1、BRITISH STANDARD BS 7755-3.8: 1995 ISO10694: 1995 Soil quality Part 3: Chemical methods Section 3.8 Determination of organic and total carbon after dry combustion (elementary analysis)BS7755-3.8:1995 This British Standard, having been prepared under the directionof the Health and Environment Sector
2、Board, waspublished under the authorityof the Standards Board and comes into effect on 15 October 1995 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference EH/4/3 Draft for comment 94/501661 DC ISBN 0 580 24693 0 Committees responsible for this British St
3、andard The preparation of this British Standard was entrusted by Technical Committee EH/4, Soil quality, to Subcommittee EH/4/3, Chemical methods, upon which the following bodies were represented: Association of Consulting Scientists Association of Public Analysts British Ceramic Research Ltd. Briti
4、sh Gas plc British Society of Soil Science Department of the Environment (Drinking Water Inspectorate) Department of Trade and Industry (Laboratory of the Government Chemist) National Rivers Authority Royal Society of Chemistry Society of Chemical Industry Soil Survey and Land Research Centre Water
5、Research Centre Water Services Association of England and Wales Amendments issued since publication Amd. No. Date CommentsBS7755-3.8:1995 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents 1 5 Apparat
6、us and glassware 1 6 Laboratory sample 1 7 Procedure 2 8 Calculations 2 9 Repeatability 3 10 Test report 3 Annex A (informative) Results of interlaboratory trials 4 Annex B (informative) Bibliography 5 Table 1Repeatability 3 Table A.1 Types of soils used for the interlaboratory trial and their origi
7、n 4 Table A.2 Results of the interlaboratory trial for the determination oforganiccarbon in soil 4 Table A.3 Results of the interlaboratory trial for the determination oftotalcarbon in soil 5 List of references Inside back coverBS7755-3.8:1995 ii BSI 07-1999 National foreword This British Standard h
8、as been prepared by Subcommittee EH/4/3 and is identical with ISO 10694:1995 Soil quality Determination of organic and total carbon after dry combustion (elementary analysis), published by the International Organization for Standardization (ISO). ISO 11263 was prepared by Subcommittee 3, Chemical me
9、thods, of Technical Committee ISO/TC 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
10、will be, as follows. Part 1: Terminology and classification; Part 2: Sampling; Part 3: Chemical methods; Part 4: Biological methods; Part 5: Physical methods. ISO 10693 is not yet published; on publication it is intended for it to be implemented as a Section of BS 7755. In the meantime, the Technica
11、l Committee has reviewed the provisions of this standard, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards
12、are responsible for their correct application. Compliance with a British 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 10
13、390 BS 7755 Soil quality Section 3.2:1995 Determination of pH (Identical) ISO 11464:1994 Section 3.5:1995 Pretreatment of samples for physico-chemical analyses (Identical) ISO 11465:1993 Section 3.1:1994 Determination of dry matter and water content on a mass basis by a gravimetric method (Identical
14、) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the insi
15、de front cover.BS7755-3.8:1995 BSI 07-1999 1 1 Scope This International Standard specifies a method for the determination of the total carbon content in soil after dry combustion. The organic carbon content is calculated from this content after correcting for carbonates present in the sample. If car
16、bonates are removed beforehand, the organic carbon content is measured directly. 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 provisions of this In
17、ternational 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 standards indicated bel
18、ow. 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 10390:1994, Soil quality Determination of pH. ISO 10693:1995, Soil quality Determination of carbonate content Volumetric me
19、thod 1) . ISO 11464:1994, Soil quality Pretreatment of samples for physico-chemical analyses. ISO 11465:1993, Soil quality Determination of dry matter and water content on a mass basis Gravimetric method. 3 Principle The carbon present in the soil is oxidized to carbon dioxide (CO 2 ) by heating the
20、 soil to at least900 C in a flow of oxygen-containing gas that is free from carbon dioxide. The amount of carbon dioxide released is then measured by titrimetry, gravimetry, conductometry, gas chromatography or using an infrared detection method, depending on the apparatus used. When the soil is hea
