1、TECHNICAL REPORT IS0 TR 11422 First edition 1996-02-I 5 Iron ores - Recommended procedures for iron ore dissolution using either acid digestion or alkali fusion Minerais de fer - Mbhodes recommandbes de dissolution des minerais de fer par digestion acide ou fusion alcaline Reference number - type 2,
2、 when the subject is still under technical development or where for any other reason there is the future but not immediate possibility of an agreement on an International Standard; - type 3, when a technical committee has collected data of a different kind from that which is normally published as an
3、 International Standard (“state of the art”, for example). Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be reviewed until the
4、data they provide are considered to be no longer valid or useful. ISOLIR 11422, which is a Technical Report of type 3, was prepared by Technical Committee ISOAC 102, Iron ores, Subcommittee SC 2, Chemical analysis. . . . 111 TECHNICAL REPORT 0 IS0 ISO/TR 11422:1996(E) Iron ores - Recommended procedu
5、res for iron ore dissolution using either acid digestion or alkali fusion 1 Background From time to time in ISQTC lOZ/SC 2, the view had been expressed that some degree of unification of procedures for the dissolution of iron ore test portions, based on selected established SC 2 procedures, would be
6、 of considerable benefit in the development of new analytical methods. This objective, coupled with the need to investigate possible procedure changes when increasing the mass of test portion in trace element methods, led to formation of the Dissolution Study Group in 1982. The activities of this St
7、udy Group and the details and results of an interlaboratory dissolution test were reported in document ISO/TC 102/SC 2 N772 E (annexes A and B to this report). Based on these results and consideration of certain dissolution procedures already in use in SC 2, several proposed dissolution procedures f
8、or various test portion masses were presented in document ISOEC 102/SC 2 N887 E, constituting a consolidated study group report for the period 1982 to 1986. Before these procedures could be finalized as acceptable models for use in future analytical methods, certain discrepancies of detail in the co
9、nduct of acid digestions had to be resolved. Accordingly, SC 2 members opinions were invited in the form of an explanatory note and questionnaire (documents ISO/TC 102/SC 2 N886 E and N888 E). A summary of the replies is appended (annex C), from which the conclusions to be drawn are as follows: a) I
10、n acid digestions, the beaker should be totally covered; in evaporations it should be partially covered. b) Temperatures (obtained in a test beaker) should be, for the initial digestion, 95C and, for subsequent digestion and evaporation, 105C. c) The evaporation to dehydrate silica should continue t
11、o dryness with 15 min further heating. d) The fused residue should be leached in the crucible, and not in the reserved main solution. 1 ISO/TR 11422:1996(E) Q IS0 These conclusions have been incorporated in the procedures presented in this report. It is not possible to recommend only one method for
12、acid digestion, because of the slightly different conditions required for varying test portion masses. Accordingly, methods are proposed for 2 g, 1 g and 0,5 g test portions, based on SC 2 methods applicable to or using such test portions. An important conclusion from the interlaboratory test was th
13、at not all of the parameters temperature, time of heating and target volume can be specified simultaneously. The test results showed that, if target volume needs to be specified, temperature and target volume take precedence, and heating time should be given only as a guide. 2 Sources of the recomme
14、nded procedures Acid digestion 4.1.1 2 g test portion : IS0 9685: 1991. I, 4.1.2 1 g test portion : IS0 9685: 1991, (1 4.1.3 0.5 g test portion : IS0 9682: 1991, Alkali fusion 4.2.1 IS0 9682: 1991, , 4.2.1 . IS0 4687: 1991, 11 4.2.2 . . IS0 9683: 1991. Alkali sinter fusion 4.3.1 IS0 7834: 1987, M 4.
