BS 6783-13-1992 Sampling and analysis of nickel ferronickel and nickel alloys - Method for the determination of phosphorus in nickel ferronickel and nickel alloys by phosphovanadom.pdf

1、BRITISH STANDARD BS 6783-13: 1992 ISO 11400: 1992 Sampling and analysis of nickel, ferronickel and nickel alloys Part 13: Method for the determination of phosphorus in nickel, ferronickel and nickel alloys by phosphovanadomolybdate molecular absorption spectrometryBS6783-13:1992 This British Standar

2、d, having been prepared under the directionof the Non-ferrous Metals Standards Policy Committee, was published underthe authority of the Standards Board and comesintoeffect on 15December1992 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference NFM/10 Draf

3、t for comment 91/39171 DC ISBN 0 580 21416 8 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: Associatio

4、n of 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 D

5、evelopment 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 CommentsBS6783-13:1992 BSI 10-1999 i Contents Page Committees responsible Inside fr

6、ont 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 3 9 Test report 4 Table 1 Mass of sample to be taken 2 Table 2 Nominal composition of test samples 4 Table 3 Results of

7、 statistical analysis 4 List of references Inside back coverBS6783-13:1992 ii BSI 10-1999 National foreword This Part of BS 6783 has been prepared under the direction of the Non-ferrous Metals Standards Policy Committee. It is identical with ISO 11400:1992 Nickel, ferronickel and nickel alloys Deter

8、mination of phosphorus content Phosphovanadomolybdate molecular absorption spectrometric method published by the International Organization for Standardization (ISO). At present this British Standard consists of 13 Parts all concerned with analysis of nickel, ferronickel and nickel alloys. Further I

9、nternational 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 Standard. The Technical Committee has reviewed the provisions of ISO 648, to which normative reference is made in

10、the text, and has decided that they are acceptable for use in conjunction with this standard. ISO 648 is related to BS 1583:1986 Specification for one-mark pipettes. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible

11、for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding British Standard ISO 1042:1983 BS 1792:1982 Specification for one-mark volumetric flasks (Identical) ISO 5725:1986 BS 549

12、7 Precision of test methods Part 1:1987 Guide for the determination of repeatability and reproducibility for a standard test method by inter-laboratory tests (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 4, an inside back cover a

13、nd 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 the inside front cover.BS6783-13:1992 BSI 10-1999 1 1 Scope This International Standard specifies a molecular absorption spectrometric metho

14、d for the determination of the phosphorus content in nickel, ferronickel and nickel base alloys in the range of0,000 5 % (m/m) to 0,05 % (m/m). Arsenic, chromium, hafnium, niobium, silicon, tantalum, titanium and tungsten interfere, but the interferences can be avoided by complexation or volatilisat

15、ion (for Cr). The lowest phosphorus content 0,000 5 % (m/m) can only be reached in samples with low contents of the interfering elements. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At

16、the time of publication, the 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 IS

17、O maintain registers of currently valid International Standards. ISO 648:1977, Laboratory glassware One-mark pipettes. 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 metho

18、d by inter-laboratory tests. 3 Principle Dissolution of a test portion in a mixture of nitric and hydrochloric acids. Fuming with perchloric acid in a PFA or PTFE beaker and removal of chromium as volatile chromylchloride. Complexation of silicon and the refractory elements with fluoride ions. Conve

19、rsion of phosphorus to phosphovanadomolybdic acid in a perchloric and nitric acid solution. Extraction of phosphovanadomolybdic acid into 4-methyl-2-pentanone with citric acid present to complex arsenic. 4 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analyti

20、cal grade and only distilled water or water of equivalent purity. Verify by blank tests (7.6) that the relevant reagents are free from phosphorus. Lots giving high blank values are unsuitable and should not be used. The blank value should be below 0,000 5 % (m/m), calculated for 1 g of sample. 4.1 N

21、itric acid, 20= 1,41 g/ml, diluted 1 + 4. 4.2 Hydrofluoric acid, 40 % (m/m), 20= 1,14 g/ml. 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 see

22、k medical advice. 4.3 Citric acid, solution. Dissolve 500 g of citric acid monohydrate (H 8 C 6 O 7 .H 2 O) in water, dilute to 1 000 ml and mix. 4.4 4-methyl-2-pentanone (methyl isobutyl ketone). 4.5 Hexaammonium heptamolybdate, solution. Dissolve 15 g of hexaammonium heptamolybdate tetrahydrate (N

