1、 DEUTSCHE NORM December 2005DIN 38409-7 ICS 13.060.50 Supersedes DIN 38409-7:2004-03 German standard methods for the examination of water, waste water and sludge Parameters characterizing effects and substances (group H) Part 7: Determination of acid and base-neutralizing capacities (H 7) Deutsche E
2、inheitsverfahren zur Wasser-, Abwasser- und Schlammuntersuchung Summarische Wirkungs- und Stoffkenngren (Gruppe H) Teil 7: Bestimmung der Sure- und Basekapazitt (H 7) Document comprises 24 pagesTranslation by DIN-Sprachendienst. In case of doubt, the German-language original should be consulted as t
3、he authoritative text. No part of this translation may be reproduced without prior permission of DIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, has the exclusive right of sale for German Standards (DIN-Normen). English price group 13 www.din.de www.beuth.d
4、e !,l(-“10.06 9730510DIN 38409-7:2005-12 2 Contents Page Foreword2 Introduction .4 1 Scope 4 2 Normative references 5 3 Terms and definitions .6 4 Determination of pH 8,2 and 4,3 acid-neutralizing capacities.7 5 Determination of pH 4,3 acid-neutralizing capacity 10 6 Determination of pH 4,3 base-neu
5、tralizing capacity . 12 7 Determination of pH 8,2 base-neutralizing capacity by direct titration without adding tartrate/citrate solution. 13 8 Determination of pH 8,2 base-neutralizing capacity by direct titration with tartrate/citrate solution added 16 9 Determination of pH 8,2 base-neutralizing c
6、apacity by back-titration 17 10 Results of interlaboratory testing . 20 Annex A (informative) Preparation and mode of action of tartrate/citrate masking solution 21 Annex B (informative) Explanatory notes 23 Foreword This standard has been prepared jointly with Wasserchemische Gesellschaft (Water Ch
7、emistry Society), a specialist group of the Gesellschaft Deutscher Chemiker (German Chemists Society) (see Annex B). Expert assistance and specialized laboratories will be required to perform the analyses specified in this standard. Existing safety instructions shall be observed. When using the stan
8、dard, a check shall be made on a case-by-case basis as to whether and to what extent additional boundary conditions have to be specified. DIN 38409 German standard methods for the examination of water, waste water and sludge Parameters characterizing effects and substances (group H) comprises furthe
9、r parts. Annex B gives a survey of the German standard methods groups A to T. Annexes A and B are informative. Amendments This standard differs from the May 1979 edition as follows: a) The methods of determining the pH 8,2 and pH 4,3 acid-neutralizing capacities of water whose pH value is greater th
10、an 8,2 have been combined (Method DIN 38409 H 7-1). b) Method DIN 38409 H 7-2 describes the determination of pH 4,3 acid-neutralizing capacity and can be used for water whose pH value is greater than 4,3. DIN 38409-7:2005-12 3 c) Method DIN 38409 H 7-3 supersedes method DIN 38409 H 7-2-1 Determinati
11、on of pH 4,3 base-neutralizing capacity (H 7). d) Method DIN 38409 H 7-4-1 supersedes method DIN 38409 H 7-2-2 Determination of pH value 8,2 base-neutralizing capacity (H 7). e) The following methods have been included: Method DIN 38409 H 7-4-2 Determination of pH 8,2 base-neutralizing capacity by d
12、irect titration with tartrate/citrate solution added; Method DIN 38409 H 7-4-3 Determination of pH 8,2 base-neutralizing capacity by back-titration. f) For all determinations involving a titration to end-point equivalent to a pH value of 8,2, the water samples are no longer transferred to titrating
13、vessels using pipettes, but directly to sampling vessels where they are titrated. Flat bottom bottles with solid stopper are now used for sampling. The preparation and the use of sodium hydroxide solution and 0,02 mol/l hydrochloric acid are no longer required. g) When determining the base capacity
14、to a pH value of 8,2 by direct titration, the use of tartrate/citrate masking solution for the complex formation of calcium and heavy-metal ions is confined to cases where interference occurs. h) The masking solution is no longer adjusted by dilution with deionized water, but is directly adjusted to
15、 the optimum pH value of 7,4 using an acid or a base, depending on the application intended. Annex A provides information on the preparation and the mode of action of the tartrate/citrate solution. This standard differs from the March 2004 edition as follows: a) Clause 1, third from last sentence in
16、 the German text: The word ist has been deleted. b) Subclause 4.7, last sentence: m1was incorrect and has been replaced by m2. c) Subclause 6.1, second line: The base capacity K is now indicated with the corresponding index B4,3. d) Subclause 8.8, key to equation (10): The sample volume V1was incorr