21、ted to a temperature of at least900 C, any carbonates present are completely decomposed. For the determination of the organic carbon content, any carbonates present are previously removed by treating the soil with hydrochloric acid. Alternatively, if the carbonate content of the examined samples is
22、known and corrections are made for the carbonates present when the organic carbon content is calculated. NOTE 1When the pH-CaCl 2is less than6,5, the presence of carbonates is unlikely. For example, this combination of low pH and presence of carbonates is only possible in recently limed soils. 4 Rea
23、gents Use only reagents of recognized analytical grade and distilled or deionized water for all solutions. 4.1 Water, with an electrical conductivity not higher than0,2mS/m at25 C (grade2water according to ISO3696). 4.2 Calibration substances, e.g. acetanilide (C 8 H 9 NO), atropine (C 17 H 23 NO 3
24、), calcium carbonate (CaCO 3 ), spectrographic graphite powder (C) and potassium hydrogen phthalate (C 8 H 5 KO 4 ). 4.3 Hydrochloric acid, c(HCl) =4mol/l. Dilute340ml of concentrated hydrochloric acid ( =1,19g/ml) to1000ml with water(4.1). NOTE 2Depending on the method of detection used, reagents a
25、nd/or catalysts may be required for reduction, oxidation, removal and/or fixing of combustion gases which interfere with the analysis. The manufacturers manual should be consulted for the apparatus to be used. 5 Apparatus and glassware 5.1 Standard laboratory glassware 5.2 Analytical balance (capabl
26、e of weighing accurately to0,1mg) or microbalance (capableofweighing accurately to0,01mg). 5.3 Apparatus for determination of the total carbon content, by combustion of the sample at a temperature of at least900 C, including a detector for measuring the carbon dioxide formed. NOTE 3The following det
27、ection methods are currently available: titrimetry, gravimetry, conductometry, gas chromatography and infrared measurement. NOTE 4Some modern instruments are capable of determining organic and inorganic carbon separately in one run, by increasing the temperature gradually and continuously measuring
28、the carbon dioxide. NOTE 5Some instruments are capable of simultanuously determining total nitrogen and total carbon in soils. 5.4 Crucibles, made of porcelain, quartz, silver, tin or nickel, of various sizes. NOTE 6Tin or nickel crucibles are not acid-resistant. 6 Laboratory sample Use the fraction
29、 of particles less than2mm of air-dried soil samples pretreated according to ISO11464. Use part of the laboratory sample to determine the water content according to ISO11465 and, if necessary, the carbonate content according to ISO10693. 1) To be published.BS7755-3.8:1995 2 BSI 07-1999 7 Procedure T
30、he procedure consists of the determination of either a) the total carbon content including that carbon present as carbonate; or b) the organic carbon content after removal of carbonate. NOTE 7The total organic carbon content may be calculated by determining the total carbon content and subtracting t
31、he carbon present as carbonate which can be determined according to ISO10693. 7.1 Calibration of the apparatus Calibrate the apparatus as described in the relevant manual. For calibration or establishing a calibration graph, use one of the substances listed in4.2. 7.2 Determination of the total carb
32、on content The amount of test portion taken for analysis depends on the expected total carbon content and on the apparatus used. Weigh out m 1g of the air-dried sample in a crucible (5.4). Carry out the analyses in accordance with the manufacturers manual for the apparatus. When the organic carbon c
33、ontent is to be determined, the carbonates present shall be removed first. In this case, follow the procedure described in7.3. 7.3 Determination of the organic carbon content Add an excess of hydrochloric acid (4.3) to the crucible containing a weighed quantity of air-dried soil (see7.2) and mix. Wa
34、it4h and dry the crucible for16h at a temperature of60 C to70 C. Then carry out the analysis in accordance with the manufacturers manual for the apparatus. NOTE 8The quantity of hydrochloric acid to be added depends on the weighed amount of test portion and on the carbonate content. In all cases, an
35、 excess of hydrochloric acid should be added, which can be estimated by assuming that the quantity of the sample to be analysed consists of100% carbonates. SAFETY PRECAUTIONS The crucibles used should be large enough to avoid problems when transporting crucibles containing samples to which hydrochlo
