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1、BRITISH STANDARD BS 7755-3.2: 1995 ISO 10390: 1994 Soil quality Part 3: Chemical methods Section 3.2 Determination of pH Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:32:20 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7755-3.2:1995 This British Standard, h
2、aving been prepared under the direction of the Health and Environment Sector Board, was published under the authority of the Standards Board and comes into effect on 15 February 1995 BSI 03-1999 The following BSI references relate to the work on this standard: Committee reference EPC/48 Draft for co
3、mment 92/52700 DC ISBN 0 580 23567 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Health and Environment Sector Board to Technical Committee EPC/48, upon which the following bodies were represented: Association of Consulting Scientist
4、s Association of County Councils Association of Environmental Consultants Association of Public Analysts British Gas plc British Geological Survey British Society of Soil Science Chemical Industries Association Department of Agriculture Northern Ireland Department of the Environment Department of th
5、e Environment (Drinking Water Inspectorate) Department of Trade and Industry (Laboratory of the Government Chemist) Institute of Groundsmanship Institute of Terrestrial Ecology Institution of Environmental Health Officers Institution of Water and Environmental Management Macaulay Land Use Research I
6、nstitute Ministry of Agriculture, Fisheries and Food Soil Survey and Land Research Centre Water Research Centre Water Services Association of England and Wales The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Ceramic Research Ltd.
7、Institute of Occupational Medicine National Rivers Authority Royal Society of Chemistry Society of Chemical Industry Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:32:20 GMT+00:00 2006, Uncontrolled Co
8、py, (c) BSI BS 7755-3.2:1995 BSI 03-1999i Contents Page Committees responsibleInside front cover National foreword ii 1Scope1 2Normative references1 3Principle1 4Reagents1 5Apparatus2 6Laboratory sample2 7Procedure2 8Repeatability and reproducibility2 9Test report3 Annex A (informative) Results of a
9、n interlaboratory trial for the determination of the pH of soils4 Table 1 Repeatability2 Table A.1 The results of the interlaboratory trial for the determination of the pH-H2O4 Table A.2 The results of the interlaboratory trial for the determination of the pH-KCl4 Table A.3 The results of the interl
10、aboratory trial for the determination of the pH-CaCl24 List of referencesInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:32:20 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7755-3.2:1995 ii BSI 03-1999 National foreword This Section of BS 77
11、55 has been prepared under the direction of the Health and Environment Sector Board. It is identical with ISO 10390:1994 Soil quality Determination of pH, published by the International Organization for Standardization (ISO) ISO 10390 was prepared by Subcommittee 3, Chemical methods, of Technical Co
12、mmittee 190, Soil quality, with the active participation and approval of the UK. BS 7755 is being published in a series of Parts subdivided into Sections and Subsections that will generally correspond to particular international standards. Other Parts of BS 7755 are, or will be, as follows: Part 1:
13、Terminology and classification; Part 2: Sampling; Part 3: Chemical methods; Part 4: Biological methods; Part 5: Physical methods. The Technical Committee has reviewed the provisions of the draft of ISO 11464, to which normative reference is made in the text, and has decided that they are acceptable
14、for use in conjunction with this standard. When ISO 11464 is published, it is intended to implement it as a British Standard. Textual error. When adopting the text of the international standard, the textual error given below was discovered. It has been marked in the text and has been reported to ISO
15、 with a proposal to amend the text of the international standard. In 5.3, note 6, line 1, “In soil systems” should read “In soil suspensions”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct appli
16、cation. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International standardCorresponding British Standard ISO 1770:1981BS 1704:1985 Specification for solid-stem general purpose thermometers (Identical) ISO 3696:1987BS 3978:1987 Specif
17、ication for water for laboratory use (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will
18、 be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:32:20 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 10390:1994(E) BSI 03-19991 1 Scope This International Standard specifies an instrumental metho
