a plastics bottle. 4.15 Ammonium thiocyanate (NH 4 SCN),100g/l solution. 4.16 Silver nitrate, 20g/l solution. 4.17 Methyl orange, 0,1g/100ml solution
25、. Dissolve0,10g of methyl orange in100ml of water. 4.18 Methyl isobutyl ketone CH 3 COCH 2 CH(CH 3 ) 2 (4-Methylpentan-2-one). Pre-treat as follows before use: transfer200ml of methyl isobutyl ketone and100ml of hydrochloric acid solution (4.6) to a500ml separating funnel, and shake thoroughly for a
26、bout1min. Allow the layers to separate and discard the lower aqueous layer. 5 Apparatus Ordinary laboratory apparatus. 1) At present at the stage of draft.BS7020-7.1:1988 2 BSI 10-1999 6 Sampling and samples 6.1 Laboratory sample For analysis, use a laboratory sample of minus1004m particle size whic
27、h has been taken in accordance with ISO3081 or ISO3082 and prepared in accordance with ISO3082 or ISO3083. In the case of ores with significant contents of combined water or oxidizable compounds, use a particle size of minus1604m. NOTEA guideline on significant contents of combined water and oxidiza
28、ble compounds is incorporated in ISO7764. 6.2 Preparation of predried test samples Thoroughly mix the laboratory sample and, taking multiple increments, extract a test sample in such a manner that it is representative of the whole contents of the container. Dry the test sample at105 2 C as specified
29、 in ISO7764. (This is the predried test sample.) 7 Procedure 7.1 Number of determinations Carry out the analysis at least in duplicate in accordance with Annex A, independently, on one predried test sample. NOTEThe expression “independently” means that the second and any subsequent result is not aff
30、ected by the previous result(s). For this particular analytical method, this condition implies that the repetition of the procedure shall be carried out either by the same operator at a different time or by a different operator, including, in either case, appropriate recalibration. 7.2 Blank test an
31、d check test In each run, one blank test and one analysis of a certified reference material of the same type of ore shall be carried out in parallel with the analysis of the ore sample(s) under the same conditions. A predried test sample of the certified reference material shall be prepared as speci
32、fied in 6.2. NOTEThe certified reference material should be of the same type as the sample to be analysed and the properties of the two materials should be sufficiently similar to ensure that in either case no significant changes in the analytical procedure become necessary. When the analysis is car
33、ried out on several samples at the same time, the blank value may be represented by one test, provided that the procedure is the same and the reagents used are from the same reagent bottles. When the analysis is carried out on several samples of the same type of ore at the same time, the analytical
34、value of one certified reference material may be used. 7.3 Test portion Taking several increments, weigh, to the nearest0,000 2g, the amount of the predried test sample (6.2) specified in the table. NOTEThe test portion should be taken and weighed quickly in order to avoid reabsorption of moisture.
35、Table Mass of test portion and volume of acid mixture (4.10) required for decomposition 7.4 Determination 7.4.1 Decomposition of the test portion Place the test portion (7.3) in a500ml beaker, add1g of potassium chlorate (4.1) and3 to4ml of water, and mix thoroughly. Add, in accordance with the tabl
36、e, the required volume of acid mixture (4.10) and heat gently to decompose the test portion. Evaporate the solution to dryness on a hot-plate heated to about150 C, cool and add10ml of hydrochloric acid (4.4). Again evaporate to dryness, continuing the heating at about110 C for30min. Cool, add30ml of
37、 hydrochloric acid (4.6) and warm to dissolve soluble salts. NOTESamples that are not decomposed in1 to2h by this procedure should be digested by keeping the solution warm for an extended period. Add25ml of water and boil for about5min. Filter the solution through a close-texture paper, collecting t
38、he filtrate in a500ml beaker. Wash the paper and residue with the warm hydrochloric acid(4.7) until iron(III) ion can no longer be detected in the washings by testing a small portion with the ammonium thiocyanate solution (4.15). Reserve the filtrate and washings. Transfer the filter paper containin
39、g the residue to a platinum crucible. 7.4.2 Extraction of the bulk of the iron Evaporate the filtrate and washings (7.4.1) to about10ml. Cool and transfer the solution to a200ml separating funnel, using a total of50ml of hydrochloric acid (4.5), taken in several portions, to rinse the beaker. Add50m
40、l of the methyl isobutyl ketone (4.18) and shake thoroughly for about1min. Allow the layers to separate, then drain the lower aqueous layer into a second200ml separating funnel. Wash the organic layer by adding10ml of hydrochloric acid (4.5) and shaking for about30s. Allow the layers to separate, th
41、en combine the aqueous layer with the first. Repeat the washing of the organic phase with another10ml of hydrochloric acid (4.5), combine the aqueous solutions and reject the organic phase. Sulfur content, w S% (m/m) Mass of test portion g Volume of acid mixture ml 0,01w Su 0,1 0,1 w Su 0,5 0,5 w S
42、u 1,0 5,0 2,0 1,0 70 40 25BS7020-7.1:1988 BSI 10-1999 3 Add50ml of methyl isobutyl ketone (4.18) to the funnel containing the aqueous solution and shake thoroughly for about1min. Allow the layers to separate, then run the lower aqueous solution into a500ml beaker. Wash the organic phase by extractin
43、g twice with10ml of hydrochloric acid(4.5), transferring the washings to the beaker. Evaporate the combined aqueous solutions almost to dryness. Add10ml of acid mixture (4.10) to the salts and evaporate to dryness to decompose the organic matter. Add10ml of hydrochloric acid (4.4) and evaporate to d
44、ryness on a hot-plate heated to about150 C. Add a further10ml of hydrochloric acid (4.4) and evaporate to dryness, continuing the heating at110 C for about30min. Cool, add5ml of hydrochloric acid (4.4) and30ml of water to dissolve the salts, and reserve as the main solution. 7.4.3 Treatment of the r
45、esidue Moisten the filter paper containing the residue obtained in 7.4.1 with1 or2 drops of sodium nitrate solution (4.13), carefully heat the crucible to char the paper, then ignite at a temperature of800 to850 C. Allow the crucible to cool and moisten the ignited residue with a few drops of nitric
46、 acid (4.8). Add about5ml of hydrofluoric acid (4.9), and heat gently to dryness to remove silicon dioxide and nitric acid. NOTEWith high silicon contents, the treatment to remove silicon dioxide may be repeated with another5ml of hydrofluoric acid (4.9). Allow the crucible to cool, add3g of sodium
47、carbonate (4.2) and fuse the residue at about1000 C for15min. Place the cold crucible in a300ml beaker, add about100ml of warm water and heat to dissolve the melt. Remove the crucible and rinse with water. Filter the solution through a close-texture filter paper, collecting the filtrate in a300ml be
48、aker. Wash the filter paper several times with sodium carbonate solution (4.14), and discard the residue. Add0,5ml of methyl orange indicator solution(4.17) to the filtrate and washings and neutralize the solution by adding hydrochloric acid(4.6) in small portions, while stirring. Add5ml of hydrochl
49、oric acid (4.6) in excess and combine this solution with the main solution from 7.4.2. 7.4.4 Precipitation of barium sulfate Cover the beaker containing the combined solution with a watch glass, and heat to evaporate the solution to25ml. Allow to cool, add3ml of hydrochloric acid (4.6) and50ml of water, and heat to dissolve soluble salts. Heat on a water bath at60 to70 C and add1,0g of zinc (4.3) to reduce the remaining iron(III) to iron(II). Immediately after complete dissolution of the zinc, filter the solution thro
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