ISO 6994-1986 Aluminium ores Determination of aluminium content EDTA titrimetric method《铝土矿石 铝含量的测定 EDTA滴定法》.pdf

1、International Standard 6994 0 Q NOTE - This method is recommended for ores containing gibbsite and/or boehmite and when the residue from the dissolution of the test portion after silica volatilization is less than 1 % of the mass of the test portion. or b) sintering with sodium peroxide followed by

2、brief fusion and dissolution of the melt with sulfuric acid; NOTE - This method is recommended for ores containing diaspore and when the residue from the dissolution of the test por- tion after silica volatilization is greater than 1 % of the test portion. or c) fusion with sodium tetraborate/sodium

3、 carbonate flux followed by dissolution of the melt with sulfuric acid. NOTE - This method is suitable for all types of ore, Removal of silica by filtration to give a solution containing aluminium and other elements. Measurement of an aliquot por- tion and precipitation of aluminium and other elemen

4、ts except chromium, manganese and vanadium, by ammonium benzoate in acid solution. Filtration and dissolution of the precipitated benzoates in acid followed by precipitation of elements except aluminium by sodium hydroxide. Filtration of the precipitate followed by acid dissolution, reprecipitation

5、with sodium hydroxide and filtration to recover coprecipitated aluminium. Addition of an excess of EDNA to the combined filtrates and determination of aluminium content by back titration of the excess EDTA with zinc sulfate solution using xylenol orange as indicator. 4 Reagents During the analysis,

6、use only reagents of analytical reagent grade and only distilled water or water of equivalent purity. 4.1 Sodium peroxide (NazOz), powdered. NOTE - Sodium peroxide should be protected against humidity and should not be used once it has begun to agglomerate. 4.2 Sodium carbonate/sodium tetraborate fl

7、ux. Mix intimately 3 parts by mass of anhydrous sodium carbonate (NazCOs) and 1 part by mass of anhydrous sodium tetraborate (Na2B407). 4.3 Ammonium acetate, 266 g/l solution. Dissolve 250 g of ammonium acetate in 900 ml of water and adjust the pH to 6 by the addition of glacial acetic acid (Q 1,066

8、 g/ml). Dilute to 1 litre. 4.4 Ammonium benzoate, 100 g/l so!ution. NOTE - To obtain a clear solution after warming, it may be necessary to add up to 5 ml of ammonia solution (4.6). Filter if necessary to remove any particulate residue. 1 Copyright International Organization for Standardization Prov

9、ided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 6994-1986 (El 4.5 Hexamethylenetetramine (hexamine), 250 g/l sol- ution. 4.19 Zinc sulfate, standard volumetric solution, c(ZnS04.7H20) = 0,05 mol/l. Dissolve 25 g of hexamethylen

10、etetramine in 70 ml of water and dilute to 100 ml. Dissolve 14,5 g of zinc sulfate heptahydrate (ZnS0+7H20) in water, transfer to a 1000 ml one-mark volumetric flask, dilute to volume and mix. 4.6 Ammonia solution, (Q 0,9 g/ml), diluted 1 + 1. 4.19.1 Standardization procedure 4.7 Glacial acetic acid

11、 (Q 1,050 g/ml). 4.8 Hydrochloric acid (Q 1,17 g/ml), diluted 2+3. 4.19.1.1 Titration of EDTA solution with standard zinc sulfate solution 4.9 Sodium hydroxide, 160 g/l solution, Using a pipette, add 50 ml of the EDTA solution (4.18) to a 500 ml beaker and add 250 ml of water. Add 0,3 ml of the met

12、hyl orange indicator (4.20) and, if necessary, add the am- monia solution (4.6) drop by drop until the colour just changes to yellow. This solution shall be stored in a plastic bottle, 4.10 Sulfuric acid (Q I,84 g/ml), diluted I+ 1. 4.11 Sulfuric acid (Q 1,as in 4.19.1 .I. Add 0,5 ml of the xylenol

13、orange indicator (4.21) and titrate to the.end-point with the zinc sulfate solution (4.19). Record the titre ( V2L 4.17 Standard alumlnium solution. Dissolve approximately I,00 g, weighed to the nearest 0,000 1 g, of aluminium metal (not less than 99.9 %I in 66 ml of the hydrochloric acid (4.81, hea

14、ting if necessary. Cool and dilute to the mark in a 1000 ml one-mark volumetric flask. Calculate the equivalence factor A of the zinc sulfate solution, using the formula Calculate the equivalent aluminium oxide concentration a of the standard solution, in grams per litre,. using the equation 1 ml zi

