1、BRITISH STANDARD BS 6870-2.8: 1987 ISO 8556:1986 Analysis of aluminium ores Part2: Chemical methods Section2.8 Method for determination of phosphorus content: spectrophotometric method ISO title: Aluminium ores Determination of phosphorus content Molybdenum blue spectrophotometric method UDC 553.492
2、:543BS6870-2.8:1987 This British Standard, having been prepared under the directionof the Non-ferrous Metals Standards Committee, waspublished under the authorityof the Board of BSI andcomes into effect on 28 August1987 BSI 01-2000 The following BSI references relate to the work on this standard: Co
3、mmittee reference NFM/31 Draft for comment84/42594 DC ISBN 0 580 16061 0 National foreword This Section ofBS6870 has been prepared under the direction of the Non-ferrous Metals Standards Committee. It is identical with ISO8556:1986 “Aluminium ores Determination of phosphorus content Molybdenum blue
4、spectrophotometric 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 conventions are n
5、ot 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. Wherever the words “International Standard” appear, r
6、eferring to this standard, they should be read as “Section ofBS6870”. Additional information. When adopting the text of the International Standard, it was noticed that in4.7 hydrochloric acid with a density of1.19g/ml and nitric acid with a density of1.41g/ml are specified, whereas in the UK acids w
7、ith densities of1.18g/ml and1.42g/ml respectively are normally used. These differences, which will not affect the determination, have been brought to the attention of ISO in a proposal to amend the International Standard by specifying wider ranges for the densities of the hydrochloric acid and nitri
8、c acid required. 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 legal obligations. Summary of pages This do
9、cument comprises a front cover, an inside front cover, pagesi andii, pages1 to6, 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. Cross-referen
10、ce International Standard Corresponding British Standard ISO 8558:1985 BS 6870 Analysis of aluminium ores Section2.1:1987 Method of preparation of pre-dried test samples (Identical) Amendments issued since publication Amd. No. Date of issue CommentsBS6870-2.8:1987 BSI 01-2000 i Contents Page Nationa
11、l foreword Inside front cover 1 Scope and field of application 1 2 Reference 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 Flowsheet of the procedure for the acceptance of test results 6 Table 1 Aliquot portions of t
12、est solution required 3 Table 2 Precision data for phosphorus determinations 5 Publication referred to Inside back coverii blankBS6870-2.8:1987 BSI 01-2000 1 1 Scope and field of application This International Standard specifies a molybdenum blue spectrophotometric method for the determination of ph
13、osphorus in aluminium ores and minerals. The method is applicable to materials having phosphorus contents, expressed as diphosphorus pentoxide between0,01 and5% (m/m). The arsenic content of the sample does not affect the determination. 2 Reference ISO 8558, Aluminium ores Preparation of predried te
14、st samples. 3 Principle Decomposition of a test portion, by either a) treatment with a mixture of hydrochloric acid, nitric acid and sulfuric acid; NOTEThis method is recommended for ores containing Gibbsite and/or Boehmite and when the residue from the dissolution of the test portion after silica v
15、olatilization is less than1% of the test portion. or b) sintering with sodium peroxide followed by a brief fusion. Dissolution of the melt with sulfuric acid. NOTEThis method is recommended for ores containing Diaspore and when the residue from the dissolution of the test portion is greater than1% o
16、f the mass of the test portion. Dehydration of silica, dissolution of salts, filtration and ignition of the impure silica. Removal of the silica by evaporation with hydrofluoric and sulfuric acids. Fusion with sodium carbonate and sodium tetraborate, dissolution with hydrochloric acid and combinatio
17、n with the main solution. Addition of molybdate to convert the phosphate to molybdophosphate complex, and reduction to molybdenum blue with ascorbic acid. Spectrophotometric measurement of the absorbance of the molybdenum blue complex at approximately710nm. 4 Reagents During the analysis, use only r
18、eagents of recognized analytical reagent grade, and only distilled water or water of equivalent purity. 4.1 Sodium peroxide (Na 2 O 2 ), powder. NOTESodium peroxide should be protected against humidity and should not be used once it has begun to agglomerate. 4.2 Sodium carbonate/sodium tetraborate f
19、lux. Mix intimately3 parts by mass of anhydrous sodium carbonate (Na 2 CO 3 ) with1 part by mass of anhydrous sodium tetraborate (Na 2 B 4 O 7 ). 4.3 Sulfuric acid, 20 1,84g/ml, diluted1+1. 4.4 Sulfuric acid, 20 1,84g/ml, diluted1+9. 4.5 Hydrofluoric acid,40% (m/m) ( 20 1,13g/ml) or48% (m/m) ( 20 1,
20、18g/ml). 4.6 Hydrobromic acid,40% (m/m) ( 20 1,38g/ml) or47% (m/m) ( 20 1,48g/ml). 4.7 Acid mixture Measure into a1 litre beaker225ml water and add cautiously, with mixing,175ml of sulfuric acid(4.3). Cool well and add150ml hydrochloric acid ( 20 1,19g/ml) and50ml of nitric acid ( 20 1,41g/ml). Prep
