BS 6783-12-1992 Sampling and analysis of nickel ferronickel and nickel alloys - Method for the determination of phosphorus in nickel alloys by molybdenum blue molecular absorption .pdf

1、BRITISH STANDARD BS 6783-12: 1992 ISO 9388:1992 Sampling and analysis of nickel, ferronickel and nickel alloys Part 12: Method for the determination of phosphorus in nickel alloys by molybdenum blue molecular absorption spectrometry UDC 669.245:543.422:546.18BS6783-12:1992 This British Standard, hav

2、ing been prepared under the directionof the Non-ferrous Metals Standards Policy Committee, was published underthe authority of theStandards Board and comesinto effect on 15December 1992 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference NFM/10 Draft for

3、 comment 91/39452 DC ISBN 0 580 21393 5 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Non-ferrous Metals Standards Policy Committee (NFM/-) to Technical Committee NFM/10, upon which the following bodies were represented: Association of

4、 Bronze and Brass Founders British Non-ferrous Metals Federation British Steel Industry Department of Trade and Industry (Laboratory of the Government Chemist) Engineering Equipment and Materials Users Association Institute of British Foundrymen London Metal Exchange Ministry of Defence Nickel Devel

5、opment Institute Non-ferrous Metal Stockists Stainless Steel Fabricators Association of Great Britain Steel Casting Research and Trade Association Coopted members Amendments issued since publication Amd. No. Date CommentsBS6783-12:1992 BSI 10-1999 i Contents Page Committees responsible Inside front

6、cover National foreword ii 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Sampling and sample preparation 2 7 Procedure 2 8 Expression of results 4 9 Interferences 4 10 Test report 4 Annex A (informative) Examples of composition of some nickel alloys 6 Table 1 Mass of

7、sample to be taken 2 Table 2 Nominal composition of test samples 4 Table 3 Results of statistical analysis 5 Table A.1 Examples of composition of some nickel alloys 6 List of references Inside back coverBS6783-12:1992 ii BSI 10-1999 National foreword This Part of BS 6783 has been prepared under the

8、direction of the Non-ferrous Metals Standards Policy Committee. It is identical with ISO 9388:1992 Nickel alloys Determination of phosphorus content Molybdenum blue molecular absorption spectrometric method published by the International Organization for Standardization (ISO). At present this Britis

9、h Standard consists of 12 Parts all concerned with analysis of nickel, ferronickel and nickel alloys. Further International Standards are in preparation on sampling and analysis of nickel, ferronickel and nickel alloys and, when available, these will be published as further Parts of this British Sta

10、ndard. 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 not of itself confer immunity from legal obligations. Cross-references International Sta

11、ndard Corresponding British Standard ISO 1042:1983 BS 1792:1982 Specification for one-mark volumetric flasks (Identical) ISO 5725:1986 BS 5497 Precision of test methods Part 1:1987 Guide for the determination of repeatability and reproducibility for a standard test method by inter-laboratory tests (

12、Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on th

13、e inside front cover.BS6783-12:1992 BSI 10-1999 1 1 Scope This International Standard specifies a molecular absorption spectrometric method for the determination of the phosphorus content of nickel alloys in the range 0,001 % (m/m) to 0,025 % (m/m). Typical compositions of some nickel alloys are giv

14、en in Annex A. Chromium(III) and silica cause interference which is eliminated in the procedure. See clause 9. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, th

15、e editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of cur

16、rently valid International Standards. ISO 1042:1983, Laboratory glassware One-mark volumetric flasks. ISO 5725:1986, Precision of test methods Determination of repeatability and reproducibility for a standard test method by inter-laboratory tests. 3 Principle Dissolution of a test portion in nitric

17、and hydrochloric acids. Removal of hydrochloric acid by fuming with sulfuric acid, and oxidation of chromium(III) to chromium(VI) with ammonium peroxydisulfate. Precipitation of iron(III) phosphate and redissolution of the precipitate in a hydrofluoric-nitric acid mixture. Addition of boric, tartari

18、c, and sulfamic acids to complex free fluoride, eliminate arsenic interference, and remove oxides of nitrogen. Formation and extraction of molybdophosphoric acid into isobutyl alcohol, reduction of the, heteropoly acid to molybdenum blue and back-extraction into an aqueous phase. Measurement of the

19、absorbance of the aqueous solution at 700 nm. 4 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Nitric/hydrochloric acid, mixture. WARNING This acid mixture is highly corrosive and uns

20、table. Noxious gases (chlorine) are liberated on standing. It shall be prepared and used in a fume cupboard and shall not be kept in a closed container. Carefully mix 25 ml of nitric acid ( 20= 1,41 g/ml) and 125 ml of hydrochloric acid ( 20= 1,18 g/ml). This mixture should be prepared just before u

21、se. 4.2 Hydrofluoric acid, 20= 1,15 g/ml, 48 % (m/m) HF. WARNING Hydrofluoric acid is extremely irritating and corrosive to skin and mucous membranes, producing severe skin burns which are slow to heal. In the case of contact with skin, wash well with water and seek medical advice. 4.3 Sulfuric acid