15、3.2 . IS0 9683: 1991, NOTE 1 To take into account the survey responses and other considerations, the recommended procedures differ in minor detail from those in the above sources. 3 Assessment of acid digestion vs alkali fusion or sinter fusion Alkali fusion and sinter fusion processes have the dist
16、inct advantage of providing one-step dissolution which does not require time-consuming residue treatment; hence they are the first choice wherever possible. They have the major disadvantage, however, of adding very materially to the salt concentration of the solution, imposing difficulties with atom
17、ic absorption and ICP measurement techniques. To address this problem, the “8-4-5” low flux ratio procedure (4.2.1) has been devised to provide the lowest flux-to-sample ratio so far available in iron ore dissolution (2.4 flux to 1 test portion). Where the method can permit a separation of the fusio
18、n salts from the analyte, or where spectrophotometric techniques are involved and the salt concentration is accordingly less relevant, the flux ratio adopted in 4.3.1 (3 flux to 1 test portion) and in 4.2.2 (4 flux to 1 test portion) can then become acceptable. 0 IS0 ISO/TR 11422: 1996(E) Alkali fus
19、ion or sinter fusion is, in general, limited to test poRion masses not greater than 1 B* Where trace element determinations requiring 2 g test portions are involved, acid digestion tends to be preferred. However, it would not be impossible to devise an alkali sinter fusion method with a 2 g test por
20、tion and 6 g of sodium peroxide if separation of the analyte from the high concentration of salts could be contemplated. 4 Recommended procedures 4.1 Acid digestion procedure 4.1.1 2 g test portion A Reagents During the procedure, use only water of a grade that complies with IS0 3696:1987, Waferfor
21、analytical laboratory use-Specification and test methods. A.1 Sodium carbonate (Na,CO$ anhydrous. A.2 Sodium tetraborate (Na2B,0,). anhydrous. A.3 Hydrochloric acid, p I,16 g/ml to 1,19 g/ml. A.4 Hydrochloric acid, p 1.16 g/ml to 1.19 g/ml, diluted 1 + 1. A.5 Hydrochloric acid, p 1.16 g/ml to 1.19 g
22、/ml, diluted 2 + 100. A.6 Nitric acid, p 1.4 g/ml. A.7 Sulfuric acid, p 1.84 g/ml. A.8 Sulfuric acid, p 1,84 g/ml. diluted 1 + I. A.9 Hydrofluoric acid, p 1.13 g/ml, 40% (m/m), or p 1,19 g/ml, 48% (m/m). 3 ISOLIR 11422: 1996(E) B Apparatus Ordinary laboratory equipment, and B.l Glass beakers, 250 ml
23、 capacity. B.2 Platinum crucibles, minimum capacity 20 ml. B.3 Hotplate, calibrated using a partial-immersion thermometer, to produce in a 10 mm depth of sulfuric acid (A-7) in a 250 ml test beaker, temperatures of 95C and 105C. C Procedure Transfer a 2.0 g test portion to a 250 ml beaker (B.1) and
24、moisten with water. Add 50 ml of hydrochloric acid (A.3), cover with a watch glass and heat on a hotplate (B.3) for about 1 h at a temperature of 95C. NOTE 2 If after this digestion the amount of insoluble residue is high, raise the hotplate temperature to about 105C and continue heating, avoiding b
25、oiling. Add 5 ml of nitric acid (A.6) and 0.2 ml of sulfuric acid (A.8). and digest for 15 min at 105C. Displace the cover to provide a 6 mm gap and evaporate the solution at the 105*C hotplate setting to dryness. Continue heating for a further 15 min. NOTE 3 If the test sample contains significant
26、amounts of barium, omit the addition of sulfuric acid. Add 30 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and mix, then wash the watch glass and wall of the beaker and filter the solution through a close-texture filter paper containing filter pulp (0,3 g to 0.4 g
27、 dry mass) into a 200 ml beaker. Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened filter paper and transfer to the filter. Wash the paper with hydrochloric acid (A-5) until visibly free from iron, then finally wash with three or four portions of warm water
28、 Reserve the filtrate and washings as the main solution. Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a low temperature, then ignite at 75O*C to 8OOOC. Allow the crucible to cool. Add 0.3 ml of sulfuric acid (A.8) and 5 ml of hydrofluoric acid (A.9).
29、 evaporate slowly to remove silicon dioxide, then continue heating to remove the sulfuric acid. Ignite at 800C for several 4 0 IS0 ISO/TR 11422: 1996(E) minutes and cool. Add 0.8 g of sodium carbonate (A.l) and 0.4 g of sodium tetraborate (A.2) and mix. Heat at 1000C in a muffle furnace or over a pr
30、essurized air burner for a period sufficient to produce a clear melt, then allow the crucible to cool. Add 10 ml of hydrochloric acid (A-4) and heat to dissolve the melt and expel carbon dioxide. Cool, combine the solution with the evaporated and cooled main solution, transfer to a 100 ml volumetric
31、 flask, dilute to volume and mix. (This is the test solution.) 4.1.2 1 g test portion A Reagents During the analysis use only water of a grade that complies with IS0 3696:1987. A.1 Sodium carbonate (Na,CO,), anhydrous. A.2 Sodium tetraborate (N%B,O,), anhydrous. A.3 Hydrochloric acid, p 1.16 g/ml to
32、 1.19 g/ml. A.4 Hydrochloric acid, p 1.16 g/ml to I,19 g/ml, diluted 1 + 1. A.5 Hydrochloric acid, p 1.16 g/ml to 1,19 g/ml, diluted 2 + 100. A.6 Nitric acid, p 1.4 g/ml. A.7 Sulfuric acid, p 1,84 g/ml. A.8 Sulfuric acid, p 1,84 g/ml, diluted 1 + 1. A.9 Hydrofluoric acid, p 1,13 g/ml, 40% (m/m), or
