1、BRITISH STANDARD BS 6870-2.6: 1987 ISO 6994:1986 Analysis of aluminium ores Part 2: Chemical methods Section 2.6 Method for determination of aluminium content: EDTA titrimetric method ISO title: Aluminium ores Determination of aluminium content EDTA titrimetric method UDC 553.492:543BS6870-2.6:1987
2、This British Standard, having been prepared under the directionof the Non-ferrous Metals Standards Committee, waspublished under the authorityof the Board ofBSIandcomes into effect on 28 August1987 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference NFM/
3、31 Draft for comment85/36293 DC ISBN 0 580 16059 9 National foreword This Section ofBS6870 has been prepared under the direction of the Non-ferrous Metals Standards Committee. It is identical with ISO6994:1986 “Aluminium ores Determination of aluminium content EDTA titrimetric method”, published by
4、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 conventions are not identical with those used in British S
5、tandards; 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. Wherever the words “International Standard” appear, referring to this standard, they should be
6、 read as “Section ofBS6870”. Additional information. When adopting the text of the International Standard, it was noticed that in4.8 and4.16 hydrochloric acid with a density of1.17g/ml is specified, whereas in the UK hydrochloric acid with a density of1.18g/ml is normally used. This difference, whic
7、h will not affect the determination, has been brought to the attention of ISO in a proposal to amend the International Standard by specifying a wider range for the density of the hydrochloric acid required. A British Standard does not purport to include all the necessary provisions of a contract. Us
8、ers of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an inside back cover and a ba
9、ck 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. Cross-references International Standard Corresponding British Standard ISO 8557:1985 BS6870 Analysis of aluminium ores Sect
10、ion 2.2:1987 Method for determination of hygroscopic moisture in analytical samples gravimetric method (Identical) Amendments issued since publication Amd. No. Date of issue CommentsBS6870-2.6:1987 BSI 11-1999 i Contents Page National foreword Inside front cover 1 Scope and field of application 1 2
11、Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 3 6 Sampling and samples 3 7 Procedure 3 8 Expression of results 6 9 Test report 7 Table Precision data for aluminium determinations 7 Publication referred to Inside back coverii blankBS6870-2.6:1987 BSI 11-1999 1 1 Scope and field of application Th
12、is International Standard specifies an EDTA titrimetric method for the determination of the aluminium content of aluminium ores. The method is applicable to products having aluminium contents, expressed as aluminium oxide(Al 2 O 3 ), in the range30 to65% (m/m). 2 Reference ISO 8557, Aluminium ores D
13、etermination of hygroscopic moisture in analytical samples Gravimetric method. 3 Principle Decomposition of the test portion by either a) treatment with hydrochloric, nitric and sulfuric acids; NOTEThis method is recommended for ores containing gibbsite and/or boehmite and when the residue from the
14、dissolution of the test portion after silica volatilization is less than1% of the mass of the test portion. or b) sintering with sodium peroxide followed by brief fusion and dissolution of the melt with sulfuric acid; NOTEThis method is recommended for ores containing diaspore and when the residue f
15、rom the dissolution of the test portion after silica volatilization is greater than1% of the test portion. or c) fusion with sodium tetraborate/sodium carbonate flux followed by dissolution of the melt with sulfuric acid. NOTEThis method is suitable for all types of ore. Removal of silica by filtrat
16、ion to give a solution containing aluminium and other elements. Measurement of an aliquot portion and precipitation of aluminium and other elements except chromium, manganese and vanadium, by ammonium benzoate in acid solution. Filtration and dissolution of the precipitated benzoates in acid followe
17、d by precipitation of elements except aluminium by sodium hydroxide. Filtration of the precipitate followed by acid dissolution, reprecipitation with sodium hydroxide and filtration to recover coprecipitated aluminium. Addition of an excess of EDTA to the combined filtrates and determination of alum
18、inium content by back titration of the excess EDTA with zinc sulfate solution using xylenol orange as indicator. 4 Reagents During the analysis, use only reagents of analytical reagent grade and only distilled water or water of equivalent purity. 4.1 Sodium peroxide (Na 2 O 2 ), powdered. NOTESodium