21、are this solution fresh for each series of tests, and discard any unused solution, flushing copiously with water. 4.8 Ascorbic acid (C 6 H 8 O 6 ),2g/l solution. Prepare this solution fresh on the day of use. 4.9 Disodium disulfite (Na 2 S 2 O 5 ),150g/l solution. Prepare this solution fresh on the
22、day of use. 4.10 Sodium molybdate (Na 2 MoO 4 .2H 2 O),50g/l solution. 4.11 Bismuth, solution. Dissolve4,25g of bismuth sulfate Bi 2 (SO 4 ) 3 (specification90%) or2,80g of bismuth oxycarbonate(90% Bi 2 O 3 ) in280ml of sulfuric acid(4.3) and heat until the salt is dissolved completely. Cool to room
23、 temperature, transfer to a1000ml one-mark volumetric flask, dilute to the mark with water and mix. 1ml of this solution contains2,5mg of Bi 2 O 3 . 4.12 Phosphorus, standard solution corresponding to0,02g ofP 2 O 5per litre. Dry several hundred milligrams of potassium dihydrogen orthophosphate (KH
24、2 PO 4 ) at105 C to constant mass and allow to cool in a desiccator. Dissolve0,192g of dried salt in water, transfer to a500ml one-mark volumetric flask, dilute to the mark with water and mix. Transfer25,0ml of this solution to a250ml one-mark volumetric flask, dilute to the mark with water and mix.
25、 1ml of this standard solution contains0,02mg of P 2 O 5 . 5 Apparatus Ordinary laboratory apparatus and 5.1 Dishes, of inert material of sufficient size to take the required quantity of sample at a layer density of5mg/mm 2 .BS6870-2.8:1987 2 BSI 01-2000 5.2 Oven, electrically heated, with a tempera
26、ture-control device capable of maintaining 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
27、 oven, not just in the neighbourhood of the controlling element. 5.3 Muffle furnace, adjustable from480 C to greater than1000 C. 5.4 Zirconium crucibles, approximately40ml capacity, for sinter decomposition. 5.5 Platinum crucibles, for treatment of the residue in7.5.3. 5.6 Desiccator, containing eit
28、her fresh magnesium perchlorate or activated alumina as desiccant. NOTE 1Activated alumina should be activated by heating at300 10 C overnight. NOTE 2When discarding magnesium perchlorate, flush down the sink using copious quantities of water. 5.7 Spectrophotometer, suitable for measurement of absor
29、bance in the region of710nm. 6 Sampling and samples 6.1 Samples Laboratory samples shall be taken and ground to pass a1504m test sieve in accordance with the methods specified in the relevant standards. 1) 6.2 Preparation of the test sample Prepare the test sample by drying it in an oven, following
30、the procedure specified inISO8558. 7 Procedure 7.1 Number of determinations Carry out the analysis in duplicate and independently on one ore sample. NOTEThe expression “independently” implies the change of the person carrying out the analysis. If the same person must carry out the analysis, the proc
31、edure should be carried out at a different time. 7.2 Test portion Weigh, to the nearest0,001g, approximately1g of the test sample obtained in accordance withclause6. 7.3 Blank test In parallel with the decomposition of the test portion, prepare a blank solution according to the method of decompositi
32、on, but with the omission of the test portion. 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 the reagents used are from the same bottles. 7.4 Check test In each run, one analysis of a c
33、ertified 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 material cannot, however, b
34、e 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. 7.5 Determination 7.5.1 Decomposition of the test portion If the decomposition is
35、 to be based on acid attack, proceed as specified in7.5.1.1. If the decomposition is to be based on alkali sintering, proceed as specified in7.5.1.2. 7.5.1.1 Acid attack Transfer the test portion(7.2) to a400ml beaker. Moisten with water and add as a freshly prepared mixture,60ml of the acid mixture
36、(4.7). Cover the beaker and heat at approximately80 C to decompose the sample (seenote1). When the evolution of brown fumes ceases, carefully rinse the cover and wall of the beaker. Evaporate the uncovered solution to dense fumes of sulfuric acid. Replace the cover and heat strongly for60min on a ho
37、tplate set to produce in the solution a temperature of210 10 C (seenote2). NOTE 1With samples of high iron content 15% (m/m) Fe 2 O 3 , the initial heating should be conducted for an extended period. NOTE 2Determine the temperature setting using a separate test beaker containing a partial immersion
38、thermometer in a10mm depth of sulfuric acid ( 20 1,84g/ml). 1) Where no International Standards exist, the relevant standards shall be the national standards. Two International Standards on this subject are currently in preparation: ISO6137, Aluminium ores Method of sampling, andISO6140, Aluminium o
39、res Preparation of samples.BS6870-2.8:1987 BSI 01-2000 3 7.5.1.2 Alkali sinter attack CAUTION Protective goggles must be used during the following attack. 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 metal spatula.