22、, 20= 1,84 g/ml, diluted 1 + 1. Slowly, and with constant stirring, add 100 ml of sulfuric acid to 100 ml of water. 4.4 Boric acid, solution. Dissolve 40 g of boric acid (H 3 BO 3 ) in 1 litre of water and mix. 4.5 Oxalic acid, solution. Dissolve 1 g of oxalic acid dihydrate (COOH) 2 2H 2 O in 100 m

23、l of water and mix. 4.6 Sulfamic acid, solution. Dissolve 5 g of sulfamic acid (NH 2 SO 3 H) in 100 ml of water and mix. 4.7 Tartaric acid, solution. Dissolve 10 g of tartaric acid (CHOHCOOH) 2 in100 ml of water and mix. 4.8 Chloroform (CHCl 3 ). 4.9 Isobutyl alcohol, (2-methyl-1-propanol) (CH 3 ) 2

24、 CHCH 2 OH. 4.10 Ammonia, solution, 20= 0,89 g/ml. 4.11 Ammonium nitrate, solution. Dissolve 5 g of ammonium nitrate (NH 4 NO 3 ) in500ml of water. 4.12 Ammonium peroxydisulfate, solution. Dissolve 20 g of ammonium peroxydisulfate (NH 4 ) 2 S 2 O 8 in water and dilute to 200 ml. Prepare a fresh solu

25、tion every three days. 4.13 Iron(III) nitrate, solution. Dissolve 7,2 g of iron(III) nitrate nonahydrate Fe(NO 3 ) 3 9H 2 O in about 75 ml of water containing3 ml of nitric acid ( 20= 1,41 g/ml), dilute to 100 ml with water and mix. 4.14 Silver nitrate, solution. Dissolve 3 g of silver nitrate (AgNO

26、 3 ) in 200 ml of water. Store in a dark glass bottle.BS6783-12:1992 2 BSI 10-1999 4.15 Sodium molybdate, solution. Dissolve 10 g of sodium molybdate dihydrate (Na 2 MoO 4 2H 2 O) and 8 g of sodium hydroxide (NaOH) in 200 ml of water. 4.16 Sodium chloride, wash solution. Dissolve 23 g of sodium chlo

27、ride (NaCl) in water, add 50 ml of hydrochloric acid ( 20= 1,18 g/ml) and dilute to about 900 ml. Add 60 ml of isobutyl alcohol(4.9) and shake to dissolve. Dilute to a final volume of 1 litre and mix. 4.17 Reducing solution 4.17.1 Dissolve 10 g of stannous chloride dihydrate (SnCl 2 2H 2 O) in 25 ml

28、 of hydrochloric acid ( 20 =1,18 g/ml) and heat until dissolved. Cool to ambient temperature and dilute to 50 ml with water. The solution is stable for at least one week when kept in a stoppered flask. 4.17.2 Transfer 5 ml of this solution to a 250 ml one-mark volumetric flask, add 10 ml of the sulf

29、uric acid (4.3), make up to the mark with water and mix. Prepare a fresh solution each day. 4.18 Phosphorus, standard reference solution(100mg/l). Transfer exactly 0,439 4 g of potassium dihydrogen phosphate (KH 2 PO 4 ) to a 1 000 ml one-mark volumetric flask, add 100 ml of water and 5 ml of nitric

30、 acid ( 20= 1,41 g/ml) diluted 1 + 1. Dissolve the salt, make up to the mark with water and mix. 5 Apparatus Ordinary laboratory glassware, and 5.1 Plastics beakers, of capacity 250 ml and usable up to 150 C. Polymethylpentene or fluorocarbon polymers have been found satisfactory. 5.2 Plastics filtr

31、ation funnels 5.3 Separating funnels, of capacity 125 ml. Two funnels are required for the analysis of each test sample. Polytetrafluoroethylene stopcocks and plastics stoppers are preferred. 5.4 One mark volumetric flasks, complying with the requirements of ISO 1042, class A. 5.5 Mechanical micropi

32、pettes, of capacities1004l,250 4l and 500 4l. 5.6 Molecular absorption spectrometer, suitable for measuring absorbance at 700 nm and equipped with optically matched 1 cm or 2 cm glass cells. 6 Sampling and sample preparation 6.1 Sampling and preparation of the laboratory sample shall be carried out

33、according to normal agreed procedures or, in case of dispute, the relevant International Standard. 6.2 The laboratory sample is normally in the form of millings or drillings and no further preparation of the sample is necessary. 6.3 If it is suspected that the laboratory sample is contaminated with

34、oil or grease from the milling or drilling process, it shall be cleaned by washing with high purity acetone and drying in air. 6.4 If the laboratory sample contains particles or pieces of widely varying sizes, the test portion should be obtained by riffling. 7 Procedure 7.1 Test portion and preparat

