1、 CIEN Page 3 EN 24-94? : 11931 4.1a Wium nitrti3.2 FCeduaion of chromium arrdi vamedium The testi samples u Bestimmung des Vanadium-Gehalts; potentiometrisches Titrierverfahren (IS0 4947 : 1986) European Standard EN 24 947 : 1991 has the status of a DIN Standard. A comma is used as the decimal marke
2、r. National foreword This standard has been prepared by ECISS/TC 20. The responsible German body involved in the preparation of this standard was the NormenausschuB Eisen undStahl (Steel and iron Standards Committee). Standard referred to See Reference. EN comprises 8 pages. euth Veriag GmbH. Berlin
3、. has the exclusive right of sale for German Standards (DIN-Nomen). 04.93 DIN EN 24 947 Engl. Price group 7 Sales No. 1107 EUROPEAN STANDARD NORME EUROPENNE EUROP determination de la teneur en vanadium; mthode de titration potentiometrique (IS0 4947 : 1986) Stahl und Gueisen; Bestimmung des Vanadium
4、-Gehalts; potentiometrisches Titrierverfahren (IS0 4947 : 1986) This European Standard was approved by CEN on 1991-01-30 and is identical to the IS0 Standard as referred to. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this Europe
5、an Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English,
6、French, German). Aversion in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officiai versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland
7、, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Bruss
8、els 0 1991. Copyright reserved to all CEN members. Ref. No. EN 24 947 : 1991 E Page 2 EN 24 947 : 1990 Foreword On the proposal of Technical Committee TC 20, the Coordinating Commission (COCOR) of the European Committee for Iron and Steel Standardization (ECISS) decided in January 1991 to submit Int
9、ernational Standard IS0 4947 : 1986 Steel and cast iron - Determination of vanadium content -Potentiometric titration method to Formal Vote. This European Standard was approved by CEN on 1991 -01 -30. In accordance with the CENKENELEC Internal Regulations, the following countries are bound to implem
10、ent this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Endorsement notice The text of International Standard IS0 4947 : 1986 was approved by CEN as a E
11、uropean Standard without any modification. Page 3 EN 24 947 : 1991 1 Scope and fid of application This hitemational Standard cpecifias a potentiometric titration method for the detemination of vanadium in steei and cast iron. The method is applicable to vanadium contents between 0,04 and 2 % irn/mi.
12、 2 Reference SO377. Wrought steel - Selection and preparation of samples and test pieces. 3 Principle Dilution of a test portion with appropriate acids. Addition of hydrofluoric acid to keep tungsten in solution. Oxidation of chromium and vanadium by potassium peroxy- disulfate. Partial oxidation of
13、 chromium. While checking the potential of the solution, - reduction of chromium(V1) and vanadiumfV) by am- monium ironW sulfate; - oxidation of vanadium by slight excess of potassium per- manganate; reduction of the excess permanganate by sodium nitrite, and reduction of the excess sodium nitrite b
14、y sulfamic acid. Potentiometric titration of vanadium by ammonium iron(ll) sulfate standard solution. 4 Reagents . During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity, free from reducing or oxidizing ac
15、tivity. 4.1 4.2 4.3 Potassium peroxydisulfate (K mg K the mass, in miHigram, of the weighed potashm dichromate; V is the volume, in millilitres, of the ammonium iron(ll) sulfate standard solution (4.13) used for titration; O,25 is the ratio between the volume taken and the total volume of the potass
16、ium dichromate standard reference solution; 49,03 is the relative molecular mass of potassium dichromate divided by 6; 5034 is the relative atomic mass of vanadium. Apparatus Ordinary laboratory apparatus and 5.1 Potentiometric titration device which permits a dif- ference in potential to be measure
