1、BRITISH STANDARD BS6870-3: 1989 Analysis of aluminium ores Part3: Method for multi-element analysis by wavelength dispersive X-ray fluorescenceBS6870-3:1989 This BritishStandard, having been prepared under the directionof the Non-ferrous Metals Standards Policy Committee, was published underthe auth
2、ority of the Board of BSI and comes into effect on 29 September1989 BSI12-1999 The following BSI references relate to the work on this standard: Committee reference NFM/31 Draft for comment87/40315DC ISBN 0 580 17094 2 Committees responsible for this BritishStandard The preparation of this BritishSt
3、andard was entrusted by the Non-ferrous Metals Standards Policy Committee to Technical Committee NFM/31, upon which the following bodies were represented: Aluminium Federation British Ceramic Research Ltd. British Geological Survey Department of Trade and Industry (Laboratory of the Government Chemi
4、st) Imperial College of Science and Technology Amendments issued since publication Amd. No. Date of issue CommentsBS6870-3:1989 BSI 12-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Preparation of the analysis sample 1 4 Reagents 1 5 Apparatus 2
5、6 Preparation of beads 3 7 Presentation of beads 5 8 XRF spectrometer 5 9 Ratio standard beads 6 10 Calibration standard beads 7 11 Alpha correction standard beads 8 12 Calibration 8 13 Line interference and background effects 9 14 Alpha corrections 10 15 Analysis 10 16 Correction for tungsten carbi
6、de contamination and loss on ignition 11 17 Reporting of results 11 18 Test report 11 Appendix A Tungsten carbide corrections with cobalt or nickel binder 13 Appendix B Monitoring of background and sensitivity 13 Appendix C Typical alpha corrections for rhodium end window X-ray tubes 14 Appendix D C
7、omputation of third order equations 14 Figure 1 Example of a fusion mould 12 Table 1 Ranges of content on the ignited basis 1 Table 2 Maximum allowable detection limits 6 Table 3 Composition of ratio standard beads 7 Table 4 Silicon dioxide/aluminium oxide binaries 8 Table 5 Minor constituents and s
8、ilicon dioxide 9 Table 6 Iron (III) oxide and minor constituents 9 Table 7 Rhodium end window tube empirical alpha corrections( 10 5 ) 14 Publications referred to Inside back coverBS6870-3:1989 ii BSI 12-1999 Foreword This Part of BS6870 has been prepared under the direction of the Non-ferrous Metal
9、s Standards Policy Committee. It is one of a series of Parts and Sections covering methods for the analysis of aluminium ores. General information, together with a list of contents, is given in Part1 and chemical methods of analysis are described in Part2. The method described in this Part of BS6870
10、 is based on the fused, cast bead technique. The flux used is of low melting point, which greatly assists mixing and dissolution. Binary standard beads are used for calibration and for line interference and background corrections, and binary or tertiary standard beads for inter-element (alpha) corre
11、ctions; this ensures that each of these parameters is determined separately. An ignited sample and an ignited-basis flux are used, so that dilution of sample in the melt is constant, hence simplifying calibration and analysis. A similar technique is described in BS1902-9.1, which uses many of the sa
12、me calibration standards. 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 page
13、s This document comprises a front cover, an inside front cover, pagesi andii, pages1 to16, 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.BS68
14、70-3:1989 BSI 12-1999 1 1 Scope This Part of BS6870 describes a method for the analysis of aluminium ores using wavelength dispersive X-ray fluorescence. It is applicable to materials containing not more than40% of iron(III) oxide (Fe 2 O 3 ) on the ignited basis. The ranges of content of constituen
15、ts covered by this standard are given in Table 1. Table 1 Ranges of content on the ignited basis NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Principle The powdered sample of aluminium ore is fused with a flux to destroy its mineralogical and
16、 particulate composition. The resultant melt is cast into a glass bead which is introduced into an X-ray fluorescence spectrometer. The intensities of the fluorescent X-rays of the required elements in the bead are measured and the chemical composition of the sample is determined by reference to cal
17、ibration graphs or equations. 3 Preparation of the analysis samples First check the sample with a magnet for adventitious iron, which may have been introduced during the crushing/grinding of the bulk sample. Then finely grind the sample (the bulk to be finer than1504m equivalent spherical diameter),
18、 using equipment made from a material which will not contaminate the sample, for example an agate pestle and mortar. When tungsten carbide equipment, for example a swing mill or percussion mortar, is used for the preparation of very hard aluminium ores, such as diaspore-types or those containing fre
19、e quartz, monitor any contamination and apply appropriate corrections to the analysis and loss on ignition figure (seeclause16). NOTEFurther corrections resulting from the binder in the tungsten carbide are shown in Appendix A. 4 Reagents 4.1 Flux. 1)The flux shall be a mixture of one part by mass l