19、d for the routine determination of pH using a glass electrode in a 1 : 5 (V/V) suspension of soil in water (pH-H2O), in a solution of 1 mol/l potassium chloride (pH-KCl) or in a solution of 0,01 mol/l calcium chloride (pH-CaCl2). This International Standard is applicable to all types of air-dried so
20、il samples, for example pretreated according to ISO 11464. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are s
21、ubject 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 ISO maintain registers of currently valid International Standards. ISO 1770:1981,
22、 Solid-stem general purpose thermometers. ISO 3696:1987, Water for analytical laboratory use Specification and test methods. ISO 11464:1), Soil quality Pretreatment of samples for physico-chemical analyses. 3 Principle A suspension of soil is made up in five times its volume of one of the following:
23、 water; a 1 mol/l solution of potassium chloride (KCl) in water; a 0,01 mol/l solution of calcium chloride (CaCl2) in water. The pH of the suspension is measured using a pH-meter. NOTE 1To make the procedure generally applicable to all types of soil samples, a V/V shaking ratio is chosen because the
24、n all soils can be treated in the same way. If a m/V ratio were chosen, the weighed amount of test sample would have to be adapted for soils with a low density, to enable the preparation of the suspension. For the purpose of this International Standard, taking the required volume of test portion wit
25、h a measuring spoon is sufficiently accurate. 4 Reagents Use only reagents of recognized analytical grade. 4.1 Water, with a specific conductivity not higher than 0,2 mS/m at 25 C and a pH greater than 5,6 (grade 2 water according to ISO 3696). 4.2 Potassium chloride solution, c(KCl) = 1 mol/l. Diss
26、olve 74,5 g of potassium chloride in water (4.1) and dilute to 1 000 ml at 20 C. 4.3 Calcium chloride solution, c(CaCl2) = 0,01 mol/l. Dissolve 1,47 g of calcium chloride dihydrate (CaCl2.2H2O) in water (4.1) and dilute to 1 000 ml at 20 C. 4.4 Solutions for the calibration of the pH-meter. Use at l
27、east two of the following calibration solutions. 4.4.1 Buffer solution, pH 4,00 at 20 C. Dissolve 10,21 g of potassium hydrogen phthalate (C8H5O4K) in water (4.1) and dilute to 1 000 ml at 20 C. The potassium hydrogen phthalate shall be dried before use for 2 h at 110 C to 120 C. 4.4.2 Buffer soluti
28、on, pH 7,00 at 20 C. Dissolve 3,800 g of potassium dihydrogen phosphate (KH2PO4) and 3,415 g of disodium hydrogen phosphate (Na2HPO4) in water (4.1) and dilute to 1 000 ml at 20 C. Potassium dihydrogen phosphate shall be dried before use for 2 h at 110 C to 120 C. 4.4.3 Buffer solution, pH 9,22 at 2
29、0 C. Dissolve 3,80 g of disodium tetraborate decahydrate (Na2B4O7.10H2O) in water (4.1) and dilute to 1 000 ml at 20 C. NOTE 2Disodium tetraborate may lose water of crystallization when stored for a long time. NOTE 3The buffer solutions 4.4.1, 4.4.2 and 4.4.3 are stable for one month if stored in po
30、lyethylene bottles. NOTE 4Buffer solutions that are commercially available may also be used. 1) To be published. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:32:20 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 10390:1994(E) 2 BSI 03-1999 5 Apparatus 5.1 S
31、haking or mixing machine. 5.2 pH-meter, with slope adjustment and temperature control 5.3 Glass electrode and a reference electrode, or a combined electrode of equivalent performance. NOTE 5In the case of pH-values greater than 10, an electrode specifically designed for that range should be used. NO
32、TE 6In2) soil systems, the danger of deterioration of performance, caused by breakage or contamination of the electrodes, is increased. 5.4 Thermometer, capable of measuring to the nearest 1 C, complying with type C according to ISO 1770. 5.5 Sample bottle, of capacity at least 50 ml, made of borosi
33、licate glass or polyethylene with a tightly fitting cap or stopper. 5.6 Spoon, of known capacity at least 5,0 ml. 6 Laboratory sample Use the fraction of particles of air-dried soil samples, or soil samples dried at a temperature not higher than 40 C, which passes through a square hole sieve with a
34、2 mm aperture. For example, soil samples pretreated according to ISO 11464 can be used. NOTE 7Drying may influence the pH of the soil. In some soil samples, particularly those containing sulfides, drying can lower the pH substantially. 7 Procedure 7.1 Preparation of the suspension 7.1.1 Take a repre
