ISO-4689-1986.pdf
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1、International Standard 4689 0 N 4 a!i! INTERNATLONAL ORGANIZATION FOR STANDARDIZATlON*MEXAYHAPOAHAR OPI-AHHBAl prepare immediately before use. 4.11 Barium chloride (BaClz.2HzO), 166 g/l solution. Dissolve 166 g of crystalline barium chloride dihydrate (BaClz.2HzO) in 1 litre of water, cover and heat
2、 to boiling point. Keep warm on a water bath for a minimum of 2 h and allow to cool to room temperature overnight. Store the solution in a plastics bottle and before each use, filter the required volume through a close-texture filter paper. 4.12 Hydrochloric acid wash solution, containing barium chl
3、oride. Filter 10 ml of barium chloride solution (4.11) through a close- texture filter paper, and dilute to 1 666 ml with hydrochloric acid solution (4.7). 1 -,-,- 4.13 Sodium nitrate (NaNOs), saturated solution. 4.14 Sodium carbonate (Na$Os), 20 g/l solution. Store in a plastics bottle. 4.15 Ammoni
4、um thiocyanate (NH 8.1 Calculation of sulfur content a, is the within-laboratory standard deviation; The sulfur content, ws, is calculated as a percentage by mass, to five decimal places, using the equation w (%) = (ml - + - ( m3 - m411 x 0,137 4 x 160 S m5 = h - m2) - h3 - mqi x 13,74 *a (I) m5 whe
5、re ml is the mass, in grams, of the platinum crucible contain- ing barium sulfate from the test portion; m2 is the tare, in grams, of the platinum crucible used for the determination; mg is the mass, in grams, of the platinum crucible for the blank test; m4 is the tare, in grams, of the platinum cru
6、cible for the blank test; m5 is the mass, in grams, of the test portion (7,3); 0,1374 is the mass ratio of sulfur in barium sulfate. 8.2 General treatment of results M.1 Repeatability and permissible tolerance The precision of this analytical method is expressed by the following regression equations
7、: I) r = 0,026 x -I? 0,004 . I I (2 P = 0,027 X -I- 0,006 I (3) Qr = 0,009 x -I- 0,002 I I (4) QL = 0,607x -I- 0,002 . . (5) where X Is the sulfur content, expressed as a percentage by mass, of the predried test sample, calculated as follows: - within-laboratory equations (2, 4); the arithmetic mean
8、 of the duplicate values, - between-laboratories equations (3, 5): the arith- metic mean of the final results (8,2,3I of the two labora- tories; r is the permissible tolerance within a laboratory (repeatability); a is the between-laboratories standard deviation. 8.2.2 Acceptance of analytical values
9、 The result obtained for the certified reference material shall be such that the difference between this result and the certified value of the certified reference material is statistically insignifi- cant. For a certified reference material that has been analysed by at least 10 laboratories using me
10、thod(s) that are comparable both in accuracy and precision with this method, the following condition may be used to test the significance of the dif- ference: / n J SL WC $c + G I4-42 N “2, + aL2+ ; . . . (6) c where A, is the certified value; A is the result or the mean of results obtained for the
11、cer- tified reference material; sLc is the between-laboratories standard deviation of the certifying laboratories; swc is the within-laboratory standard deviation of the cer- tifying laboratories; nWc is the average number of replicate determinations in the certifying laboratories: N, is the number
12、of certifying laboratories: n is the number of replicate determinations on the reference sample (In most cases, n = 1) ; at, and or are as defined in 8.2.1. If condition (6) is satisfied, i.e. if the left-hand side of the condi- tion is less than or equal to the right-hand side, then the dif- ferenc
13、e IA, c Al is statistically insignificant; otherwise, it is statistically significant. When the difference is significant, the analysis shall be repeated, simultaneously with an analysis of the test sample. If the difference Is again significant, the procedure shall be repeated using a different cer
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