17、d with platinumfsaturated calomel electrodes. 6 Sampling Carry out sampling in accordance with IS0 377 or appropriate nation 7.3.1 Preparation of the test solution 7.3.1.1 Samples soluble in sulfuric acid Introduce the test portion (7.1 1 into a 400 ml beaker (see notes 7 and 2) and add 40 ml of sul
18、furic acid (4.5) for a 1 g or 2 g test portion. For a 5 g test portion, add 70 ml of sulfuric acid (4.5). Cover the beaker with a watchglass and heat gently until effervescence ceases. For samples with high silicon contents, add 5 to 70 drops of hydrofluoric acid (4.4). Bring to the boil to ensure c
19、omplete cessation of effervescence. If the test portion contains tungsten, add a sufficient quantity of hydrofluoric acid (4.4) to keep it in solution. In general 5 ml of hydrofluoric acid (4.4) will suffice for a 1 g test portion, 7 ml for a 2 g test portion, and 13 ml for a 5 g test portion. Dilut
20、e the solution to between 90 and 100 ml with water and proceed as in 7.3.2. NOTES 1 If hydrofluoric acid (4.4) is used, a fused silica beaker nd a fused silica watchglass shall be employed. 2 The glassware used should not contain more than O, however, this will not adversely affect the determination
21、. 7.3.1.2 Samples not readily duble in sulfuric acid For test portions difficult to dissolve in the sulfuric acid medium the initial dissolution may be accomplished with a mixture of nitric acid (4.3) and hydrochloric acid (4.2). After dissolution, add the quantity of sulfuric acid (4.5) already ind
22、icated in 7.3.1.1 and heat until white fumes are given off. Take up again with water, heating to dissolve the salts, then repeat the evaporation to white fumes to ensure that the nitric acid is completely eliminated. If the test portion contains tungsten,.add a sufficient quantity of hydrofluoric ac
23、id (4.4) to keep it in solution. In general 5 ml of hydrofluoric acid (4.4) will suffice for a 1 g test portion, 7 ml for a 2 g test portion, and 13 ml for a 5 g test portion. Page 5 EN 24 947 : 1991 Eliminate the excess potassium permanganate by adding sodium nitrite solution (4.101, drop by drop.
24、The potential will drop; when it reaches 850 mV, add a further 15 drops of this solution. Dilute the solution to between 90 and 100 ml with water and proceed as in 7.3.2. 7.32 Oxidation of chromium and vanadium When the potential is stabilized at about 770 mV, wait approxi- mately 30 s and add 5 ml
25、of sufamic acid solution (4.171. The potential will drop to about 740 mV and then increase again to about 800 mV. Then add 20 ml of orthophosphoric acid (4.7) if the volume is at or below 200 ml. If the volume is above 200 ml, add 30 to 40 ml of orthophosphoric acid (4.7). Wait for the potential to
26、stabilize (approximately 2 to 5 min). Cool the solution (7.3.11 to approximately 50 OC. Add 3 g of potassium pexoxydisutfate (4.1) per gram of test portion, heat slowly to boiling and boil for at least 10 min. 7.3.3 Preperation of the solution for measurement 7.4 Titration 7.3.3.1 Control of the oxi
27、dation of chromium and vanadium Cool the solution (7.3.2) to room temperature. If it is necessary to remove graphite. filter the solution through a cellulose pulp lined coarse filter paper and wash with sutfuric acid (4.6). adding several drops of hydrofluoric acid 14.4) to facilitate filter- ing. M
28、ake up the final volume of the solution to approximately 150 ml. When the potential is stable, titrate the vanadium with the am- monium ironill) sulfate standard solution (4.13) until the equi- valence point is reached. The potential at th point S between 5O and 670 mV. 8 Expression of results Intro
29、duce the electrodes of the potentiometric device (5.1) into the beaker and.agitate the solution, preferably with an electro- magnetic stirrer. The potential should be above 770 mV. 8.1 Method of calculation The vanadium (VI content, as a percentage by masc. is calculated from the fdbwing formula : I
30、f the potential is lower, or if it fails regularly, remove the elec- trodes from the solution, and repeat the operations of 7.3.2. Cool to room temperature and make up the volume to approxi- mately 150 ml. where Verify that the potential is above 770 mV. V, is the volume, in millilihes, of the ammon
