BS 6200-3 16 3-1991 Sampling and analysis of iron steel and other ferrous metals - Methods of analysis - Determination of lead - Steel spectrophotometric method for trace amounts《铁.pdf

1、BRITISH STANDARD BS 6200-3.16.3: 1991 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.16 Determination of lead Subsection 3.16.3 Steel: spectrophotometric method for trace amountsBS6200-3.16.3:1991 This British Standard, having been prepared under

2、the directionof the Iron and Steel Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 29November1991 BSI09-1999 The following BSI references relate to the work on this standard: Committee reference ISM/18 Draft for comment 91/35214 DC ISBN 0 58

3、0 19945 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) to Technical Committee ISM/18, upon which the following bodies were represented: BCIRA British Steel Industry Department of Trade

4、 and Industry (Laboratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS6200-3.16.3:1991 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle

5、1 3 Reagents 1 4 Apparatus 1 5 Sampling 1 6 Procedure 2 7 Calculation and expression of results 3 8 Test report 4 Table 1 Precision data 4 Table 2 Predicted valves of r and R 4 Publications referred to Inside back coverBS6200-3.16.3:1991 ii BSI 09-1999 Foreword This Subsection of BS6200has been prep

6、ared under the direction of the Iron and Steel Standards Policy Committee and supersedes method3for the determination of lead in BSI Handbook No. 19, to which it is technically equivalent. BS6200is a multipart British Standard, covering all aspects of the sampling and analysis of iron, steel and oth

7、er ferrous metals. A list of contents, together with general information, is given in Part1. 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 no

8、t of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1to4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will

9、 be indicated in the amendment table on the inside front cover.BS6200-3.16.3:1991 BSI 09-1999 1 1 Scope This Subsection of BS6200describes a spectrophotometric method for the determination of trace amounts of lead in steel. The method is applicable to lead contents from0.0005%(m/m) to0.05 % (m/m). N

10、OTEThe titles of publications referred to in this Subsection of BS6200 are listed on the inside back cover. 2 Principle From an oxidized hydrochloric acid solution of the steel, iron is removed by extraction into amyl acetate. Lead is extracted into chloroform as its diethyldithiocarbamate complex f

11、rom a citrate-cyanide solution. The lead complex is selectively extracted in hydrochloric acid solution to separate it from bismuth. It is then converted to its dithizone complex in ammoniacal citrate-cyanide solution and extracted in chloroform. The determination is completed spectrophotometrically

12、. 3 Reagents NOTEWhere available lead-free reagents should be used. During the analysis use only reagents of recognized analytical grade and which are known to give a very low lead blank. Use only grade3water as specified in BS3978. 3.1 Ammonia solution, density = 0.91g/mL. 3.2 Ammonia solution, = 0

13、.91g/mL, diluted1+1. 3.3 Ammonia solution, = 0.91g/mL, diluted1+3. 3.4 Ammonium citrate. Dissolve25g of citric acid, H 8 C 6 O 7 H 2 O, in the minimum amount of water. Neutralize with ammonia solution (3.1), dilute to100mL and mix. 3.5 Amyl acetate NOTEThis solvent is NOT pentyl acetate, (n-amyl ace

14、tate), but consists principally of3-methylbutyl acetate with a small proportion of 2-methylbutyl acetate. 3.6 Chloroform 3.7 Citric acid, 250g/L solution. Dissolve25g of citric acid, H 8 C 6 O 7 .H 2 O), in water, dilute to100mL and mix. 3.8 Dithizone, 0.05 g/L solution. Dissolve0.005g of dithizone

15、in chloroform, dilute to100mL with chloroform and mix. 3.9 Hydrochloric acid, = 1.16 g/mL to1.18 g/mL. 3.10 Hydrochloric acid, = 1.16g/mL to1.18g/mL, diluted1 + 19. 3.11 Hydroxylammonium chloride, 10g/L solution. Dissolve1g of hydroxylammonium chloride in water, dilute to100mL and mix. 3.12 Lead, st

16、andard solution, 0.01mg lead per millilitre. Wash approximately 1g of lead, of purity at least99.9%(m/m), in boiling hydrochloric acid (3.9) diluted1 + 7 (V/V). Wash with water, rinse in acetone and dry in a vacuum desiccator. Weigh, to the nearest0.001g, 0.5g of the clean lead and dissolve in20mL o

17、f nitric acid (3.14). Boil to remove nitrous fumes, and cool. Transfer to a1L volumetric flask, dilute to the mark and mix. Transfer20mL of this lead solution (0.5mg of lead per millilitre) by means of a pipette to a1L volumetric flask and mix. 3.13 Nitric acid, = 1.42 g/mL. 3.14 Nitric acid, = 1.42