23、H 4 ) 6 Mo 7 O 24 .4H 2 O in water and dilute to 100 ml. Prepare a fresh solution each day. If high and unstable blank values appear, there might be a problem with the salt used. In such a case, switch to another lot. 4.6 Ammonium metavanadate, solution. Dissolve 2,5 g of ammonium metavanadate (NH 4

24、 VO 3 ) in water and dilute to 1 000 ml. 4.7 Sodium nitrite, solution. Dissolve 50 g of sodium nitrite (NaNO 2 ) in water and dilute to 1 000 ml. 4.8 Fluoro-boric acid, solution. Suspend 75 g of boric acid (H 3 BO 3 ) in 600 ml of hot water in a plastics beaker. Add 50 ml of hydrofluoric acid (4.2),

25、 dilute to 1 000 ml with water and digest until the boric acid dissolves. Keep the solution in a plastics bottle. The solution should be gently heated if the boric acid tends to crystallize. 4.9 Phosphorus, standard reference solution(1,000g/l). Weigh, to the nearest 0,000 1 g, 4,394 2 g of potassiu

26、m dihydrogenorthophosphate (KH 2 PO 4 ) previously dried to constant mass at 110 C and cooled in a desiccator. Transfer to a 1 000 ml one-mark volumetric flask and dissolve in water. Make up to the mark with water and mix. 4.10 Phosphorus, standard solution (10 mg/l). Transfer 10,0 ml of the phospho

27、rus standard reference solution (4.9) to a 1 000 ml one-mark volumetric flask. Make up to the mark with water and mix.BS6783-13:1992 2 BSI 10-1999 5 Apparatus Glassware shall be cleaned with hot hydrochloric acid ( 20= 1,18 g/ml) and rinsed with water. Ordinary laboratory apparatus and 5.1 Molecular

28、 absorption spectrometer, capable of measuring absorbance at a wavelength of 355 nm. 5.2 Heatable plastics beakers, made of polytetra-fluoroethylene (PTFE) or, preferably, of its perfluoroalkoxy copolymer (PFA). The PFA beakers have graphite bases and are specially constructed for fuming of acids up

29、 to 280 C. The beakers must be thoroughly cleaned before analysis. Fill the beakers with hydrochloric acid ( 20 = 1,18 g/ml) diluted 1 + 1, and boil for approximately 2 min. Rinse with water. 5.3 Heating source, with controllable surface temperature. 6 Sampling and sample preparation 6.1 Sampling an

30、d preparation of the laboratory sample shall be carried out by normal agreed procedures or, in the case of dispute, according to 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

31、If it is suspected that the laboratory sample is contaminated with oil or grease from the milling or drilling process, it shall be cleaned by washing with high purity acetone and dried in air. 6.4 If the laboratory sample contains particles or pieces of widely varying sizes, the test sample should b

32、e obtained by riffling. 7 Procedure WARNING Fuming perchloric acid is a powerful oxidant and can cause explosions when in contact with organic materials. All evaporations must be carried out in fume cupboards suitable for use with perchloric acid. 7.1 Test portion and preparation of test solution 7.

33、1.1 Weigh, to the nearest 0,1 mg, a test portion of the sample according to Table 1. 7.1.2 Transfer the test portion to the plastics beaker(5.2) and add 5 ml of nitric acid ( 20= 1,41 g/ml) and then 5 ml of hydrochloric acid ( 20= 1,18 g/ml). For samples with high contents of Nb, Si, Ta, or Hf, also

34、 add 7 ml of hydrofluoric acid(4.2). Fit the beaker with a PTFE cover and heat gently until the reaction ceases. Add 10 ml of perchloric acid ( 20= 1,66 g/ml) and, leaving a small opening to release the vapours, evaporate to dense perchloric acid fumes. NOTE 1Nickel and some copper-bearing nickel al

35、loys, such as monel, will dissolve more readily in nitric acid ( 20= 1,41 g/ml) diluted 1 + 1. 7.1.3 For samples containing less than 0,1 % (m/m) chromium, omit the next step (7.2) and proceed directly to 7.3. 7.2 Removal of chromium Continue fuming until no droplets are observed on the cover and al

36、l the chromium is oxidized to the hexavalent state. Start adding hydrochloric acid ( 20 = 1,18 g/ml) drop by drop to the fuming solution in the partly covered beaker, until coloured fumes are no longer liberated. Then resume fuming to reoxidize the remaining chromium. Repeat the treatment until no y