20、ithium tetraborate (Li 2 B 4 O 7 ) to four parts by mass lithium metaborate (LiBO 2 ), the ratio being of the dry reagents. Both flux reagents shall be of an analytical quality. In practice the flux will contain moisture which shall be corrected for in one of the following two ways. a) Immediately b
21、efore it is to be used for the analysis, ignite the required quantity of flux overnight at700 C and then store in a desiccator. Oxide Range Silicon dioxide (SiO 2 ) Aluminium oxide (Al 2 O 3 ) Iron (III) oxide (Fe 2 O 3 ) Titanium oxide (TiO 2 ) Calcium oxide (CaO) Magnesium oxide (MgO) Phosphorus p
22、entoxide (P 2 O 5 ) Gallium oxide (Ga 2 O 3 ) % (m/m) 0.5 to30 20 to100 0.05 to40 0.05 to8 0.05 to2 0.05 to2 0.05 to5 0.005 to0.2 NOTEOther elements may be added as necessary, and in particular tungsten oxide (WO 3 )0.02% to5% (m/m) where a material containing tungsten carbide is used for sample pre
23、paration. 1) For information on the availability of suitable premixed fluxes, apply to the Enquiry Section, BSI, Linford Wood, Milton Keynes MK146LE, enclosing a stamped addressed envelope for reply.BS6870-3:1989 2 BSI 12-1999 b) Determine duplicate losses on ignition on1g portions of the well-mixed
24、 contents of each kilogram of flux used: this shall be either at700 C for1h or at1200 C for10min. Keep the flux tightly sealed except when in use. Determine the loss on ignition weekly, or for each kilogram of flux used, whichever is the more frequent. The loss on ignition is then used to calculate
25、the mass of the unignited flux m u(ing) needed to produce the required mass of flux on the ignited basis see equation(1). Recheck calibrations when batches of flux are changed. 4.2 Oxides or carbonates for glass beads. The reagents used to prepare the standard beads shall be pure oxides or carbonate
26、s of at least99.95% purity (excluding moisture or CO 2 ) for minor constituents and of at least99.99% purity for silicon dioxide, aluminium oxide and iron(III) oxide. The Ga 2 O 3content in all oxides and carbonates shall be less than0.001%(m/m). In order to obtain the reagents in a known stoichiome
27、try in terms of content they shall be treated before use as follows. a) Silicon dioxide, aluminium oxide and magnesium oxide. Immediately before use, determine the loss on ignition by igniting a known mass at1200 C for30min. Cool in a desiccator to room temperature, reweigh and calculate the loss in
28、 mass. After allowing for this loss, weigh the appropriate amount of the unignited material to prepare the standard bead. NOTE 1A granular form of silicon dioxide and aluminium oxide is preferable, since finely powdered or flaky forms have been shown to yield inconsistent loss on ignition results. I
29、t is advisable to use phosphorus pentoxide as desiccant for these reagents. b) Titanium oxide. Ignite at1000 C for30min before use. Cool in a desiccator to room temperature. c) Iron (III) oxide and lithium orthophosphate. Ignite at700 C for30min before use. Cool in a desiccator to room temperature.
30、d) Calcium carbonate, gallium oxide and tungsten oxide. Dry at220 C to constant mass before use. Cool in a desiccator to room temperature. NOTE 2A2h treatment is usually sufficient for drying. NOTE 3If very hard aluminium ores have been prepared using tungsten carbide equipment (seeclause3), tungste
31、n may have been introduced as a contaminant. Laboratories using tungsten carbide for sample grinding should therefore calibrate for WO 3in order to monitor its presence in samples. If necessary the analysis and the loss on ignition should be corrected for tungsten carbide contamination (seeclause16)
32、. 5 Apparatus 5.1 Fusion dishes, made from a platinum alloy that is not wetted by the melt. They shall be of sufficient capacity to hold the quantity of unfused flux and sample required by the size of the casting mould. NOTE 1An alloy consisting of95% platinum and5% gold is suitable. NOTE 2For a35mm
33、 diameter bead, where1.5g sample and7.5g flux are used, a fusion dish of50mL capacity is suitable. 5.2 Casting moulds, 2)made from a platinum alloy that is not wetted by the melt (seenote1 to5.1). The moulds shall be designed to give a circular bead of a diameter within the range25mm to40mm and of t
34、hickness to exceed the critical depth for the element lines used in analysis. The sides shall be set at a suitable angle to the vertical to ensure that the beads are readily released. If the top surface of the bead is to be used for analysis, there shall be a horizontal rim to the casting mould and
35、the mass of melt shall be sufficient to fill the mould and give a reproducible curved top surface. NOTECalibration and analysis should be carried out using the same pattern and size of casting mould throughout. If any changes in moulds are made, recalibration is required for top surfaces. For flat-b
36、ottomed surfaces recalibration is necessary if the change in diameter of the mould requires a different aperture of the spectrometer sample holder. (1) where m i is the required mass of the flux on the ignited basis (ing); L is the loss on ignition (in %). 2) For information on the availability of s
37、uitable casting and fusion moulds, apply to the Enquiry Section, BSI, Linford Wood, Milton Keynes MK146LE, enclosing a stamped addressed envelope for reply. m u 100m i 100L - =BS6870-3:1989 BSI 12-1999 3 5.3 Fusion moulds, 3)made from a platinum alloy that is not wetted by the melt (seenote1 to5.1).