15、nc sulfate solution (A) = P is the purity of aluminium used, in per cent. 4.20 Methyl orange indicator, 0,l g/l solution. 4.21 Xylenol orange indicator, 1 g/l solution. 4.18 Ethylenedlaminetetraacetic acid disodium salt dihydrate (EDTA), approximately 0,05 mol/l (18,6 g/l) stan- dard volumetric solu

16、tion. Prepare each month and store in a dark bottle. 2 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 6964-1666 (E) 5 Apparatus Ordinary laboratory apparatus, and NO

17、TE - The expression “independently” implies a change of the per- son carrying out the analysis. If the same person must carry out the analysis, the procedure should be carried out at different times. 5.1 Dishes, of inert material and sufficient size to take the re- quired quantity of sample at a lay

18、er density of 5 mg/mmz. 7.2 Test portion 5.2 Oven, electrically heated with a temperature-control device and mechanical convection, capable of maintaining a temperature of 105 V, is the volume, in miliilitres, of zinc sulfate solution (4.19) used. to titrate the blank test solution; V is the volume,

19、 in millilitres, of zinc sulfate solution (4.19) used to titrate the test solution; V, is the volume, in millilitres, of the aliquot portion taken in 7.7; m is the mass, in grams, of the test portion: K is the conversion factor found from the formula KLE!- 100-H where His the hygroscopic moisture co

20、ntent, as a percen- tage by mass, determined in accordance with IS0 8557. 8.2 General treatment of results 8.2.1 Precision A planned trial was carried out by ten countries with a total of sixteen laboratories participating. Two determinations were carried out on each of four samples. The repeatabili

21、ty, reproducibility and reproducibility index have been calculated and are presented in the table. 8.2.2 Acceptance of analytical values The analytical value for the test sample shall be accepted when the analytical value obtained for the corresponding certified reference material agrees with the ce

22、rtified value within the limit of the reproducibility index contained in the table, and when the difference between the two values for the test sample does not exceed 2,77 sw as calculated from the appropriate value of sw given in the table. 5 Copyright International Organization for Standardization

23、 Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 6994-1986 (El When the analytical value obtained for the certified reference material is outside the reproducibility index, an analysis shall be carried out simultaneously on

24、 one test sample and one certified reference material, with one blank test. The analytical value obtained for the certified reference material shall be examined for the acceptance of the value for the test sample, as above. If the value obtained for the certified reference material is again outside

25、the limits, the procedure shall be repeated with a different reference material of the same type of ore until two acceptable values for the test sample are obtained. When the range (absolute difference) of the two values for the test sample is greater than 2,77 s, additional analyses shall be carrie

26、d out on one test sample with one blank test simultaneously with an analysis of a certified reference material of the same type of ore. Acceptance of such additional values for the test sample shall be subject, in each case, to the accep- tability of the value obtained for the certified reference ma

27、terial. 8.23 Calculation of final result The final result is the arithmetical mean of the acceptable analytical values of the test sample calculated to the fourth decimal place and rounded off to the second decimal place as foilows: 11 When the figure in the third decimal place is less than 5, it is

28、 discarded and the figure in the second decimal place is kept unchanged. 2) When the figure in the third decimal place is 5 and there are figures other than 0 in the fourth decimal place, or when the figure in the third decimal place is greater than 5, the figure in the second decimal place is incre

29、ased by one. 3) When the figure in the third decimal place is 5 and there are no figures other than 0 in the fourth decimal place, the 5 is discarded and the figure in the second decimal place is kept unchanged if it is 0,2,4,6 or 8, and increased by one if itis1,3,5,7or9. 9 Test report The test rep

30、ort shall include the following: a) details necessary for the identification of the sample: b) reference to this International Standard; c) results of the analysis; d) reference number of the results: e) any characteristics noticed during the determination and any operations not specified in the Int

31、ernational Stan- dard which may have had an influence on the results. Table - Precision data for aluminium determinations Sample M-r/12/5 MT112112 MT/l214 NBS 696 Ore type Mean AI,O, content % (m/m) Gibbsite (19,5 % Fe,O,) 46.62 _ Diaspore (21,7 % Fe,O, 4.0 % SiO,) BoehmiWgibbsite blend Gibbsite 52,

32、46 53,39 wa Components of standard deviation SW sb 0,131 0,212 0,137 0,306 0,120 0,126 0,051 0,149 Reproducibility index 2s 030 0.67 0,35 0,31 l Certificate value q, is the between-laboratories standard deviation. Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-