BS EN 25813-1984 Water quality - Determination of dissolved oxygen - Iodometric method《水质 溶解氧的测定 碘滴定法》.pdf

1、m 1624669 0357552 5T2 BRITISH STANDARD Water quality - Determination of dissolved oxygen - Iodometric method The European Standard EN 25813 : 1992 has the status of a British Standard Quaiit de leau - Dosage de loxygne dissous - Mthode iodomtrique Wasserbeschaffenheit - Bestimmung des gelsten Sauers

2、toffs - Iodometrisches Verfahren UM: 628.1/.3 : 620.1 : 543.371 BS EN 26813 : 1993 BS6068: Section 2.3 : 1993 Is0 6813 : 1983 m lib24bb9 0357553 439 ExJRoPmsTANDARD NORME EUROPENNE EuROP;li;scHE NORM EN 25813 : 1992 October 1992 LJDC 62.il.3 : 620.1 : 543.371 Descriptors: Water, quality, water tests

3、, chemical analysis, determination of content, oxygen, iodometry English version Water quality - Determination of dissolved oxygen - Iodometsic method (is0 5813 : 1983) Qualitk de leau - Dosage de loxygne issous - Mthode iodomtrique (IS0 5813 : 1983) Wassehchaffenheit - Bestimmung des gelsten Sauels

4、toffs - Iodometrisches Verfahren (IS0 5813 : 1983) This European Standard was approved by CEN on 1992-10-05. CEN members are bound to comply with the CEN/CENELEC Internai Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any altera

5、tion. Up-to-date lists and bibiiographical 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, French, German). A version in any other language made by transla

6、tion under the responsibility of a CEN member into its own language and notied to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Gennany, Greece, Iceland, Ireland, Italy, Luxembourg, N

7、etherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Noniialisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1060 Brussels O 1992 Copyright reserved to CEN members - Ref. No. EN 25813

8、 : 1992 E - Page 2 EN 26813 : 1992 = 1624669 0357554 375 bore word This European Standard is the endorsement of Is0 5813. Endorsement of IS0 5813 was recommended by CENAechnical Committee 230 Water analysis under whose competence this European Standard will henceforth fail. This European Standard sh

9、all be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by April 1993, and conflicting national standards shall be withdrawn at the latest by April 1993. The Standard was approved and in accordance with the CEN/CENELEC Internai Regu

10、iations, the following countries are bound to implement this European . Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom. 1- = Lb24bb9 0357555 201 Contents National fo

11、reword Method 1. Scope and field of application 2. Reference 3. Principle 4. Reagents 5. Apparatus 6. Procedure Page -2 7. Expression of results 8. Reproducibility 9. Special cases 3 10. Test report 3 3 Annex 3 4 4 Modified procedure when suspended matter, capable of fixing or consuming iodine, is p

12、resent British Standards Institution Page 5 5 6 6 7 lb24669 0357556 148 - BS 6068 : Section 2.3 : 1984 National foreword This Section of this British Standard, which has been prepared under the direction of the Environment and Pollution Standards Committee. is identical with IS0 5813-1 983 Water qua

13、lity - Determination of dissolved oxygen - lodometric method. The international standard was prepared by subcommittee 2. Physical, chemical and biochemical methods, of Technical Committee 147, Water quality, of the International Organization for Standardization (ISO) as a result of discussion in whi

14、ch the UK participated. A - In 1992 the European Committee for Standardbation (CEN) accepted IS0 5813 : 1983 as European ?ada.rd _. EN 25813 : 1992. Asa cons-en-ofhplemnhg the Euroan-bndard this British-Standard is renumbered as ES EN 25813 and any reference to BS 6068 : Section 2.3 should be read a

15、s a reference to Bs EN 25813. This Britkh Standard is being published in a series of Parts subdivided into Sections that will generally correspond to particular international standards. Sections are being. or will be, published in Parts 1 to 6 which, together with Part O, are as follows. I Part O. I

16、ntroduction Part 2. Physical, chemical and biochemical methods Part 3. Radiological methods Part 5. Microbiological methods Part 5. Biological methods Part 6. Sampling I Part 1. Glossary i Terminology and conventions. The text of the international standacd has been approved as suitable for publicati

17、on as a j British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point

18、on the baseline as the decimal marker. Wherever the words International Standard appear, referring to this standard, they should be read as British Standard. Cross-reference. IS0 5814 (at present in preparation) which is referred to in clauses 1 and 2 is of an advisory nature and does not affect the

19、 validity of this standardTHwever it is intended that this international standard will be published as a Section of BS 6068 : Pan 2. Compliance with a British Standard does not of itseif confer immunity from legal obligstiont. It is current practice in British Standards for the symbol L to be used f

