1、BRITISH STANDARD BS 6783-10: 1990 ISO 7528:1989 Sampling and analysis of nickel, ferronickel and nickel alloys Part 10: Method for determination of iron in nickel alloys (titrimetric method using potassium dichromate)BS6783-10:1990 This British Standard, having been prepared under the directionof th
2、e Non-ferrous Metals Standards Policy Committee, was published underthe authority of the BoardofBSI and comes into effect on 31 October 1990 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference NFM/10 Draft for comment 88/35913 DC ISBN 0 580 18960 0 Commi
3、ttees 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: British Non-ferrous Metals Federation British Steel Industr
4、y Engineering Equipment and Materials Users Association Ministry of Defence Nickel Development Institute Non-ferrous Metal Stockists Process Plant Association Stainless Steel Fabricators Association of Great Britain Coopted members Amendments issued since publication Amd. No. Date CommentsBS6783-10:
5、1990 BSI 10-1999 i Contents Page Committees responsible Inside front 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 Annex A (informative) Examples of co
6、mposition of some nickel alloys 5 Table 1 Mass of sample to be taken 2 Table 2 Nominal composition of test samples 3 Table 3 Results of statistical analysis 4 Table A.1 Examples of composition of some nickel alloys 5 Publication(s) referred to Inside back coverBS6783-10:1990 ii BSI 10-1999 National
7、foreword This Part of BS6783 has been prepared under the direction of the Non-ferrous Metals Standards Policy Committee. It is identical with ISO7528:1989 “Nickel alloys Determination of iron content Titrimetric method with potassium dichromate”, published by the International Organization for Stand
8、ardization (ISO). At present this British Standard consists of eleven 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 pu
9、blished as further Parts of this British Standard. The Technical Committee has reviewed the provisions of ISO385-1 and ISO648, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. ISO385-1 is related to BS846:1985 “Specification
10、for burettes” and ISO648 is related to BS1583:1986 “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 for their correct application. Compliance with a British Standard does not o
11、f 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 5497 Precision of test methods Part 1:1987 Guide for the determination of repea
12、tability 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 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may
13、 have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6783-10:1990 BSI 10-1999 1 1 Scope This International Standard specifies a titrimetric method for the determination of the iron content of nickel alloys in the range1% (m/m) to50% (m/m). This
14、 method is applicable only to alloys containing less than0,2% (m/m) of vanadium. Typical compositions of some nickel alloys are given in Annex A. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Stand
15、ard. At 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 IE
16、C and ISO maintain registers of currently valid International Standards. ISO 385-1:1984, Laboratory glassware Burettes Part 1: General requirements. ISO 648:1977, Laboratory glassware One-mark pipettes. ISO 1042:1983, Laboratory glassware One-mark volumetric flasks. ISO 5725:1986, Precision of test
17、methods Determination of repeatability and reproducibility for a standard test method by inter-laboratory tests. 3 Principle Dissolution of a test portion in a nitric/hydrochloric acid mixture and oxidation of chromium to chromium(VI) with perchloric acid. Precipitation of iron with ammonium hydroxi
18、de and dissolution of the precipitate in hydrochloric acid. Reprecipitation and dissolution of the iron. Reduction of the iron(III) with a slight excess of tin(II) chloride and oxidation of the excess with mercury(II) chloride. Addition of a sulfuric/phosphoric acid mixture and titration of the iron
19、(II) with potassium dichromate using diphenylamine sulfonate as the indicator. 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 Ammonium hydroxide, 20 =0,89g/ml. 4.2 Ammonium hydroxid
20、e, 20 =0,89g/ml, diluted1+2. 4.3 Hydrochloric acid, 20 =1,18g/ml. 4.4 Hydrochloric acid, 20 =1,18g/ml, diluted1+1. 4.5 Hydrochloric acid, 20 =1,18g/ml, diluted1+50. 4.6 Perchloric acid (HClO 4 ), 20 =1,66g/ml. 4.7 Ammonia, wash solution. Cautiously add20ml of ammonium hydroxide ( 20 =0,89g/ml) to1li