35、sentative test portion of at least 5 ml from the laboratory sample using the spoon (5.6). 7.1.2 Place the test portion in the sample bottle (5.5) and add five times its volume of water (4.1), potassium chloride solution (4.2) or calcium chloride solution (4.3). 7.1.3 Shake or mix the suspension vigo
36、rously, for 5 min, using the mechanical shaker or mixer (5.1), and wait at least 2 h, but not longer than 24 h. NOTE 8In most soils, equilibrium is reached within 2 h. When this is the case, measurements can be made after 2 h. NOTE 9In some contaminated soils, recently limed soils or carbonate-conta
37、ining soils, the equilibrium pH may not be reached within the time specified in 7.1.3. Consequently, values which are too low or too high, compared to naturally achieved equilibrium situations, will be obtained due to slow changes in the buffering system. To check whether this is the case, pH-measur
38、ements should be made according to this International Standard at least two different times between 2 h and 24 h of shaking. In this case, two or more pH-values should be reported to indicate the approximate pH of the soil, and the fact that the measurement is not stable should be reported in item e
39、) of the test report. 7.2 Calibration of the pH-meter Calibrate the pH-meter as prescribed in the manufacturers manual, using the buffer solutions given in 4.4. NOTE 10Using electrodes that are in good condition, equilibrium is normally reached within 30 s. 7.3 Measurement of the pH Adjust the pH-me
40、ter as indicated in the manufacturers manual. Measure the temperature of the suspension and take care that the temperature of the buffer solution and the soil suspension do not differ by more than 1 C. Shake the suspension thoroughly just before measurement of the pH. Measure the pH in the settling
41、suspension. Read the pH after stabilization is reached. Note the recorded values to two decimal places. NOTE 11If a swinging needle pH-meter is used, the second decimal place should be estimated. NOTE 12The reading may be considered stable when the pH measured over a period of 5 s varies by not more
42、 than 0,02 pH-unit. The time required for stabilization is usually 1 min or less, but may depend on a number of factors including the value of the pH (at high pH-values, it is more difficult to reach stabilization); the quality of the glass electrode (differences of manufacture between electrodes) a
43、nd its age; the medium in which the pH is measured (stabilization is reached more quickly in a KCl or CaCl2 medium than in water); the differences in pH between samples in a series; mechanical mixing before the measurement is performed which may help to achieve stable readings in a shorter time. NOT
44、E 13In samples with a high content of organic material (peat soils, pot soils, etc.) the suspension effect can play a role. For calcareous soils, it is possible that carbon dioxide is absorbed by the suspension. Under these circumstances, it is difficult to reach an equilibrium pH-value. 8 Repeatabi
45、lity and reproducibility The repeatability of the pH-measurement in two separately prepared suspensions shall satisfy the following demands: Table 1 Repeatability A summary of the results of an interlaboratory trial for the determination of the pH of soils is given in Annex A. 2) See national forewo
46、rd for details of textual error. pH-rangeAcceptable variation pH 8,00 0,15 0,20 0,30 0,40 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:32:20 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 10390:1994(E) BSI 03-19993 9 Test report The test report shall inclu
47、de the following information: a) a reference to this International Standard; b) all information necessary for complete identification of the sample; c) the aqueous medium used to make the suspension: whether the pH-H2O, pH-KCl or pH-CaCl2 has been determined; d) the results of the determinations to
48、the nearest 0,1 pH-unit; e) any difficulties experienced in establishing equilibrium conditions; f) details of any operations not specified in this International Standard or regarded as optional, as well as any factor which may have affected the results. Licensed Copy: London South Bank University,
49、London South Bank University, Fri Dec 08 10:32:20 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 10390:1994(E) 4 BSI 03-1999 Annex A (informative) The results of an interlaboratory trial for the determination of the pH of soils An interlaboratory trial was organized in 1990 by the Wageningen Agricultural University, to test the procedures specified in this International Standard. For this interlaboratory trial, the determination of the pH of five soils was carried out by 30 laboratories. The summary of the results