20、or litre rather than 1. . _- . = Lb24bbS 0357557 O4 BS 6068 : Section 2.3 : 1984 1 Scope and field of application This International Standard specifies an iodometric method for the determination of dissolved oxygen in water by the so-called “Winkler procedure“ modified in order to make allowance for

21、 certain interferences. The iodometric method is the reference method for the deter- mination of dissolved oxygen in water. It is applicable to all types of water having dissolved oxygen concentrations greater than 0.2 mg/l, up to double saturation of oxygen (approxi- mately 20 mg/ll, which are free

22、 from interfering substances. Readily oxidizable organic substances such as tannins, humic acid and lignins, interfere. Oxidizable sulphur compounds such as sulphides and thiourea also interfere, as do actively respiring systems which readily consume oxygen. In the presence of such substances, it is

23、 preferable to use the electrochemical probe method specified in IS0 5814. Nitrites up to a concentration of 15 mg/l do not intrfere with the determination because they are destroyed by the addition of sodium azide. If oxidizing or reducing substances are present, it is necessa these are described i

24、n clause 9. If suspended matter, capable of fixing or consuming iodine, is present, the method may be used with the modification described in the annex, but it is preferable to use the electro- chmical probe method. 2 Reference IS0 5814, Water 90a/ity - Determinetion of dissoEved oxygen - ectrochemi

25、cai probe method. 3 Principle Reaction of dissolved oxygen in the sample with freshly precipitated manganese( II) hydroxide formed by the addition of sodium or potassium hydroxide to manganese(II1 sulphate. Acidification, and oxidation of iodide by the higher valency manganese compound so formed, li

26、berating an equivalent 1) At present at the stage of draft. quantity of iodine. Determination of the quantity of iodine liberated by titration with sodium thiosulphate. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent pu

27、rity. 4.1 Sulphuric acid, solution.*) Cautiously add 500ml of concentrated sulphuric acid (e = 1.84 g/ml) to 500 ml water, stirring continuously. 4.2 Sulphuric acid, solution, d1/2 H2S04) = 2 mol/l. 4.3 Alkaline iodide-azide reagent. .- . WARNING - Sodium azide is an extremely strong poison. If nitr

28、ites are known to be absent, this reagent may be omitted. Dissolve 35 g of sodium hydroxide (NaOH) or 50 g of potassium hydroxide (KOHII and 30 g of potassium iodide (KI) or g of sodium iodide (NaIll in approximately 50 ml of water. Dissolve separately 1 g of sodium azide (NaN,) in a few millilitres

29、 of water. Mix the two solutions and dilute to 100 ml. Store the solution in a stoppered, brown glass flask. After dilution and acidification, this reagent should not show any colour in the presence of the indicator solution (4.7). 4.4 (or manganese sulphate monohydrate, 380 g/l solution). Alternati

30、vely, use manganese(ll) chloride tetrahydrate, 450 g/l solution. Manganese(ll1 sulphate anhydrous, 340 g/l solution Filter any solution which is not clear. 2) If the presence of trivalent iron is suspected, usa phosphoric acid H3P04), p = 1.70 ghl. - 3 - I BS 6068 : Section 2.3 : 1984 4.5 Potassium

31、iodate, d1/6 Klo3) = 10 mmol/l, standard solution. D 1624bb 0357558 TL0 D Dry a few grams of potassium iodate (KI031 at 180 OC. Weigh 3,567 f 0,oW g and dissolve in water. Dilute to 1 O00 ml. Withdraw 100ml and dilute with water to 1 O00 ml in a volumetric flask. 4.6 Sodium thiorulphate, standard vo

32、lumetric solution, dNa2S2%) = lOmmol/l. 4.6.1 Preparation Dissolve 2,5 g of sodium thiosulphate pentahydrate (Na2S added near the end of the titration, or another suitable indicator. 7 Expression of results The dissolved oxygen content, expressed in milligrams of oxygen per litre, is given by the fo

33、rmula 4 Vl where Mr is the relative molecular mass of oxygen (M, = 32) ; VI is the volurne, in millilitres, of the test sample or the ali- quot portion CVl = V, if all the contents of the flask were titrated) ; V2 is the volume, in millilitres, of sodium thiosulphate solution (4.6) used to titrate t

34、he contents of the flask or the aliquot portion ; c is the actual concentration, expressed in millimoles per litre, of the sodium thiosulphate solution (4.6); V, fi = - v, - V where Vo is the volume, in millilitres, of the flask (5.11, V is the sum of the volumes of the manganeseill) sulphate soluti

35、on (4.4) (1 mi) and the alkaline reagent (4.3) (2 mi). The flask may then be transported to the laboratory. Report the result to one decimal place. If protected from light, the sample may be stored for up to 24 h. 6.5 Liberation of iodine Ensure that the precipitate which has been formed has settled

