1、BRITISH STANDARD BS7020-6.2: 1993 ISO4687-1: 1992 Analysis of iron ores Part 6: Methods for the determination of phosphorus content Section 6.2 Molybdenum blue spectrophotometric method UDC 553.31:543.42:546.18BS7020-6.2:1993 This British Standard, having been prepared under the directionof the Iron
2、 and Steel Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 15 October1993 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference ISM/58 Draft for comment90/46640DC ISBN 0 580 22293 4 Committees resp
3、onsible for this British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) to Technical Committee ISM/58, upon which the following bodies were represented: British Steel Industry Institution of Mining and Metallurgy Coopted membe
4、rs 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 CommentsBS7020-6.2:1993 BSI 07-1999 i Contents Page Committees responsible Inside front cover National forewor
5、d ii 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Sampling and samples 2 7 Procedure 2 8 Expression of results 4 9 Test report 5 Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test samples 6 Annex B (informative) Derivation
6、 of repeatability and permissible tolerance equations 7 Annex C (informative) Precision data obtained by international analytical trials 7 Figure C.1 Least-squares fit of precision against X for phosphorus 7 Table 1 Preparation of6mol/l hydrochloric acid 1 Table 2 Aliquots of test solution or dilute
7、d test solution 3 Table B.1 Phosphorus contents of test samples for interlaboratory tests 7 List of references Inside back coverBS7020-6.2:1993 ii BSI 07-1999 National foreword This Section of BS7020 has been prepared under the direction of the Iron and Steel Standards Policy Committee and is identi
8、cal with ISO4687-1:1992 Iron ores Determination of phosphorus content Part1: Molybdenum blue spectrophotometric method published by the International Organization for Standardization (ISO). The Technical Committee has reviewed the provisions of ISO648, to which normative reference is made in the tex
9、t, and has decided that they are acceptable for use in conjunction with this standard. A related British Standard to ISO648:1977 is BS1583:1986 Specification for one-mark pipettes. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards a
10、re responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International standard Corresponding British Standard ISO1042:1983 BS1792:1982 Specification for one-mark volumetric flasks (Identical) BS5660
11、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) ISO3083:1986 BS5661:1987 Method for preparation of samples of iron ores by manual means (Identical)
12、 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 inside front cover, pagesi andii, pages1 to8, an inside back cover and a back cover. This standard h
13、as been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7020-6.2:1993 BSI 07-1999 1 1 Scope This part of ISO4687 specifies a molybdenum blue spectrophotometric method for the determination of the phospho
14、rus content of iron ores. This method is applicable to phosphorus contents between0,003%(m/m) and2%(m/m) in natural iron ores, iron ore concentrates and agglomerates, including sinter products. The presence of arsenic, barium or titanium does not affect the result. 2 Normative references The followi
15、ng standards contain provisions which, through reference in this text, constitute provisions of this part of ISO4687. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO4687 are encouraged to invest
16、igate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO648:1977, Laboratory glassware One-mark pipettes. ISO1042:1983, Laboratory glassware One-mark volumetric flasks. ISO30
17、81:1986, Iron ores Increment sampling Manual method. ISO3082:1987, Iron ores Increment sampling and sample preparation Mechanical method. ISO3083:1986, Iron ores Preparation of samples Manual method. ISO7764:1985, Iron ores Preparation of predried test samples for chemical analysis. 3 Principle Fusi
18、on of the test portion in sodium carbonate and sodium tetraborate flux and dissolution of the cooled melt in hydrochloric acid. Treatment of an aliquot with sodium sulfite and perchloric acid followed by treatment of the phosphorus with molybdate and hydrazine sulfate to form a molybdenum blue compl
19、ex. Spectrophotometric measurement of the molybdenum blue complex at an absorption peak wavelength of approximately820nm. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Sodium carbonate (Na 2 CO 3 ), anhydr