31、ium iron(ll) sulfate standard solution (4.131 used for titrating the blank solution; 7.3.3.2 Reduction of chromium and vanadium Introduce the electrodes into the beaker and reduce chromium(Vl1 and vanadium(/) by adding ammonium iron(ll) sulfate solution (4.8) (see note) to a slight excess (the poten
32、tial drops to between 500 and !%O mV), agitating continuously at a constant speed. V, is the volume, in millilitres, of the ammonium iron(ll1 sulfate standard sdution (4.13) used for titrating the test solution: c is the corresponding concentration of the ammonium iron(lll sulfate standard solution
33、(4.131, expressed in milli- gram of vanadium per millilitre; m is the mass, in grams, of the test portion. NOTE - When the quantity of chromium is large (test portion of 5 g, or high chromium content) it is necessary to use a more concentrated ammonium ironill) sulfate solution (e.g. 400 g/l) at the
34、 start. then finish with the solution 4.8. 8.2 Precision 7.3.4 Oxidation of vanadium A planned trial of this method was carried out by twelve laboratories, at seven levels of vanadium, each laboratory mak- ing three determinations of vanadium at each level. The test samples used are listed in annex
35、A. The results obtained were treated statistically in accordance with IS0 5725, Precision of test methods - Determination of repeatability and reproducibility by inter-laboratory tests. Cool the solution (7.3.3) to a temperature below 15 OC to avoid partial oxidation of the chromium. Wait 2 min. The
36、n add, drop by drop, potassium permanganate solution (4.9) until the potential of the indicator electrode stabilizes between 1 100 and 1 160 mV (see note). The poten- tial shall not exceed this range in order to avoid partial oxidation of the chromium. NOTE - When the solution is not highly coloured
37、, oxidation with the permanganate can be obsetved (light pink colouring, stable for 2 min). The data obtained showed a logarithmic relationship between vanadium content and repeatabif (r) and reproducibility R 1 of the test results, as summarized in table 1. The graphic presentation of the fwres is
38、given in annex B. Wait 2 to 3 min, during which time the potential shall neither in- crease by more than 30 mV nor drop below 1 100 mV. Page 6 RepwtaMlhy 0,003 6 0,m 1 0.009 2 0,015 6 0,023 4 0,- 1 r EN 24 947 : 1991 Table 1 Rsproducibii R 0.005 2 0,009 o 0,013 7 0.m 7 0.m o 0,H 6 Levei of vanadium
39、% irn/mi 9 Testreport The test report shaH include the following particulars: a) the method used, by reference to this International Standard; b) the resub, and the form in which they are expressed; c) any unusual features noted during the determination: d) any operetion not specified in this Intern
40、ational Stan- dard, or any optional operation which may have influenced thenrsu(ts. Page 7 EN 24 947 : 1991 Annex A Additional information on the international Co-operative tests (Not an integral part of thk Intemational Standard.) Tabie 1 was derived from rhe resuits of the i- I ariaiyticai trials
41、by the workiog group 8 (convener: JAPAN) carried out in 1963 on six steel sampiesand one pig iron cample in three countries invoking tweive laoratories. The results of the triais were reported in document 17/1 N 579, December 1963. mc pmmtath of the precision data is siven in annex B. The test sampi
42、es used were as listed in table 2. la ble 2 Vanadium contemt Sample JSS la-3 (pig iron) JSS 600-7 boi steel) EURO 278-1 (high chromium steel) JSS 152-7 (low alloy steel) JSS 602-7 (td st&) JSS a7 (tool steel) JSS 609-7 (tool steel) Page 8 EN 24 947 : 1991 0,005 0,002 Annex B - - - - - - - I I I IlIll I I I I I I III I Graphic presentation of precision data (Not an integrai part of this . Standard. 1 figure - Relationship between vanadium content and repeatability ror reproducibility R
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