38、 This is an optional alternative to5.1 and5.2, allowing both fusion and casting to be carried out in the same vessel (seeFigure 1). The volume of the dish shall be sufficient to hold the amount of unfused sample and flux required to fill the mould part of the vessel when fused. The mould part of the
39、 vessel shall comply with5.2. In particular, if the top surface of the bead is to be used for analysis, a horizontal rim shall be interposed between the top of the mould and the sides of the dish. NOTE 1If the rim is not present, concave top surfaces will be produced on the beads, which, if used, wo
40、uld not be conducive to accurate analysis. NOTE 2Once a size and type of mould has been selected it should be used throughout; if it is changed, recalibration is required. 5.4 Lids for dishes and fusion moulds, large enough to cover the vessels completely and made from an alloy of platinum, although
41、 not necessarily a non-wetted alloy. NOTEPlatinum itself is suitable. 5.5 Heat reservoir for casting mould (optional) NOTEA heat reservoir is usually required, especially when using moulds of small sizes, so that the mould does not cool too rapidly when removed from the furnace. A small piece of fla
42、t refractory material is suitable, e.g.a piece of sillimanite batt with approximate dimensions10mm thick by50mm square. 5.6 Air jet (optional) NOTEAn air jet helps to free the melt from the dish and cool the former rapidly. This can be any device whereby a narrow jet of air can be directed to the ce
43、ntre of the base of the casting dish. A convenient way to do this is to use the base of a Bunsen burner without a barrel. 6 Preparation of beads 6.1 Loss on ignition The mass of sample resulting after the loss on ignition determination shall be sufficient to produce an adequate mass of sample for th
44、e fusion procedure. In practice the mass required will be2g to3g weighed to 0.0005g. Dry the ground sample at110 5 C for at least4h or to constant mass. Store the samples in a desiccator containing phosphorus pentoxide while cooling. Weigh accurately2g to3g into a suitable fusion dish(5.1) or fusion
45、 mould(5.3) of known mass. Almost completely cover the vessel with a lid. Then either place the vessel in a muffle furnace and slowly increase the temperature to1 075 25 C, or start the ignition over a low flame, taking care to ensure oxidizing conditions, and slowly increase the temperature to a du
46、ll red heat over a period of20min, then transfer the vessel to a furnace at1 075 25 C. NOTE 1A tunnel kiln programmed to meet the above requirements may be used to carry out the slow increase in temperature and subsequent ignition. Ignite to constant mass at this temperature. NOTE 2Ignition for60min
47、 is usually sufficient. Remove the vessel from the furnace, completely cover with the lid, cool to room temperature in a desiccator and reweigh immediately. Correct the recorded loss on ignition figure for the effect of any tungsten carbide introduced into the sample being oxidized to WO 3(seeclause
48、16). 6.2 Fusion of samples and casting of beads NOTEAt several of the stages, a choice of procedures is given. Once a choice has been made, the procedure should be adhered to throughout, unless a recalibration is carried out. 6.2.1 General. Before fusing the samples and casting the beads, the follow
49、ing requirements shall be satisfied. a) Duplicate or single beads may be prepared; the method used shall be stated in the test report (seeclause18). NOTEDuplicate beads are preferable to single beads. 3) For information on the availability of suitable casting and fusion moulds, apply to the Enquiry Section, BSI, Linford Wood, Milton Keynes MK146LE, enclosing a stamped addressed envelope for reply.BS6870-3:1989 4 BSI 12-1999 b) The total mass of sample and flux shall be chosen for the particular casting mould type used