21、tre of warm water. Prepare this solution as required. 4.8 Tin(II) chloride, solution. Dissolve5g of tin(II) chloride dihydrate (SnCl 2 .2H 2 O) in10ml of hydrochloric acid ( 20 =1,18g/ml). Heat to boiling and dilute to100ml. Prepare this solution just before use. NOTEIt is possible to store this sol
22、ution in a brown glass bottle with the addition of granular or spongy tin metal. 4.9 Mercury(II) chloride, saturated solution. WARNING Mercury(II) chloride is very poisonous. Appropriate precautions shall therefore be taken in handling this chemical. Add60g to100g of mercury(II) chloride (HgCl 2 ) t
23、o400ml of hot water, shake, and cool to ambient temperature. More water may be added from time to time as long as crystals remain undissolved. 4.10 Nitric/hydrochloric acid, mixture. WARNING This acid mixture is highly corrosive and unstable. Noxious gas (chlorine) is liberated on standing. It shall
24、 be prepared and used in a fume cupboard and shall not be kept in a closed container. Carefully mix25ml of nitric acid ( 20 =1,41g/ml) and75ml of hydrochloric acid ( 20 =1,18g/ml). This mixture is not stable and shall be prepared just before use. 4.11 Sulfuric/phosphoric acid, mixture. Slowly, and w
25、ith constant stirring, add150ml of sulfuric acid (H 2 SO 4 , 20 =1,84g/ml) to500ml of water. Cool the solution and add150ml of phosphoric acid (H 3 PO 4 , 20 =1,83g/ml). Mix, cool and dilute to1litre. 4.12 Potassium dichromate, standard volumetric solution, c(1/6K 2 Cr 2 O 7 )=0,035mol/l. Dissolve e
26、xactly1,7161g of potassium dichromate (K 2 Cr 2 O 7 ,99,95% minimum purity) previously dried at105 C for1h, in500ml of water. Transfer to a1000ml one-mark volumetric flask, dilute to the mark with water and mix. 4.13 Sodium diphenylamine sulfonate, indicator solution. Dissolve0,20g of sodium dipheny
27、lamine sulfonate (C 6 H 5 NHC 6 H 4 SO 3 Na) in100ml of water. Store in a dark-coloured bottle.BS6783-10:1990 2 BSI 10-1999 5 Apparatus Ordinary laboratory apparatus and 5.1 Burette, of capacity50ml, graduated in0,1ml divisions, complying with the requirements of ISO385-1, class A. 5.2 One-mark pipe
28、ttes, complying with the requirements of ISO648, class A. 5.3 One-mark volumetric flasks, complying with the requirements of ISO1042, class A. 6 Sampling and sample preparation 6.1 Sampling and preparation of the laboratory sample shall be carried out by normal agreed procedures or, in case of dispu
29、te, by 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 oil or grease from the milling or drilling process, it
30、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 be obtained by riffling. 7 Procedure WARNING Fuming perchloric acid is a powerful oxidant and can cause an explosive mixtur
31、e when in contact with organic materials. All evaporations must be carried out in fume cupboards suitable for use with perchloric acid. 7.1 Preparation of the test solution 7.1.1 Weigh a test portion containing between10mg and60mg of iron according to Table 1 and transfer to a400ml or600ml tall-form
32、 beaker. Table 1 Mass of sample to be taken 7.1.2 Add25ml of the nitric/hydrochloric acid mixture (4.10) and heat until the sample is dissolved and nitrous fumes are removed. If the alloy resists dissolution, add the hydrochloric acid(4.3) in1ml increments and continue heating to dissolve the sample
33、. For some alloys, an acid mixture containing30ml of hydrochloric acid and2ml of nitric acid is more effective. NOTEIf the laboratory sample consists of large pieces, a1g test portion may be taken for iron levels higher than10% (m/m). The solution should be transferred to a250ml one-mark volumetric
34、flask and a test portion of50ml for10% (m/m) to25% (m/m) iron or25ml for25% (m/m) to50% (m/m) iron taken, using a pipette, and processed as in 7.1.3. 7.1.3 Add15ml of the perchloric acid (4.6) and evaporate to dense white fumes. Continue heating until the solution boils rapidly for1min to ensure tha
35、t the chromium is fully oxidized. Cool the solution, dilute to200ml with hot water, and add10ml of the hydrochloric acid (4.3) and stir. 7.1.4 Add the ammonium hydroxide (4.1) slowly until the precipitate formed slowly dissolves and the nickel ammine complex is completely formed. Add quickly a25ml e