19、 peroxide should be protected against humidity and should not be used once it has begun to agglomerate. 4.2 Sodium carbonate/sodium tetraborate flux Mix intimately3 parts by mass of anhydrous sodium carbonate (Na 2 CO 3 ) and1 part by mass of anhydrous sodium tetraborate (Na 2 B 4 O 7 ). 4.3 Ammoniu
20、m acetate,250g/l solution. Dissolve250g of ammonium acetate in900ml of water and adjust the pH to6 by the addition of glacial acetic acid(A 1,050g/ml). Dilute to1 litre. 4.4 Ammonium benzoate,100g/l solution. NOTETo obtain a clear solution after warming, it may be necessary to add up to5ml of ammoni
21、a solution(4.6). Filter if necessary to remove any particulate residue. 4.5 Hexamethylenetetramine (hexamine),250g/l solution. Dissolve25g of hexamethylenetetramine in70ml of water and dilute to100ml. 4.6 Ammonia solution, (A 0,9g/ml), diluted1+1. 4.7 Glacial acetic acid, (A 1,050g/ml). 4.8 Hydrochl
22、oric acid (A 1,17g/ml), diluted2+3.BS6870-2.6:1987 2 BSI 11-1999 4.9 Sodium hydroxide,160g/l solution. This solution shall be stored in a plastic bottle. 4.10 Sulfuric acid (A 1,84g/ml), diluted1+1. 4.11 Sulfuric acid (A 1,84g/ml), diluted1+3. 4.12 Sulfuric acid (A 1,84g/ml), diluted1+9. 4.13 Hydrof
23、luoric acid,40% (m/m), (A 1,13g/ml). 4.14 Sodium sulfate, (Na 2 SO 4 .10H 2 O),100g/l solution. 4.15 Potassium permanganate,1g/l solution. 4.16 Acid mixture Measure into a1litre beaker225ml of water and add cautiously, with stirring,175ml of sulfuric acid(A 1,84g/ml). Cool to room temperature and ad
24、d150ml of hydrochloric acid (A 1,17g/ml) and50ml of nitric acid (A 1,42g/ml). This solution shall be prepared for each series of determinations and any unused solution discarded. 4.17 Standard aluminium solution Dissolve approximately1,00g, weighed to the nearest0,0001g, of aluminium metal (not less
25、 than99.9%) in60ml of the hydrochloric acid(4.8), heating if necessary. Cool and dilute to the mark in a1000ml one-mark volumetric flask. Calculate the equivalent aluminium oxide concentration a of the standard solution, in grams per litre, using the equation where m 1 is the mass of aluminium metal
26、, in grams; P is the purity of aluminium used, in per cent. 4.18 Ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA), approximately0,05mol/l(18,6g/l) standard volumetric solution. 4.19 Zinc sulfate, standard volumetric solution,c(ZnSO 4 .7H 2 O)=0,05 mol/l. Dissolve14,5g of zinc sulfate h
27、eptahydrate (ZnSO 4 .7H 2 O) in water, transfer to a1000ml one-mark volumetric flask, dilute to volume andmix. 4.19.1 Standardization procedure 4.19.1.1 Titration of EDTA solution with standard zinc sulfate solution Using a pipette, add50ml of the EDTA solution(4.18) to a500ml beaker and add250ml of
28、 water. Add0,3ml of the methyl orange indicator(4.20) and, if necessary, add the ammonia solution(4.6) drop by drop until the colour just changes to yellow. Add20ml of the ammonium acetate solution(4.3) and adjust to pH5,7 0,1, using either the ammonia solution(4.6) or the glacial acetic acid(4.7).
29、Add0,5ml of the xylenol orange indicator(4.21) and titrate to the end-point (colour change yellow to purple) with zinc sulfate solution(4.19). Record the titre(V 1 ). 4.19.1.2 Determination of the equivalence factor for zinc sulfate solution Pipette50ml (V 3 ) of the standard aluminium solution(4.17
30、) into a500ml beaker, and add200ml of water. With a pipette, add50ml of the EDTA solution(4.18), and0,3ml of the methyl orange indicator(4.20). Add the ammonia solution(4.6) drop by drop until the colour just changes. Add20ml of the ammonium acetate solution(4.3) and a boiling aid. Boil for10min and
31、 cool. Adjust to pH5,7 0,1, as in4.19.1.1. Add0,5ml of the xylenol orange indicator(4.21) and titrate to the end-point with the zinc sulfate solution(4.19). Record the titre(V 2 ). Calculate the equivalence factor A of the zinc sulfate solution, using the formula where a is the mass, in grams, of al
32、uminium oxide per litre of standard aluminium solution(4.17). am 1 1,889 5 P 100 - = 1 ml zinc sulfate solution A () V 3 a V 1 V 2 - mg of Al 2 O 3 ”BS6870-2.6:1987 BSI 11-1999 3 4.20 Methyl orange indicator,0,1g/l solution. 4.21 Xylenol orange indicator,1g/l solution. Prepare each month and store i
33、n a dark bottle. 5 Apparatus Ordinary laboratory apparatus, and 5.1 Dishes, of inert material and sufficient size to take the required quantity of sample at a layer density of5mg/mm 2 . 5.2 Oven, electrically heated with a temperature-control device and mechanical convection, capable of maintaining
34、a temperature of105 5 C. NOTEThe oven should be checked by placing the usual number of drying dishes in position in the oven and then measuring the temperature in the vicinity of each dish to ensure that the required temperature is maintained throughout the oven, not just in the neighbourhood of the