36、ric acid has been added. 8 Calculations 8.1 Total carbon content Calculate the total carbon content of the sample, on the basis of oven-dried soil, using the following equation: where 8.2 Organic carbon content 8.2.1 Organic carbon content (indirectdetermination) Calculate the organic carbon content
37、 of the sample, on the basis of oven-dried soil, using the following equation: where w C,t is the total carbon content, ingramsperkilogram, on the basis of oven-dried soil; m 1 is the mass, in grams, of the test portion; m 2 is the mass, in grams, of carbon dioxide released by the soil sample; 0,272
38、 7 is the conversion factor for CO 2to C; is the water content, expressed as a percentage by mass, on a dry mass basis, determined according to ISO 11465. w C,o is the organic carbon content, ingramsper kilogram, on the basis of oven-dried soil; w C,t is the total carbon content, ingramsper kilogram
39、, on the basis of oven-dried soil, calculated according to 8.1; 0,12 is the conversion factor; is the carbonate content of the soil, in grams per kilogram, expressed as calcium carbonate equivalent on the basis of oven-dried soil, determined according to ISO 10693. w H 2 O w CaCO 3BS7755-3.8:1995 BS
40、I 07-1999 3 8.2.2 Organic carbon content (directdetermination) If the carbonates are removed beforehand (followingthe procedure described in7.3), the organic carbon content is determined according to8.1. 8.3 Organic matter content The organic matter content of the soil sample can be calculated from
41、the organic carbon content using the following equation: w om= f w C,o where NOTE 9The conversion factor depends on the type of organic matter and, for agricultural soils, may vary between1,7and2,0. 9 Repeatability The repeatability of the determination of the carbon content carried out in two separ
42、ate consecutive executed measurements shall satisfy the conditions given inTable 1. Table 1 Repeatability The results of an interlaboratory trial for the determination of total carbon and organic carbon in five soils are given inAnnex A. 10 Test report The test report shall contain the following inf
43、ormation: a) a reference to this International Standard; b) a reference to the method used; c) all information necessary for complete identification of the sample; d) the result of the determination for total carbon and/or organic carbon, in grams per kilogram, calculated on the basis of oven-dried
44、soil; when the organic carbon content is determined, it shall be stated whether the carbonate content was determined, or whether carbonates were removed prior to the determination; e) details of any operation not specified in this International Standard or regarded as optional, as well as any factor
45、 which may have affected the results. w om is the organic matter content of the soil, ingrams per kilogram, on the basis of oven-dried soil; w C,o is the organic carbon content of the soil, ingrams per kilogram, on the basis of oven-dried soil; f is a conversion factor. Carbon content Acceptable var
46、iation g/kg greater than up to and including 0,0 2,5 0,25 g/kg absolute 2,5 75 10 % relative 75 7,5 g/kg absoluteBS7755-3.8:1995 4 BSI 07-1999 Annex A (informative) Results of interlaboratory trials An interlaboratory trial was organized in1993by the Wageningen Agricultural University, in the Nether
47、lands, to verify the procedures specified in this International Standard. For this interlaboratory trial, the determination of the organic and total carbon content in five soil samples was carried out by nine laboratories. Results were received from eight laboratories for organic carbon and also for
48、 total carbon. The types of soils used and their origin are listed inTable A.1. The repeatability (r) and the reproducibility (R) of the results of the analyses obtained by the laboratories are presented inTable A.2 and Table A.3. The values were calculated according to ISO 5725-2:1994, Accuracy (tr
49、ueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method. Table A.1 Types of soils used for the interlaboratory trial and their origin Table A.2 Results of the interlaboratory trial for the determination of organic carbon in soil Soil No. Soil type Origin 1 Muck soil Poland 2 Andosol Indonesia 3 Garden soil Netherlands 4 Loess under forest Switzerland 5 Sandy soil Mali Parameter Results Soil No. 1 2 3 4 5 Number
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