36、xcess. Simmer the solution for2min to3min to allow the iron(III) hydroxide precipitate to coagulate. Add a further5ml of the ammonium hydroxide to maintain the alkalinity and then filter through a15cm paper of medium porosity. Rinse the beaker and wash the precipitate thoroughly with hot ammonia was
37、h solution (4.7). 7.1.5 Wash the precipitate from the filter paper into the original beaker with cold water. Dissolve any remaining particles from the filter paper with about25ml of hot hydrochloric acid diluted1+1(4.4), collecting the solution in the original beaker. Wash the filter paper thoroughl
38、y with the hydrochloric acid diluted1+50(4.5) Dissolve any particles of iron(III) hydroxide adhering to the sides of the beaker by drop by drop addition of the hydrochloric acid diluted1+1. Heat to complete dissolution of the precipitate. 7.1.6 Dilute the solution to200ml with hot water and reprecip
39、itate the iron(III) hydroxide by slowly adding the ammonium hydroxide diluted1+2until precipitation is complete. Add a25ml excess and simmer the solution for2min to3min to allow the iron precipitate to coagulate. 7.1.7 Add a further5ml of the ammonium hydroxide diluted1+2to maintain the alkalinity a
40、nd filter through a15cm medium porosity paper. Wash the beaker and the precipitate thoroughly with hot ammonia wash solution (4.7). Expected iron content Mass of sample Weighing accuracy % (m/m) g g 1 to 5 1,0 to 1,2 0,002 5 to 10 0,5 to 0,6 0,001 10 to 25 0,20 to 0,21 0,000 5 25 to 50 0,10 to 0,11
41、0,000 2BS6783-10:1990 BSI 10-1999 3 7.1.8 Wash the precipitate from the filter paper into the original beaker with water, redissolve any remaining particles from the filter paper with about25ml of hot hydrochloric acid diluted1+1(4.4), collecting the solution in the original beaker. Wash the filter
42、paper thoroughly with hydrochloric acid diluted1+50(4.5). Dissolve any particles of iron(III) hydroxide adhering to the sides of the beaker by drop by drop addition of hydrochloric acid diluted1+1. Heat to complete dissolution of the precipitate. 7.1.9 Evaporate the iron solution to approximately30m
43、l and sparingly wash the inside of the beaker with water. Heat the solution to boiling and cautiously add the tin(II) chloride solution (4.8) dropwise until the yellow colour of the iron(III) is just discharged, then add1or2drops more. Add200ml of cold water and cool quickly to room temperature. NOT
44、EThe volume of the hydrochloric acid, diluted1+1, should not exceed30ml for effective reduction of the iron(III) with tin(II) chloride. 7.2 Determination 7.2.1 Add10ml of the mercury(II) chloride solution(4.9) to the diluted solution from7.1.9, stir well and allow to stand for approximately5min. If
45、the iron has been properly reduced, a light silky precipitate of mercury(II) chloride should be evident within2min. If a black precipitate is obtained, too much tin(II) chloride has been added and the determination should be abandoned. 7.2.2 Add10ml of the sulfuric/phosphoric acid mixture (4.11) and
46、2or3drops of the sodium diphenylamine sulfonate indicator (4.13). 7.2.3 Titrate the iron with the potassium dichromate standard volumetric solution (4.12). As the end-point is approached, the colour deepens to a blue green which changes to a permanent purple or violet-blue on the addition of1more dr
47、op of the potassium dichromate solution. Note the volume of titrant. 7.3 Blank test Carry out a blank test in parallel with the determination, by the same procedure, using the same reagents as in the determination. NOTEIron(III) must be present in the solution to obtain the purple end-point. If the
48、colour fails to form, the blank is less than the equivalent of1drop of0,02mol/l iron(II) sulfate, as this contains sufficient iron to yield an end-point. 7.4 Number of determinations Carry out the determination at least in duplicate. 8 Expression of results 8.1 Method of calculation The iron content
49、, expressed as a percentage by mass, is given by the formula where V 0is the volume, in millilitres, of the potassium dichromate solution (4.12), used in the blank test; V 1is the volume, in millilitres, of the potassium dichromate solution, used in the determination; c is the actual concentration, expressed in moles of1/6K 2 Cr 2 O 7per litre, of the potassium dichromate solution (4.12); 0,05585is the mass, in grams, of iron corresponding to1,00ml of potassium dichromate solution, c(1/6 K 2 Cr 2 O 7 )=1,000mol/l; m is the mass,