35、 controlling element. 5.3 Platinum/gold(95/5) crucibles, of approximately25ml capacity for the fusion decomposition in7.6.1.3. 5.4 Zirconium crucibles, of approximately40ml capacity for the sinter decomposition in7.6.1.2. 5.5 Platinum crucibles 5.6 Filter papers 5.6.1 Medium-textured filter papers N
36、OTEWhatman540 grade have been found suitable. 5.6.2 Fast, hardened, ashless filter papers NOTEWhatman541 grade have been found suitable. 6 Sampling and samples 6.1 Sampling Laboratory samples shall be taken and ground to pass a1504m test sieve by the procedures specified in the relevant standards. 1
37、) 6.2 Preparation of the test sample Take approximately10g of the laboratory sample and place in the sample dish(5.1). Spread the sample evenly to give a layer density of approximately5mg/mm 2and allow the sample to equilibrate with the laboratory atmosphere for a minimum of2h. 7 Procedure 7.1 Numbe
38、r of determinations Carry out the analysis in duplicate and independently on one ore sample. NOTEThe expression “independently” implies a change of the person carrying out the analysis. If the same person must carry out the analysis, the procedure should be carried out at different times. 7.2 Test p
39、ortion Weigh, to the nearest0,0001g, approximately1g of air-equilibrated sample and record the mass (m). NOTEFor ores containing more than55% (m/m) of aluminium oxide, the mass of the test portion should be0,9g. 7.3 Determination of hygroscopic moisture content Simultaneously with the weighing of th
40、e test portion, weigh two test portions for the determination of hygroscopic moisture and carry out the determinations by the procedure specified inISO8557. 1) Where no International Standards exist, the relevant standards shall be the national standards. Two International Standards on this subject
41、are currently in preparation:ISO6137, Aluminium ores Method of sampling, andISO6140, Aluminium ores Preparation of samples.BS6870-2.6:1987 4 BSI 11-1999 7.4 Blank test In parallel with the decomposition of the test portion, prepare a blank test solution appropriate to the method of decomposition but
42、 with the omission of the test portion. When the analysis is carried out on several samples at the same time, the blank test value may be represented by one test, provided that the procedure is the same and the reagents used are from the same bottles. 7.5 Check test In each run, one analysis of a ce
43、rtified reference material of the same type of ore shall be carried out in parallel and under the same conditions with the analysis of one ore sample. NOTEThe certified reference material should be of the same type as the sample to be analysed. Such certified reference materials cannot, however, be
44、considered as being of the same type if the properties of the sample to be analysed differ from those of the certified reference material to such an extent that the analytical procedure must be changed substantially. 7.6 Preparation of the test solution 7.6.1 Decomposition of the test portion If the
45、 decomposition is to be based on acid attack, proceed as specified in7.6.1.1. If the decomposition is to be based on alkali sintering, proceed as specified in7.6.1.2. If the decomposition is to be based on fusion, proceed as specified in7.6.1.3. 7.6.1.1 Acid decomposition Transfer the test portion(7
46、.2) to a400ml beaker. Moisten with water and add60ml of acid mixture(4.16). Cover the beaker and heat at approximately80 C to decompose the sample (seenote 1). When the evolution of brown fumes ceases, carefully rinse the cover and wall of the beaker. Evaporate the uncovered solution to dense fumes
47、of sulfuric acid. Replace the cover and heat strongly for60min on a hotplate set to produce in the solution a temperature of210 10 C (seenote2). NOTE 1With samples of high iron content 15% (m/m) ofFe 2 O 3 , the initial heating should be conducted for an extended period. NOTE 2Determine the temperat
48、ure setting by using a separate test beaker containing a partial immersion thermometer in10mm depth of sulfuric acid (A 1,84g/ml). 7.6.1.2 Alkali sinter decomposition Transfer the test portion(7.2) to a dry zirconium crucible(5.4), add10g of the sodium peroxide(4.1) and mix intimately with a dry met
49、al spatula. Place in a muffle furnace at480 to500 C for45min. Remove the crucible and contents from the furnace and heat over a burner to melt the sinter (about30s). Continue heating the melt while swirling for a total time of2min. Allow the crucible to cool to room temperature (ametal block may be used to expedite this process). If necessary, clean the base of the crucible by wiping with, a damp filter paper. Place the crucible on its side in a400ml beaker, cover and add cautiously to the beaker140ml of the sul