20、ous. 4.2 Sodium tetraborate (Na 2 B 4 O 7 ), anhydrous. 4.3 Hydrochloric acid, 1,16g/ml to1,19g/ml. 4.4 Hydrochloric acid, c(HCl)=6mol/l. Determine, at ambient temperature, the density of the hydrochloric acid(4.3) and, in accordance with Table 1, measure the appropriate volume into a1000ml one-mark
21、 volumetric flask. Dilute to volume with water, mix and cool. Readjust the volume and re-mix. Table 1 Preparation of6mol/l hydrochloricacid 4.5 Perchloric acid, 1,54g/ml,60%(m/m) solution or 1,70g/ml,72%(m/m) solution. 4.6 Perchloric acid, c(HClO 4 )=3mol/l. Transfer250ml of water to a1000ml one-mar
22、k volumetric flask and add250ml of72%(m/m) perchloric acid(4.5) or325ml of60%(m/m) perchloric acid(4.5), mix and cool. Dilute to volume with water and mix. 4.7 Sodium sulfite (Na 2 SO 3 ), solution,100g/l. This solution should be prepared freshly on the day of use in a sufficient quantity for the nu
23、mber of tests being made. 4.8 Hydrazine sulfate (NH 2 .NH 2 .H 2 SO 4 ), solution2g/l. This solution should be prepared freshly on the day of use in a sufficient quantity for the number of tests being made. 4.9 Matrix solution. Transfer1,6g of sodium carbonate(4.1) and0,8g of sodium tetraborate(4.2)
24、 to a250ml beaker and add40ml of water. While stirring, add cautiously70ml of hydrochloric acid(4.4). Heat to boiling, boil for1min, cool and transfer to a200ml one-mark volumetric flask. Dilute to volume with water and mix. 4.10 Ammonium heptamolybdate (NH 4 ) 6 Mo 7 O 24 .4H 2 O), solution,20g/l.
25、Dissolve20g of ammonium heptamolybdate in500ml of water. When dissolved, add slowly, with mixing,250ml of72%(m/m) perchloric acid(4.5) or325ml of60%(m/m) perchloric acid(4.5), and cool. Transfer to a1000ml one-mark volumetric flask and dilute to volume with water. Density g/ml Hydrochloric acid(4.3)
26、 required ml 1,16 1,17 1,18 1,19 575 535 500 470BS7020-6.2:1993 2 BSI 07-1999 4.11 Phosphorus, standard solution,204g/ml. Dry potassium dihydrogen orthophosphate (KH 2 PO 4 ) at110 C to constant mass and cool in a desiccator. Dissolve0,2197g of the dried salt in water, transfer to a250ml one-mark vo
27、lumetric flask, dilute to volume with water and mix. Transfer25,0ml of this solution to a250ml one-mark volumetric flask, dilute to volume with water and mix. 5 Apparatus Ordinary laboratory apparatus, including one-mark pipettes and one-mark volumetric flasks complying with the specifications of IS
28、O648 and ISO1042 respectively, and 5.1 Platinum or suitable platinum alloy crucibles, of capacity not less than25ml. 5.2 Muffle furnace, to provide a temperature of1020 C. 5.3 Combined magnetic stirrer/hotplate 5.4 Stirring bars, polytetrafluoroethylene-coated,10mm long. 5.5 Water bath, at boiling t
29、emperature. 5.6 Spectrophotometer, suitable for measurement of absorbance at approximately820nm. 6 Sampling and samples 6.1 Laboratory sample For analysis, use a laboratory sample of minus104m particle size which has been taken in accordance with ISO3081 or ISO3082 and prepared in accordance with IS
30、O3082 or ISO3083. In the case of ores with significant contents of combined water or oxidizable compounds, use a particle size of minus1604m. NOTE 1A guideline on significant contents of combined water and oxidizable compounds is incorporated in ISO7764. 6.2 Preparation of predried test samples Thor
31、oughly mix the laboratory sample and, taking multiple increments, extract a test sample in such manner that it is representative of the whole contents of the container. Dry the test sample at105 C 2 C as specified in ISO7764. (This is the predried test sample.) 7 Procedure 7.1 Number of determinatio
32、ns Carry out the analysis at least in duplicate in accordance with Annex A, independently, on one predried test sample. NOTE 2The expression “independently” means that the second and any subsequent result is not affected by the previous result(s). For this particular analytical method, this conditio
33、n 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 Test portion Taking several increments, weigh, to the nearest0,0002g, approximately0,5g of the pred
34、ried test sample obtained in accordance with6.2. NOTE 3The test portion should be taken and weighed quickly to avoid reabsorption of moisture. 7.3 Blank test and 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