18、 g/mL, diluted1 + 4. 3.15 Perchloric acid, = 1.54 g/mL. 3.16 Potassium cyanide, 100 g/L solution. Dissolve25g of potassium cyanide in water, dilute to250mL, and mix. 3.17 Potassium cyanide, 5g/L solution. Dissolve2.5g of potassium cyanide in water, dilute to500mL, and mix. 3.18 Sodium diethyldithioc

19、arbamate, 2g/L solution. Dissolve0.2g sodium diethyldithiocarbamate in water, dilute to100mL and mix. 3.19 Sodium hydroxide, 2g/L solution. Dissolve0.2g of sodium hydroxide in water, dilute to100mL and mix. Prepare and store this solution in a polyethylene container. 3.20 Sulfuric acid, = 1.84g/mL,

20、diluted1 + 1. To100mL of water add cautiously125mL of sulfuric acid = 1.84g/mL, stirring constantly. Cool, dilute to250mL and mix. 3.21 Thymol blue, 0.4g/L solution. Dissolve0.1g of thymol blue by warming with4mL of sodium hydroxide solution (3.19) and5mL of ethanol. Add50mL of ethanol, dilute to250

21、mL with water and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with classA of BS846, BS1583or BS1792, as appropriate. 4.3 Spectrophotometer 4.4 Cells, having an optical path length of1cm. 5 Sampling Carry out sampling in accordance with BS1837. NOTEBS620

22、0-2, which will supersede BS1837, is currently in preparation. On its publication, this Subsection will be amended to include sampling in accordance with BS6200-2.BS6200-3.16.3:1991 2 BSI 09-1999 6 Procedure 6.1 Test portion Weigh, to the nearest0.001g, a test portion of0.5g. 6.2 Blank test In paral

23、lel with the determination and following the same procedure, carry out a blank test using the same quantities of all reagents. NOTEA typical blank value for this method in the range0.0005%(m/m) to 0.010%(m/m) lead is equivalent to approximately0.0005%(m/m) lead. 6.3 Determination 6.3.1 Preparation o

24、f the test solution 6.3.1.1 Place the test portion in a250mL conical beaker. Add5mL of hydrochloric acid (3.9) and1mL of nitric acid (3.13), and heat gently until solvent action ceases. Add0.5mL of perchloric acid(3.15), evaporate to dryness and bake for10min. For samples containing niobium or titan

25、ium use8mL of sulfuric acid (3.20) instead of the perchloric acid, evaporate until slight fumes of sulfur trioxide appear, and cool. NOTEThese and all subsequent reagent additions should be made by means of a safety pipette or burette. 6.3.1.2 Redissolve the residue in 10mL of hydrochloric acid (3.9

26、), cool and transfer to a150mL separating funnel. Rinse the beaker three times with3mL portions of hydrochloric acid (3.9) and combine with the solution in the separating funnel. Add25mL of amyl acetate (3.5) and shake vigorously for2min. Allow the layers to separate and run off the lower (acid) lay

27、er into a250mL conical beaker. Wash the amyl acetate layer twice by shaking with2mL portions of hydrochloric acid(3.9), allowing the layers to separate, and combining the acid layers with the first acid extract. 6.3.2 Removal of bismuth NOTEFor unalloyed and low-alloy steels where bismuth is known t

28、o be absent the directions given in6.3.2 may be omitted. Add0.5 mL of perchloric acid (3.15) and a few drops of nitric acid (3.13) to the acid extract, cover the beaker and evaporate until fumes appear. Cool, add2mL of hydrochloric acid (3.9) and10mL of hydroxylammonium chloride solution (3.11). War

29、m to redissolve any salts, then boil for2min. Add20mL of ammonium citrate solution (3.4), heat to incipient boiling and simmer for3min. Cool, neutralize with ammonia solution (3.2) to pH7.5to pH9.0, testing the solution with a narrow-range pH testpaper, then transfer to a200mL separating funnel mark

30、ed at100mL and dilute to the mark. Add 20 mL of potassium cyanide solution (3.16). For samples containing more than30%(m/m) of nickel add an extra5mL of potassium cyanide solution(3.16) for every additional10%of nickel. Add10mL of sodium diethyldithiocarbamate solution (3.18), mix and allow to stand

31、 for2min. Extract the lead complex three times by shaking with successive additions of15mL, 10mL, and10mL of chloroform (3.6), each time allowing the layers to separate and combining the chloroform extracts in a250mL conical beaker. Transfer the combined chloroform extracts to a100mL separating funn

32、el and shake with25mL of hydrochloric acid (3.10). Allow the layers to separate and run off the lower (chloroform) layer into a second100mL separating funnel. Repeat the extraction from the chloroform by shaking with a second portion of25mL of hydrochloric acid (3.10). Allow the layers to separate,

33、run off and discard the lower (chloroform) layer. Combine the two aqueous layers in a250mL conical beaker. 6.3.3 Treatment of the lead solution Add 1 mL of nitric acid (3.13), 2mL of perchloric acid (3.15) and4mL of sulfuric acid (3.20), cover the beaker, then evaporate to fumes of sulfur trioxide.