17、ect and has been replaced by V2. e) Subclause 9.8, equation (13): The denominator V2was incorrect and has been replaced by V3. Previous editions DIN 8103: 1936-11 DIN 19641: 1961-09 DIN 38409-7: 1979-05, 2004-03 DIN 38409-7:2005-12 4 Introduction The methods specified in this standard serve to deter
18、mine the buffering capacities of water by titrating to end-points at pH values 4,3 and 8,2. These values reflect the equilibrium of carbonic acid and its ions in water and are based on the points of inflection in the steep portions of the titration curve obtained when a 0,01 mol/l sodium carbonate s
19、olution is titrated with hydrochloric acid. At 25 C, an aqueous solution of carbon dioxide having a hydrogen carbonate ion concentration in mmol/l that is 1 % of that of dissolved carbon dioxide and an ionic strength of 10 mmol/l has a pH value of 4,3 and virtually contains only dissolved carbon dio
20、xide (CO2aq). At 25 C, an aqueous hydrogen carbonate solution containing more than 1 mmol/l hydrogen carbonate ions and having an ionic strength of 10 mmol/l has a pH of 8,2 and virtually contains only hydrogen carbonate ions. If the contributions of weak acids other than carbonic acid and weak base
21、s other than the anions of carbonic acid to the buffering capacity are negligible, titration to end-points at pH values of 4,3 and 8,2 provides an important basis for characterizing a water. It yields basic experimental water chemistry parameters for calculating the carbonic acid equilibria and the
22、calcite saturation of a water. Depending on the extent of the other analytical data available, calcite saturation data can be calculated by the method described in DIN 38404-10. If the amount-of-substance concentrations of sodium, potassium, calcium, magnesium, chloride, sulfate and nitrate ions are
23、 also known, the pH value of a water at a given temperature can be calculated by the method specified in clause 6 of DIN 38404-10:1995-04. Conversely, if the pH value is known, either of the associated buffering capacities can be calculated. This makes it possible to check the consistency of analyti
24、cal values (cf. 1 in clause 2 Normative references). CAUTION Users of this standard should be familiar with standard laboratory practice. It is not claimed that all the safety problems associated with the use of the standard have been dealt with exhaustively here. It is therefore the responsibility
25、of the user to take appropriate safety precautions and to ensure that these comply with national regulations. 1 Scope This standard specifies six methods of determining acid- and base-neutralizing capacity. Method H 7-1 in clause 4 serves to determine pH 8,2 and 4,3 acid-neutralizing capacities and
26、can be used for water whose pH value is greater than 8,2, a category that, in practice, includes mainly soft to medium-hard drinking water, ground water and surface water having acid-neutralizing capacities of less than 2 mmol/l. Method H 7-2 in clause 5 serves to determine pH 4,3 acid-neutralizing
27、capacity and can be used for water whose pH value is greater than 4,3. Method H 7-3 in clause 6 serves to determine pH 4,3 base-neutralizing capacity and can be used for water whose pH value is less than 4,3. Some naturally occurring drinking water, ground water or surface water that has been subjec
28、ted to an acidification process may fall into this category. Method H 7-4-1 in clause 7 serves to determine pH 8,2 base-neutralizing capacity without adding tartrate/citrate solution and can be used for water whose pH value is less than 8,2 and in which there is no interference due to precipitation
29、of heavy-metal hydroxides and carbonates or of calcium carbonate. Method H 7-4-2 in clause 8 serves to determine pH 8,2 base-neutralizing capacity with tartrate/citrate solution added and can be used for water whose pH value is less than 8,2 and in which there is interference due to precipitation of
30、 heavy-metal hydroxides and carbonates or of calcium carbonate, unless the amount of masking solution added is insufficient to prevent such precipitation, in which case the analytical procedure described in 2 should be used. DIN 38409-7:2005-12 5 Method H 7-4-3 in clause 9 serves to determine pH 8,2
31、 base-neutralizing capacity by back-titration and can be used for water whose pH value is less than 8,2. It is recommended for water with a carbon dioxide content in excess of 2 mmol/l, unless the amount of masking solution added is insufficient to prevent precipitation, in which case the analytical
32、 procedure described in 2 should be used. These are volumetric methods that do not require calibration and are based on sodium carbonate as primary standard. The commercially available acids and bases used have nominal amount-of-substance concentrations of 0,1 mol/l, 0,25 mol/l and 0,5 mol/l. Their
33、standardization with sodium carbonate does not therefore form part of the standard. The accuracy of the methods depends on the uncertainties relating to the amount-of-substance concentrations of the acids and bases used, the measurement of the volumes read off and taken for titration and the precisi