37、ellow fumes appear when the hydrochloric acid is added. Cool to room temperature. 7.3 Complexation 7.3.1 Add 25 ml of dilute nitric acid (4.1) and 4 ml of hydrofluoric acid (4.2) to the solution (7.2), and continue heating for 8 min to 10 min until all the precipitate is dissolved. NOTE 2It is impor

38、tant that the precipitated refractory oxides dissolve completely. If this does not happen, another 2 ml of hydrofluoric acid (4.2) may be added and the boiling repeated. If the precipitate still remains undissolved, a new test sample of lesser mass must be taken for analysis. 7.3.2 Add 10 ml of the

39、sodium nitrite solution (4.7) and continue to boil the solution for 10 min to reduce any residual dichromate and to expel all nitrous fumes. Wash the beaker walls a few times with water during boiling. Table 1 Mass of sample to be taken Expected phosphorus content Mass of sample Maximum concentratio

40、n of the interfering elements % (m/m) % (m/m) g As Hf Nb Ta Ti W 0,000 5 to 0,010 1,0 0,05 0,1 1 0,1 2 2 0,002 0 to 0,040 0,25 0,2 0,5 5 0,5 10 8 0,005 0 to 0,050 0,10 0,5 1,5 10 1 25 25BS6783-13:1992 BSI 10-1999 3 7.3.3 Add 40 ml of the fluoro-boric acid solution(4.8), rapidly cool the mixture to b

41、etween20 C and 30 C, and proceed immediately with the colour development. NOTE 3The oxides might precipitate again if it took more than10 min to cool the solution. 7.4 Colour development and extraction 7.4.1 Add 10 ml of the ammonium metavanadate solution (4.6) and 15 ml of the hexaammonium heptamol

42、ybdate solution (4.5) to the cooled clear solution. Allow to stand at a temperature between18 C and 25 C for a minimum of 7 min, but not longer than 15 min. 7.4.2 Transfer the solution to a 250 ml separating funnel which has been marked at 100 ml volume and, if necessary, make up to the mark with wa

43、ter. Add 10 ml of the citric acid solution (4.3), mix, and immediately follow with 40 ml of 4-methyl-2-pentanone (4.4). Shake the funnel for30 s. Allow the two layers to separate and discard the lower (aqueous) phase. Dry the inside of the stem of the separating funnel with a small piece of filter p

44、aper. Filter the organic layer through a dry paper into a small dry beaker. Proceed immediately with the spectrometric measurement. 7.5 Spectrometric measurement Ensure that the temperature of the solutions is constant to 1 C. Measure the absorbance of the solution with the molecular absorption spec

45、trometer (5.1) at a wavelength of 355 nm. Use 4-methyl-2-pentanone (4.4) as the reference, and cells with 1 cm optical path length. 7.6 Blank test Carry out a blank test in parallel with the determination, following the same procedure and using the same quantities of all the reagents as in the deter

46、mination, but omitting the test portion. 7.7 Calibration 7.7.1 Add 0 ml, 2,5 ml, 5,0 ml and 10,0 ml, respectively, of the phosphorus standard solution(4.10) to four plastics beakers (5.2). The additions correspond to 0 mg, 0,025 rag, 0,05 mg and0,100 mg of phosphorus. Proceed as directed in7.1.2 to

47、7.5. 7.7.2 Subtract the absorbance of the first “zero” solution from that of each solution containing phosphorus and plot the net absorbance against the mass, in milligrams, of phosphorus added. 7.8 Number of determinations Carry out the determination at least in duplicate. 8 Expression of results 8

48、.1 Calculation 8.1.1 Correct the absorbance reading of the test solution (see 7.5) by subtracting the absorbance reading in the blank test (7.6). Convert the net absorbance of the test solution into milligrams of phosphorus by means of the calibration graph (see7.7.2). 8.1.2 Calculate the percentage

49、 by mass of phosphorus in the test sample using the formula where 8.2 Precision 8.2.1 Laboratory tests Up to eight laboratories in six countries participated in the testing of this procedure using two nickel metal and four ferronickel samples (7 laboratories in 4 countries), and six nickel base alloys(8laboratories in 6 countries). The samples were analysed three or four times on different days. The nominal composition of the samples is given in Table 2. 8.2.2 Statistical analysis 8.2.2.1 Results from the interlaboratory