35、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 specified in6.2. NOTE 4The certified reference material should be of the same type as the sample to be analysed and the properties of the two mat
36、erials should be sufficiently similar to ensure that in either case no significant changes in the analytical procedure become necessary. When the analysis is carried 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 t
37、he 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 value of one certified reference material may be used. 7.4 Determination 7.4.1 Decomposition of the test portion Add0,80g of sodium carbona
38、te(4.1) to a platinum or platinum alloy crucible(5.1). Transfer the weighed test portion(7.2) to the crucible and mix well using a platinum or stainless-steel rod. Add0,4g of sodium tetraborate(4.2) and again mix well, using the metal rod. Place the crucible in a muffle furnace(5.2) set at1020 C, fo
39、r30 min. Remove the crucible from the furnace and gently swirl the melt as it solidifies. Allow to cool. 7.4.2 Preparation of the test solution Place the polytetrafluoroethylene-coated stirring bar(5.4) in the cooled crucible and place the crucible on its side in a150ml low-form beaker. Add25ml of w
40、ater and35ml of hydrochloric acid(4.4), cover with a watch-glass, place on the magnetic stirrer/hotplate(5.3) and heat with stirring until dissolution of the melt is complete. NOTE 5The crucible may need to be rotated to ensure that the solution reaches the whole of the melt.BS7020-6.2:1993 BSI 07-1
41、999 3 Cool the solution, remove and rinse the crucible and transfer the solution to a100ml one-mark volumetric flask. Dilute to volume with water and mix. (This is the test solution.) 7.4.3 Treatment of the test solution With test samples containing less than0,2%(m/m) phosphorus, proceed as specifie
42、d in7.4.3.1. With test samples containing more than0,2%(m/m) phosphorus, proceed as specified in7.4.3.2. 7.4.3.1 Phosphorus content below0,2%(m/m) Into two250ml tall-form beakers, measure respectively an aliquot of test solution(7.4.2) and an aliquot of blank test solution in accordance with Table 2
43、. Add to each the specified volume of matrix solution(4.9) (seeTable 2). Prepare an iron compensation solution by measuring into a250ml tall-form beaker a corresponding aliquot of test solution(7.4.2) and adding the specified volume of matrix solution(4.9) (seeTable 2). 7.4.3.2 Phosphorus content ab
44、ove0,2%(m/m) Prepare a diluted test solution and a diluted blank test solution as follows: into two100ml one-mark volumetric flasks, measure10,0ml aliquots of test solution(7.4.2) and blank test solution respectively. Dilute to volume with matrix solution(4.9) and mix. Into two250ml tall-form beaker
45、s, measure respectively an aliquot of diluted test solution and an aliquot of diluted blank test solution in accordance with Table 2. Add to each the specified volume of matrix solution(4.9) (seeTable 2). Table 2 Aliquots of test solution or dilutedtest solution 7.4.4 Spectrophotometric measurement
46、Add15ml of sodium sulfite solution(4.7) to the solutions obtained in either7.4.3.1 or7.4.3.2. Mix, cover and allow to stand at room temperature for2min. Transfer to a water bath at boiling temperature(5.5) immersing the beakers to the solution level, heat for10 min and remove the beakers from the ba
47、th. Add stirring rods and, mixing after each addition, add, except to the iron compensation solution25ml of perchloric acid(4.6),20ml of water and10,0ml of ammonium heptamolybdate solution(4.10) (seenotes6 and7). NOTE 6With the iron compensation solution, increase the volume of perchloric acid(4.6)
48、from25ml to35ml, add20ml of water, but omit the addition of ammonium heptamolybdate solution(4.10). NOTE 7For convenience, a premixed stock of perchloric acid(4.6) and water in the ratio of25ml to20ml may be prepared in sufficient quantity for the required number of tests in the series. To provide f
49、or the seven tests required in a normal test and calibration series, add200ml of perchloric acid(4.6) to160ml of water and mix thoroughly. Use45ml of this diluted perchloric acid-water mixture in place of the specified separate additions of perchloric acid(4.6) and water. Add2,0ml of hydrazine sulfate solution(4.8), mix and transfer to a water bath at boiling temperature(5.5), immersing the beaker to the solution level, and heat at the maximum temperature of the bath for20min. Cool in a water bath, transfer to a100ml one-mark vol
