1、BRITISH STANDARD BS 7755-3.4: 1995 ISO 11265: 1994 Incorporating Amendment No. 1 to BS 7755-3.4 (Technical corrigendum 1 to ISO11265) Soil quality Part 3: Chemical methods Section 3.4 Determination of the specific electrical conductivity ICS 13.080BS7755-3.4:1995 This British Standard, having been p
2、repared under the directionof the Health and Environment Sector Board, waspublished under the authorityof the Standards Boardand comes into effect on 15 March 1995 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference EPC/48 Draft for comment 92/59280 DC I
3、SBN 0 580 23842 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee EPC/48, Soil quality, upon which the following bodies were represented: Association of Consulting Scientists Association of County Councils Association of
4、Environmental Consultants Association of Public Analysts British Gas plc British Geological Survey British Society of Soil Science Chemical Industries Association Confederation of British Industry Department of Agriculture Northern Ireland Department of the Environment Department of the Environment
5、(Drinking Water Inspectorate) Department of Trade and Industry 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
6、Land Use Research Institute 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 Cer
7、amic Research Ltd. Institute of Occupational Medicine National Rivers Authority Royal Society of Chemistry Society of Chemical Industry Amendments issued since publication Amd. No. Date Comments 9508 July 1997 Indicated by a sideline in the marginBS7755-3.4:1995 BSI 09-1999 i Contents Page Committee
8、s responsible Inside front cover National foreword ii 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents 1 5 Apparatus and glassware 1 6 Laboratory sample 1 7 Procedure 2 8 Interferences 2 9 Repeatability 2 10 Test report 2 Annex A (informative) Results of an interlaboratory trial for the d
9、etermination of the specific electrical conductivity of soils 3 Table 1 Repeatability 2 Table A.1 Results of an interlaboratory trial for the determination of the specific electrical conductivity 3 List of references Inside back coverBS7755-3.4:1995 ii BSI 09-1999 National foreword This Section of B
10、S7755 has been prepared under the direction of the Health and Environment Sector Board. It is identical with ISO 11265:1994 Soil quality Determination of the specific electrical conductivity, including Technical corrigendum 1:1996, published by the International Organization for Standardization (ISO
11、). ISO11265 was prepared by Subcommittee 3, Chemical methods, of Technical Committee ISO/TC190, Soil quality, with the active participation and approval of the UK. BS7755 is being published in a series of Parts subdivided into Sections and Subsections that will generally correspond to particular Int
12、ernational Standards. Other Parts of BS7755 are, or will be, as follows. Part 1: 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 ISO 7888:1985 to which normative r
13、eference is made in the text, and has decided that they are acceptable for use in conjunction with this 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 in a propos
14、al to amend the text of the International Standard. In Annex A, paragraph 4, line 1, “1 and 4” should be “1 to 4”. 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 Br
15、itish Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding British Standard ISO 3696:1987 BS 3978:1987 Specification for water for laboratory use (Identical) ISO 11464:1994 BS 7755 Soil quality Part 3 Chemical methods Section 3.5:1
16、995 Pretreatment of samples for physico-chemical analyses (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 in
17、corporated. This will be indicated in the amendment table on the inside front cover.BS7755-3.4:1995 BSI 09-1999 1 1 Scope This International Standard specifies an instrumental method for the routine determination of the specific electrical conductivity in an aqueous extract of soil. The determinatio
18、n is carried out to obtain an indication of the content of water-soluble electrolytes in a soil. This International Standard is applicable to all types of air-dried soil samples. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provi
19、sions of this International Standard. 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 standar
20、ds indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 3696:1987, Water for analytical laboratory use Specification and test methods. ISO 7888:1985, Water quality Determination of electrical conductivity. ISO 11464:1994, Soil quality Pretreatmen