34、Cool, add10mL of hydroxylammonium chloride solution (3.11) and 2.5mL of hydrochloric acid (3.9), heat gently for5min and cool. Rinse the cover and walls of the beaker with5mL of water, add1mL of citric acid solution (3.7), three drops of thymol blue indicator (3.21), then add ammonia solution (3.1)

35、until the colour of the indicator changes to blue. Add5mL of ammonia solution (3.2) and cool. If the sample contains more than0.01%(m/m) lead, dilute the solution to 50mL in a volumetric flask and take a suitable aliquot for the test. It is essential that the blank test is fractionated in the same w

36、ay. 6.3.4 Development of the colour Transfer the solution or aliquot to a150mL separating funnel marked at 50mL and rinse with water. Add5mL of potassium cyanide solution(3.16) and dilute to the mark.BS6200-3.16.3:1991 BSI 09-1999 3 From a burette, add8.0mL of chloroform (3.6) and then add dithizone

37、 solution (3.8) (also from a burette)1.0mL at a time, shaking between each addition, until an excess of dithizone is indicated by the colour of the chloroform layer changing to a purple-blue. Add2.0mL of dithizone solution (3.8) in excess, then sufficient chloroform (3.6) to bring the total amount o

38、f chloroform and dithizone solution to15.0mL. Shake vigorously for2min, allow the two layers to separate, then run the chloroform layer into another separating funnel containing40mL of potassium cyanide solution(3.17) and10mL of ammonia solution(3.3). Shake for1min and allow the layers to separate.

39、Filter the chloroform layer through a5.5cm rapid filter paper into a clean dry1cm cell, discarding the initial few drops. 6.3.5 Spectrophotometric measurement Set the spectrophotometer (4.3) to zero absorbance in relation to water. Measure the absorbance of the test solution and the blank at a wavel

40、ength of510nm. Convert the readings obtained to milligrams of lead by reference to the calibration graph (6.4). 6.4 Establishment of the calibration graph To a series of six250mL conical beakers, add0.0mL, 1.0mL, 2.0mL, 3.0mL, 4.0mL, and5.0mL of lead solution (3.12). Add5mL of hydrochloric acid (3.9

41、) and1mL of nitric acid (3.13). Add5mL of perchloric acid (3.15) and evaporate the solutions to dryness. Continue by following the procedure given in6.3.1.2 to6.3.5, and prepare a calibration graph by plotting the absorbance readings obtained against the equivalent milligrams of lead. 7 Calculation

42、and expression of results 7.1 Calculation Calculate the lead content, expressed as percentage by mass, from the equation: where If an aliquot of volume V (in mL) was taken from50mL in6.3.3, multiply the lead content calculated from the equation by the factor F, whereF =50/V. 7.2 Precision 7.2.1 Prec

43、ision data A planned trial of this method was carried out by five analysts, each from a different laboratory; six tests were carried out by each analyst on each of six samples. From the results obtained, the95%confidence limits (2s) have been calculated in accordance with BS5497-1 and are given in T

44、able 1. The difference between two single results found on identical material by one analyst using the same apparatus within a short time interval will exceed the repeatability r not more than once in20cases, on average, in the normal and correct operation of the method. The difference between two s

45、ingle and independent results found by two operators working in different laboratories on identical test material will exceed the reproducibility R on average, not more than once in20cases in the normal and correct operation of the method. 7.2.2 Regression data Statistical analysis of the results sh

46、ows a logarithmic relationship between lead content and the values of repeatability, r, and reproducibility, R, summarized by the following logarithmic equations: log r = 0.5385 log Pb 2.0810 correlation coefficient = 0.990 log R = 0.4642 log Pb 2.0817 correlation coefficient = 0.940 with concentrat

47、ion of lead content Pb, r and R expressed as%(m/m). lead content m 1 m 0 10 m - = m 1 is the mass of lead found in the test solution (in mg); m 0 is the mass of lead found in the blank solution (6.2) (in mg); m is the mass of the test portion (6.1) (in g).BS6200-3.16.3:1991 4 BSI 09-1999 Table 1 Pre

48、cision data The predicted values of r and R calculated from these equations are shown in Table 2. Table 2 Predicted values of r and R 8 Test report The test report shall include the following information: a) all information necessary for the identification of the sample, the laboratory and the date

49、of analysis; b) the method used by reference to this Subsection of BS6200; c) the results, and the form in which they are expressed; d) any unusual features noted during the determination; e) any operation not specified in this British Standard, or any optional operation which may have influenced the results. Alloy type Lead content Repeatability r Reproducibility R % (m/m) 18 % Cr, 9 % Ni, 2.5 % Mo stainless steel, (all m/m) 0.0008 0.00020 0.00046 18 % Cr, 9 % Ni, 1 % Mo, 1.5 % Nb stainless steel 0.0011 0.00025 0.0003