1、International Standard (! 8556 0 N 4 d!l!l INTERNATIONAL ORGANIZATION FOR STANDAFiDIZATION*MEX/lYHAPOAHAR OPrAHH3AUMR IlO CTAHAAPTbi3AUMWORGANlSATlON INTERNATIONALE DE NORMALISATION Aluminium ores - Determination of phosphorus content - Molybdenum blue spectrophotometric method Minerais alumineux -
2、Dosage du phosphore - M 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 test portion. or b) sintering with sodium peroxide followed by a brief fu- sion. Di
3、ssolution 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 is greater than 1 % of the mass of the test portion. Dehydration of silica, dissolution of salts, filtration and ignition of the im
4、pure silica. Removal of the silica by evaporation with hydrofluoric and sulfuric acids. Fusion with sodium carbonate and sodium tetraborate, dissolution with hydrochloric acid and combination with the main solution. Addition of molybdate to convert the phosphate to molyb- dophosphate complex, and re
5、duction to molybdenum blue with ascorbic acid. Spectrophotometric measurement of the absorbance of the molybdenum blue complex at approximately 710 nm. 4 Reagents During the analysis, use only reagents of recognized analytical reagent grade, and only distilled water or water of equivalent purity. 4.
6、1 Sodium peroxide (Na,O,), powder. 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 flux. Mix intimately 3 parts by mass of anhydrous sodium carbonate (Na m2 is the mass, in milligrams, of dip
7、hosphorus pentoxide contained in the aliquot portion of test solution, or diluted test solution, (7.5.4) determined by using the calibration graph, after correcting for the blank and, if necessary, to a basis of an optical pathlength of IO mm; f is the dilution factor, equal to 10, if diluted test s
8、olution has been used; V is the volume of the aliquot portion of test solution, or diluted test solution (7.5.4). 8.2 General treatment of results 8.2.1 Precision A planned trial was carried out by nine countries with a total of thirteen laboratories participating. Two determinations were carried ou
9、t on each of four samples. The repeatability, repro- ducibility and reproducibility index have been calculated and are presented in table 2. 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 certi
10、fied Table 2 - Precision data for phosphorus determinations Mean Components of standard Pi!% deviation Sample content % imInd ,r, Sb MT/1216 0,056 0,005 0,003 MT/12/9 0,381 0,007 0,013 MT/l2/12 0,558 0,007 0,006 MT/l217 3,692 0,057 0,060 s, is the within-laboratory standard deviation; .q, is the bet
11、ween-laboratories deviation. Reproducibilii index 2 s 0,011 0,030 0,021 0,196 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 8556-1986 (El reference material agrees
12、with the certified value within the limit of the reproducibility index contained in table 2, 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 table 2. When the analytical value obtained for the certifi
13、ed reference material is outside the reproducibility index, an analysis shall be carried out simultaneously on one test sample and one certified reference material, with one blank test. The analytical value ob- tained for the certified reference material shall be examined for the acceptance of the v
14、alue for the test sample, as above. If the value obtained for the certified reference material is again out- side 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 (abso
15、lute difference) of the two values for the test sample is greater than 2,77 s, additional analyses shall be carried out on one test sample with one blank test in accor- dance with the procedure specified in the annex, simul- taneously with an analysis of a certified reference material of the same ty
16、pe 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 material. 1) When the figure in the fourth decimal place is less than 5, it is discarded and the figure in the third decimal pl
17、ace is kept unchanged. 2) When the figure in the fourth decjmal place is 5 and there are figures other than 0 in the fifth decimal place, or when the figure in the fourth decimal place is greater than 5, the figure in t.he third decimal place is increased by one. 3) When the figure in the fourth dec
18、imal place is 5 and there are no figures other than 0 in the fifth decimal place, the 5 is discarded and the figure in the third decimal place is kept unchanged if it is 0,2,4,6 or 8, and increased by one if it is 1, 3, 5, 7 org. 9 Test report The test report shall include the following information
19、: al details necessary for the identification of the sample; b) reference to this International Standard; cl the result of the analysis; 8.2.3 Calculation of final result d) reference number of the result; The final result is the arithmetical mean of the acceptable analytical values of the test samp
20、le calculated to the fifth decimal place and rounded off to the third decimal place as follows : e) any characteristics noticed during the determination and any operations not specified in this International Stan- dard which may have had an influence on the result. 5 Copyright International Organiza
21、tion for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 8556-1986 (El Annex Flowsheet of the procedure for the acceptance of test results (This annex forms part of the Standard.) Perform xl, x2 NO Perform x
22、3 .y= Xl + x2 + x3 3 L - NO e Perform x3, x4 G Perform x4 Range of x1, x2, x3, x4 4 1,3 r xc Xl + x2 + x3 + x4 4 H = Median of XI, 2, x3, 4 r = 2,77 sw s, as defined in 8.2.1. 6 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