21、t of samples for physico-chemical analyses. 3 Principle Air-dried soil is extracted with water at 20 C 1 C at an extraction ratio of 1: 5 (m/V), to dissolve the electrolytes. The specific electrical conductivity of the filtered extract is measured and the result is corrected to a temperature of 25 C
22、. NOTE 1For definitions of the concepts used, see ISO7888. 4 Reagents Use only reagents of recognized analytical grade. 4.1 Water, with a specific electrical conductivity not higher than 0,2 mS/m at 25 C (grade 2 water according to ISO3696). 4.2 Potassium chloride solution, c(KCl) = 0,1mol/l. Dissol
23、ve 7,456g of potassium chloride, previously dried for24h at 220 C 10 C in water (4.1), and dilute to1000ml at 20 C. The specific electrical conductivity of this solution is1290mS/m at 25 C. 4.3 Potassium chloride solution, c(KCl) = 0,020 0 mol/l. Pour 200,0ml of the potassium chloride solution(4.2)
24、into a1000ml volumetric flask and dilute to volume with water at20 C. The specific electrical conductivity of this solution is 277 mS/m at 25 C. 4.4 Potassium chloride solution, c(KCl) = 0,010 0 mol/l. Pour100,0ml of the potassium chloride solution(4.2) into a1000ml volumetric flask and dilute to vo
25、lume with water at 20 C. The specific electrical conductivity of this solution is141mS/m at 25 C. All the potassium chloride solutions (4.2, 4.3 and above) used for calibration shall be stored in tightly sealed bottles which do not release sufficient alkali or alkali-earth cations to affect the elec
26、trical conductivity of the solutions. NOTE 2Plastics bottles may be suitable. NOTE 3For bottles containing potassium chloride solutions, plastics seals are recommended as glass will weld to the bottle. NOTE 4The use of commercially available conductivity standards is permitted. 5 Apparatus and glass
27、ware 5.1 Conductivity meter, fitted with a conductivity cell, equipped with an adjustable measuring range setting and (automatic) temperature correction and having an accuracy of 1mS/m at 20 C. Preferably, the conductivity meter should also be equipped with a cell-constant control. 5.2 Analytical ba
28、lance, with an accuracy of at least0,01g. 5.3 Thermometer, capable of measuring to the nearest0,1 C. 5.4 Shaking machine, with a horizontal movement sufficiently vigorous to produce and maintain a 1 : 5 soil : water suspension, placed in a environment where the temperature adjusted is maintained at2
29、0 C 1 C. NOTE 5Machines with a speed of about 180cycles per minute and a stroke of about5cm have been found suitable. 5.5 Filter paper, with low ash and high retentive properties. 5.6 Shaking bottle, of capacity250ml, made of borosilicate glass or polyethylene. 5.7 Usual laboratory glassware 6 Labor
30、atory sample Use the fraction of particles smaller than2mm of air-dried soil samples pretreated according toISO11464.BS7755-3.4:1995 2 BSI 09-1999 7 Procedure 7.1 Extraction Weigh20,00g of the laboratory sample and transfer to a shaking bottle (5.6). Add 100ml of water (4.1) at a temperature of20 C
31、1 C. Close the bottle and place it in a horizontal position in the shaking machine (5.4). Shake for30min. Filter directly through a filter paper (5.5). Carry out a blank determination in the same way. The value of the blank shall not exceed 1mS/m. If the value of the blank exceeds this, repeat the e
32、xtraction. NOTE 6The volume of filtrate should be just sufficient to perform the measurements. NOTE 7An extraction ratio of 1 : 5 (m/V) is chosen to ensure that an extract is obtainable from all soils including those with high organic matter contents. Using a smaller ratio, it is hardly possible to
33、obtain an extract for some soils. NOTE 8The extraction should be performed at the chosen temperature of 20 C 1 C, because the solubility of the salts present depends on the temperature. After the filtration, the temperature of the extract is allowed to change. The measurement is performed with the t
34、emperature adjusted to25 C. Measurement of the blank is carried out to determine how much the water, glassware and filter paper used contribute to the electrical conductivity of the extracts. NOTE 9The shaking action should be just sufficient to produce and maintain a suspension. More vigorous shaki