35、ion of test solution 7.1.1 Weigh a test portion containing between 3 4g and 50 4g of phosphorus according to Table 1, and transfer it to a 150 ml glass beaker. Table 1 Mass of sample to be taken 7.1.2 Add 7 ml of the acid mixture (4.1), cover the beaker and warm. Remove the beaker from the heat and

36、allow the reaction to proceed and subside. Heat again to complete the dissolution. 7.1.3 Add 5 ml of the sulfuric acid (4.3) and evaporate to dense fumes. Do not evaporate to dryness. Cool to room temperature and dissolve the salts in 5 ml of nitric acid ( 20= 1,41 g/ml) and 30 ml of water. Transfer

37、 the solution, which may contain hydrolysed products of refractory metals, quantitatively to a 400 ml beaker. Use a rubber policeman if necessary. NOTE 1Usually, the dissolution is rapid and no extensive heating is required. Some alloys, particularly those high in copper, are best dissolved in 7 ml

38、of nitric acid ( 20= 1,41 g/ml), diluted 1 + 1. In such instances, omit 7.1.3 and proceed as directed in 7.2. Expected phosphorus content Mass of sample Weighing accuracy % (m/m) g g 0,001 to 0,01 0,29 to 0,31 0,005 0,01 to 0,025 0,19 to 0,21 0,002BS6783-12:1992 BSI 10-1999 3 7.2 Separation of chrom

39、ium 7.2.1 Dilute the solution to 150 ml, add 3 ml of the iron(III) nitrate solution (4.13), and heat almost to boiling. Add 10 ml of the silver nitrate solution(4.14) and 30 ml of the ammonium peroxydisulfate solution (4.12). Boil the mixture for10 min to 15 min to decompose the excess oxidant. Dilu

40、te to 250 ml with water and add, while stirring, the ammonia solution (4.10) until a permanent precipitate of iron(III) hydroxide forms. Add 15 ml of ammonia solution in excess and digest the hot mixture for about 15 min. Filter the precipitate through a fast filter paper containing some wet filter

41、pulp. Wash the precipitate and filterthorougly with the ammonium nitrate solution(4.11) until all of the yellow colour due to the chromate ions has been removed. 7.2.2 Transfer the filter with the precipitate to a plastics beaker (5.1) containing 2 ml of hydrofluoric acid (4.2). Wash the precipitati

42、on beaker with 10 ml of nitric acid ( 20= 1,41 g/ml) diluted 1 + 1 and add the washings to the plastics beaker. Heat carefully to dissolve the precipitate, and break up the filter with a plastics stirring rod. Filter through an 11 cm medium speed filter and plastics funnel into a100ml plastics beake

43、r. Wash twice with 5 ml portions of water and then once with 30 ml of the boric acid solution (4.4). Finish washing the filter with water so that the total volume of the filtrate does not exceed 60 ml to 70 ml. NOTE 2It is important to ensure that all the chromium is oxidized to chromium(VI) before

44、the precipitation, and to wash the precipitate and filter until it is completely free of chromium(VI). The filtration and washing of the precipitate of hydrous oxides is very fast in the presence of filter pulp. 7.3 Extraction of molybdophosphoric acid 7.3.1 Transfer the filtrate to a separating fun

45、nel(5.3). Add 2 ml of the tartaric acid solution(4.7), 1 ml of the sulfamic acid solution(4.6), and 10 ml of the sodium molybdate solution (4.15). Mix by swirling, add 20 ml of the isobutyl alcohol (4.9) and extract by shaking the funnel vigorously for 2 min. Allow the phases to separate and transfe

46、r the lower aqueous layer into a second separating funnel. Add, to this aqueous phase, 5 ml of sodium molybdate solution and 10 ml of isobutyl alcohol. Shake vigorously for 2 min, allow the phases to separate and discard the lower aqueous phase. Combine the remaining organic phase with that in the f

47、irst separating funnel. Swirl, allow to settle and discard any residual aqueous phase which may separate on standing. 7.3.2 Wash the combined extracts by adding 20 ml of the sodium chloride wash solution (4.16) and shaking for 30 s. Drain off and discard the lower aqueous phase. Repeat the washing o

48、f the organic phase twice more, each time using 20 ml of the sodium chloride wash solution. Discard the aqueous washings. 7.4 Molybdenum blue development To the washed extract add, in order, 40 ml of the chloroform (4.8), 30 ml of water, 10 ml of the diluted reducing solution (4.17.2), and 2 ml of t

49、he oxalic acid solution (4.5). Without delay, shake for 1 min. Allow the phases to separate and discard the heavier chloroform layer. Transfer the blue aqueous solution into a 100 ml one-mark volumetric flaskcontaining 5 ml of hydrochloric acid ( 20 =1,18g/ml) diluted 1 + 1. Rinse the funnel with water and dilute the solution in the flask to the mark. Mix and allow to stand for at least 20 min before measurement. NOTE 3The mixtures should not be left standing after the reducing and oxalic acid solutions have been added.