40、Place in the muffle furnace(5.3), controlled 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 molten state, with swirling, for a total time of2min. Allow the crucible to cool (a metal block can be us
41、ed to expedite this process). If necessary, clean the base of the crucible by wiping with a damp filter paper. Then, place it, lying on its side, in a400ml beaker, cover, and add cautiously to the beaker140ml of the sulfuric acid(4.4). Add20ml of the sulfuric acid(4.3) and digest to leach the conten
42、ts of the crucible. Remove the crucible when the contents are completely leached and rinse well into the solution in the beaker. Carefully rinse the cover and wall of the beaker. Evaporate the uncovered solution to dense fumes of sulfuric acid. Replace the cover and heat strongly for60min on a hotpl
43、ate set to produce in the solution a temperature of210 10 C. NOTEDetermine the temperature setting using a separate test beaker containing a partial immersion thermometer in a10mm depth of sulfuric acid ( 20 1,84g/ml). 7.5.2 Dissolution and filtration Cool the solution from7.5.1.1 or7.5.1.2 to room
44、temperature, cautiously add130ml of water and heat at80 to90 C for at least40min with stirring to completely dissolve the salts. Filter while hot through a medium-texture filter paper, collecting the filtrate in a250ml one-mark volumetric flask. Rinse the beaker with water and, using a rubber tipped
45、 glass rod, clean the beaker and transfer the residue quantitatively to the paper. Wash the paper and residue five times with5 to10ml portions of hot water. Reserve the filtrate and washing. Retain the filter paper and residue and continue according to7.5.3. 7.5.3 Treatment of the residue Transfer t
46、he filter paper and residue from7.5.2 to a pre-ignited, tared platinum crucible(5.5). Dry and char slowly and then ash the filter paper by increasing the temperature to600 to700 C in the muffle furnace. Allow the crucible to cool and moisten the residue with a few drops of water. Add5drops of the su
47、lfuric acid(4.3) and, depending on the silica content,5 to15ml of the hydrofluoric acid(4.5). Evaporate carefully in a fume cupboard to dryness to expel silica and sulfuric acid. Allow the crucible to cool in the desiccator(5.6) and weigh it. Determine the mass of the residue to ensure that the requ
48、irements of theclause3 are met. Add0,7 0,1g of the flux(4.2). Fuse at above1000 C for4 to5 min in the muffle furnace, swirl the melt briefly then return to the furnace for1 to2min. Allow the crucible to cool, add10ml of the sulfuric acid(4.4) and warm to dissolve the fused mass. Transfer the solutio
49、n to the reserved filtrate(7.5.2), rinsing the crucible with water. Cool to room temperature, dilute to the mark with water and mix. This is the test solution. 7.5.4 Treatment of the test solution For P 2 O 5contents in the range0,01 to1% (m/m), pipette aliquot portions directly from the test solution. For P 2 O 5contents in the range1 to5% (m/m), pipette10ml of the test solution into a100ml one-mark volumetric flask, dilute to volume with water and mix. This is the diluted test solution. Transfer to a150ml beaker the aliquo