35、ng may lead to excessive dispersion of clay, difficulty in filtration and consequent adverse effects on conductivity. 7.2 Checking of the cell constant 7.2.1 Measure the conductance (G) of the potassium chloride solutions (4.2 to 4.4) according to the instruction manual of the instrument. 7.2.2 Calc
36、ulate, for each potassium chloride solution, a cell constant according to where Use the average of the calculated values as the cell constant of the instrument. The calculated cell constant shall not differ by more than5% from the value given by the manufacturer. 7.2.3 Adjust the cell constant on th
37、e conductivity meter. 7.3 Measurement of the electrical conductivity of the filtrates Measure the electrical conductivity of the flitrates ( m ) according to the instructions provided by the manufacturer of the conductivity meter (5.1). Carry out the measurements with the temperature corrected to 25
38、 C. Note the results to one decimal place, expressed in millisiemens per metre. 8 Interferences 8.1 The measured values of the electrical conductivity can be influenced by contamination of the electrodes. This type of interference is very difficult to recognize. Pollution of the electrodes may chang
39、e the cell constant, and this can be perceived by measuring the conductivity of the potassium chloride solutions. 8.2 Air bubbles on the electrodes, for example formed during warming of the extracts, perturb the measurements. 8.3 Measurements of electrical conductivities less than1mS/m are influence
40、d by carbon dioxide and ammonia from the atmosphere. In these cases, measurements shall be carried out in an adapted measuring cell. Such measurements are outside the scope of this International Standard. 9 Repeatability The repeatability of the electrical conductivity measurements in two separately
41、 prepared flitrates shall satisfy the requirements ofTable 1. Table 1 Repeatability 10 Test report The test report shall contain the following information: a) a reference to this International Standard; b) all information necessary for complete identification of the sample; c) the results of the det
42、ermination in whole numbers, expressed in millisiemens per metre; d) details of any operations not specified in this International Standard or regarded as optional, and any other factors which may have affected the results. K is the cell constant, in reciprocal metres; s is the specific electrical c
43、onductivity of one of the potassium chloride solutions, in millisiemens per metre; G is the conductance of the same potassium chloride solution, in millisiemens. K s G - = Electrical conductivity mS/m at 25 C Accepted variation 0 to 50 5 mS/m 50 to 200 20 mS/m 200 10%BS7755-3.4:1995 BSI 09-1999 3 An
44、nex A (informative) Results of an interlaboratory trial for the determination of the specific electrical conductivity of soils In 1991, an interlaboratory trial was organized by the Wageningen Agricultural University to test the procedure specified in this International Standard. For this interlabor
45、atory trial, the determination of the specific electrical conductivity of five soils was carried out by 26 laboratories. The summary of the results of the interlaboratory trials is presented inTable A.1. Samples 1 and 4 mentioned inTable A.1 were collected 1)in salt-affected areas in Hungary. The fi
46、fth sample originates from the Netherlands. The repeatability, r, and the reproducibility, R, given in this table were calculated according to ISO5725:1986, Precision of test methods Determination of repeatability and reproducibility for a standard test method by inter-laboratory tests. Table A.1 Re
47、sults of an interlaboratory trial for the determination of the specific electricalconductivity 1) See national foreword. Sample No. 1 2 3 4 5 Number of laboratories retained after eliminating outliers 26 26 26 25 26 Number of outliers (laboratories) 1 Number of accepted results 52 52 52 50 52 Mean v
48、alue (mS/m) 34,931 117,075 142,673 655,506 31,077 Repeatability standard deviation (s r ) 0,874 3,012 1,717 11,153 1,063 Repeatability relative standard deviation (%) 2,501 2,573 1,203 1,701 3,420 Repeatability limit (r = 2,8 s r ) 2,446 8,434 4,806 31,229 2,976 Reproducibility standard deviation (s
49、 R ) 7,889 9,021 13,340 62,439 4,116 Reproducibility relative standard deviation (%) 22,583 7,705 9,350 9,525 13,244 Reproducibility limit (R = 2,8 s R ) 22,088 25,259 37,352 174,828 11,5244 blankBS7755-3.4:1995 BSI 09-1999 List of references See national foreword.BS 7755-3.4: 1995 ISO 11265: 1994 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standard