33、p 1,19 g/ml, 48% (m/m). B Apparatus Ordinary laboratory equipment, and B-1 Glass beakers, 250 ml capacity. ISO/TR 11422: 1996(E) 8.2 Platinum crucibles, minimum capacity 20 ml. B.3 Hotplate, calibrated using a partial-immersion thermometer, to produce in a 10 mm depth of sulfuric acid (A.7) in a 250
34、 ml test beaker, temperatures of 95C and 105C. C Procedure Transfer a 1 ,O g test portion to a 250 ml tall-form beaker (B.1) and moisten with water. Add 25 ml of hydrochloric acid (A.3). cover with a watch glass and heat on a hotplate (B.3) for about 1 h at a temperature of 95*C. NOTE 4 If after thi
35、s digestion the amount of insoluble residue is high, raise the hotplate temperature to about 105C and continue heating, avoiding boiling. Add 2 ml of nitric acid (A.6) and 0.2 ml of sulfuric acid (A.8). and digest for 15 min at 105C. Displace the cover to provide a 6 mm gap and evaporate the solutio
36、n at the 105C hotplate setting to dryness. Continue heating for a further 15 min. NOTE 5 If the test sample contains significant amounts of barium, omit the addition of sulfuric acid. Add 20 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and mix. then wash the watch
37、 glass and wall of the beaker and filter the solution through a close-texture filter paper containing filter pulp (0.3 g to 0.4 g dry mass) into a 200 ml beaker. Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened filter paper and transfer to the filter. Wash
38、 the paper with hydrochloric acid (A-5) until visibly free from iron, then finally wash with three or four portions of warm water. Reserve the filtrate and washings as the main solution. Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a low temperature,
39、then ignite at 750C to 8OOOC. Allow the crucible to cool. Add 0,3 ml of sulfuric acid (A-8) and 5 ml of hydrofluoric acid (A.9). evaporate slowly to remove silicon dioxide, then continue heating to remove the sulfuric acid. Ignite at 8OO*C for several minutes and cool. Add 0.8 g of sodium carbonate
40、A.1) and 0.4 g of sodium tetraborate (A.2) and mix. Heat at 1000C in a muffle furnace or over a pressurized air burner for a period sufficient to produce a clear melt, then allow the crucible to cool. Q IS0 ISO/TR 11422:1996(E) Add 10 ml of hydrochloric acid (A-4) and heat to dissolve the melt and
41、expel carbon dioxide. Cool, combine the solution with the evaporated and cooled main solution, transfer to a 100 ml volumetric flask, dilute to volume and mix. (This is the test solution.) 4.1.3 0,s g test portion A Reagents During the analysis, use only water of a grade that complies with IS0 3696:
42、1987. A.1 Sodium carbonate (N%CO$, anhydrous. A.2 Sodium tetraborate (Na2B,0,), anhydrous. A.3 Hydrochloric acid, p 1,16 g/ml to 1,19 g/ml. A.4 Hydrochloric acid, p 1.16 g/ml to 1.19 g/ml, diluted 1 + 1. A.5 Hydrochloric acid, p I,16 g/ml to 1.19 g/ml, diluted 2 + 100. A.6 Nitric acid. p 1.4 g/ml. A
43、7 Sulfuric acid, p 1.84 g/ml. A.8 Sulfuric acid, p 1,84 g/ml, diluted 1 + 1. A.9 Hydrofluoric acid, p 1,13 g/ml, 40% (m/m), p 1.19 g/ml, 48% (m/m). B Apparatus Ordinary laboratory equipment, and B.l Glass beakers, 250 ml capacity. B.2 Platinum crucibles, minimum capacity 20 ml. ISO/TR 11422: 1996(E
44、) 0 IS0 B.3 Hotplate, calibrated using a partial-immersion thermometer, to produce in a 10 mm depth of sulfuric acid (A.7) in a 250 ml test beaker, temperatures of 95C and 105C. C Procedure Transfer a 0.5 g test portion to a 250 ml tall-form beaker (B.l) and moisten with water. Add 20 ml of hydrochl
45、oric acid (A.3). cover with a watch glass and heat on a hotplate (8.3) for about 1 h at a temperature of 95C. NOTE 6 If after this digestion the amount of insoluble residue is high, raise the hotplate temperature to about 105C and continue heating, avoiding boiling. Add 2 ml of nitric acid (A.6). 0.
46、2 ml of sulfuric acid (A.8) and digest for 15 min at 105C. Displace the cover to provide a 6 mm gap and evaporate the solution at the 105C hotplate setting to dryness. Continue heating for a further 15 min. NOTE 7 If the test sample contains significant amounts of barium, omit the addition of sulfur
47、ic acid. Add 20 ml of hydrochloric acid (A.4) and heat to dissolve the salts. Add 20 ml of water and mix, then wash the watch glass and wall of the beaker and filter the solution through a close-texture filter paper containing filter pulp (0,3 g to 0,4 g dry mass) into a 200 ml beaker. Carefully rem
48、ove all adhering particles with a rubber-tipped glass rod or piece of moistened filter paper and transfer to the filter. Wash the paper with hydrochloric acid (A.5) until visibly free from iron, then finally wash with three or four portions of warm water. Reserve the filtrate and washings as the mai
49、n solution. Transfer the filter paper and residue to a platinum crucible (B.2). Dry and char the paper at a low temperature, then ignite at 750C to 800C. Allow the crucible to cool. Add 0.3 ml of sulfuric acid (A.8) and 5 ml of hydrofluoric acid (A.9), evaporate slowly to remove silicon dioxide, then continue heating to remove the sulfuric acid. Ignite at 800C for several minutes and cool. Add 0.8 g of sodium carbonate (A.l) and 0.4 g of sodium tetraborate (A.2) and mix. Heat at lOOO*C in a muffle furnace or over a pressurized air burner for a period sufficient to