34、on of the end-point determinations. The decision, detection and determination limits cannot be determined by statistical methods. A guide to the lower limit of application may be provided by the acid- or base-neutralizing capacity indicated by the volume of base or acid added, which is ten times the
35、 repeatability error of the burette used. Depending on the type of sample, transportation and storage may bring about changes in the water quality of the sample. It is therefore essential to perform the analysis within 48 hours of sampling and to check for changes due to transport and storage. If ne
36、cessary, the procedure shall be modified to prevent such changes. 2 Normative references This standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the titles of the publications are l
37、isted below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to (including amendments) applies. DIN 12331, Bea
38、kers for laboratory use DIN 12691, Class AS fast delivery one-mark bulb pipettes, with a waiting time of 15 seconds, for laboratory use DIN 12700-1, Burettes for laboratory use General requirements DIN 19261, Terminology associated with pH measurement using galvanic cells DIN 19265, pH measurement A
39、dditional pH measuring apparatus Requirements DIN 19266, Standard buffer solutions for calibrating pH measuring equipment DIN 38404-10:1995-04, German standard methods for the examination of water, waste water and sludge Physical and physicochemical parameters (group C) Determination of calcite satu
40、ration of water (C 10) DIN EN ISO 4796-2, Laboratory glassware Bottles Part 2: Conical neck bottles (ISO 4796-2:2000) DIN EN ISO 8655-3, Piston-operated volumetric apparatus Part 3: Piston burettes (ISO 8655-3:2002) DIN ISO 1773, Laboratory glassware Narrow-necked boiling flasks (ISO 1773:1997) DIN
41、ISO 3696, Water for analytical laboratory use Specification and test methods (ISO 3696:1987) DIN 38409-7:2005-12 6 1 Eberle, S.H. and Donnert, D. Berechnung des pH-Wertes der Calcitsttigung eines Trinkwassers unter Bercksichtigung der Komplexbildung (Calculation of the pH value of the calcite satura
42、tion of a drinking water taking complex formation into consideration). Z. Wasser-Abwasser-Forsch., 1991: 24, 258-268. 2 Fresenius, W. and Quentin, K.-E. Untersuchung der Mineral- und Heilwsser, Bestimmung der Quellen-gase (Examination of mineral and spa water, determination of spring gases). In: Han
43、dbuch der Lebens-mittelchemie (Manual of Foodstuffs Chemistry), Vol. 8, Parts 1 and 2, Wasser und Luft (Water and air), Berlin, Heidelberg, New York: Springer-Verlag, 1970, 1020-1027. 3 Terms and definitions 3.1 buffering capacity the amount of hydrogen or hydroxide ions per unit volume of water, ex
44、pressed in mmol/l or mol/m3, required to adjust the pH to a given value 3.2 acid-neutralizing capacity1)the amount of hydrogen ions per unit volume of water, expressed in mmol/l or mol/m3, necessary to adjust the pH to a given value 3.3 pH 4,3 acid-neutralizing capacity, KA4,32)the amount of hydroge
45、n ions, expressed in mmol/l or mol/m3, necessary to adjust the pH to a value of 4,3 NOTE The pH 4,3 acid-neutralizing capacity is mainly a function of the concentration of hydrogen carbonate, carbonate and hydroxide ions, but other buffering substances, such as ammonia, borates, phosphates, silicate
46、s and anions of humic acids and other organic acids, are also included in the result of the analysis. If the water contains negligible amounts of other buffering substances, the pH 4,3 acid-neutralizing capacity can be calculated from the pH value and the pH 8,2 buffering capacity can be calculated
47、using computation method No. 3 described in DIN 38404-10 if the amount-of-substance concentrations of sodium, potassium, calcium, magnesium, chloride, sulfate and nitrate ions are known, bearing in mind the scope of clause 6 in DIN 38404-10:1995-04. 3.4 pH 8,2 acid-neutralizing capacity, KA8,23)the
48、amount of hydrogen ions per unit volume of water, expressed in mmol/l or mol/m3, necessary to adjust the pH to a value of 8,2 NOTE The pH 8,2 acid-neutralizing capacity is mainly a function of the concentration of carbonate and hydroxide ions, but other buffering substances, such as ammonia, borates
49、, phosphates and silicates, are also included in the result of the analysis. If the water contains negligible amounts of other buffering substances, the pH 8,2 acid-neutralizing capacity can be calculated from the pH value and the pH 4,3 acid-neutralizing capacity can be calculated using computation method No. 3 described in DIN 38404-10 if the amount-of-substance concentrations of sodium, potassium, calcium, magnesium, chloride, sulfate and nitrate ions are known, bearing in mind the scope of clause 6 in DIN 384