36、 so that it is in the lower third of the flask. Add slowly 1,5 ml of the sulphuric acid solution (4.1) or the corresponding volume of the phosphoric acid solution (see the .T. 8 Reproducibility Replicate determinations, with 10 degrees of freedom, of dissolved oxygen in air-saturated water (range 8,

37、5 to 9 mgIl), carried out in four separate laboratories, gave within batch standard deviations between 0,03 and 0.05mg of dissolved oxygen per litre. 5 W Lb24bb - BS 6068 : Section 2.3 : 1984 9 Special cases 9.1 Presence of oxidizing substances 9.1.1 Principle Determination, by titration on a second

38、 test sample, of the con- tent of oxidizing substances other than dissolved oxygen. Cor- rection of the result obtained in clause 7. 9.1.2 Procedure 9.1.2.1 Collect two test samples as specified in 6.3. 9.1.2.2 Carry out the determination of dissolved oxygen on the first test sample following the pr

39、ocedure specified in 6.4, 6.5 and 6.6. 9.1.2.3 Transfer quantitatively the second test sample to a conical flask of suitable size. Add 1,5 ml of the sulphuric acid solution (4.1) or the corresponding volume of the phosphoric acid solution (see the note to 4.111, then 2 ml of the alkaline reagent (4.

40、31 and 1 ml of the manganese(l1) sulphate solution (4.4). Leave for 5 min. Tiiate with the sodium thosulphate solution (4.6), using either the starch solution (4.71, added near the end of the titration, or another suitable indicator. 9.1.3 Expression of resuks The dissolved oxygen content, expressed

41、 in milligrams of oxygen per litre, is given by the formula MrV2c/, MrV4c 4 Vl 4 v3 - where M, VI, V2, c and fi have the same meanings as in clause 7 ; V3 is the volume, in millilitres, of the flask containing the second test sample; V4 is the volume, in millilitres, of sodium thiosulphate solution

42、(4.6) used to titrate the second test sample. 9.2 Presence of reducing substances 9.2.1 Principle Oxidation of the reducing substances in the first and second test samples by addition of an excess of sodium hypochlorite solution. Determination of the dissolved oxygen content of one of the test sampl

43、es. Determination of the excess of sodium hypochlorite in the other test sample. 0357560 679 W 9.2.2 Reagents The reagents specified in clause 4, and . 9.2.2.1 Sodium hypochlorite, solution containing approxi- mately 4 g of free chlorine per litre, obtained by dilution of a commercial concentrated s

44、odium hypochlorite solution, the concentration of which has been determined by iodometry. 9.2.3 Procedure 9.2.3.1 Collect two test samples as specified in 6.3. 9.2.3.2 Add to both test samples 1,oO ml (or, if necessary, a larger, accurately measured volume) of the sodium hypochlorite solution (9.2.2

45、.1) (see footnote to 6.2). Stopper the flasks and mix. Proceedson one test sample as specified in 6.4,6.5 and 6.6 and on thk other as specified in 9.1.2.3. 9.2.4 Expression of results The dissolved oxygen content, expressed in milligrams of oxygen per litre, is given by the formula Mr V2cf2 M, V4c -

46、 4 v, 4v3 - V5) where Mr , Vl, V2 and c have the same meanings as in clause 7; V3 and V4 have the same meanings as in 9.1.3; V5 is the volume, in millilitres, of sodium hypochlorite solution added to the test sample (usually V5 = 1,OO ml); VO v, - v, - V A = where V has the same meaning as in clause

47、 7, Vo is the volume, in millilitres, of the flask containing the first test sample. 10 Test report The test report shall contain the following information : a) a precise identification of the sample; b) the reference of the method used; c) the results, and the method of expression used; d) the ambi

48、ent temperature and atmospheric pressure ; e) any special details which may have been noted during the determination; f) details of any operations not specified in this Inter- national Standard or regarded as optional. 6 m Lb24669 0357563 505 Annex BS 6068 : Section 2.3 : 1984 Modified procedure whe

49、n suspended matter, capable of fixing or consuming iodine, is present) A.l Principle Flocculation of the suspended matter and separation by en- trainment with aluminium hydroxide. A.2 Reagents The reagents specified in clause 4, and A.2.1 Aluminium potassium sulphate dodecahydrate AIK(SO V“ is the sum of the volumes of aluminium sulphate solu- tion (A.2.1) (20 mll and ammonia solution A.2.2) (4 ml). Bibliography i11 MONTGOMERY, H.A.C., THOM, N.S., and COCKBURN, A. Determination of dissolved oxygen by the Winkler me