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1、BRITISH STANDARD BS 1747-7: 1983 ISO 4221:1980 Methods for Measurement of air pollution Part 7: Determination of mass concentration of sulphur dioxide in ambient air: Thorin spectrophotometric method ISO title: Air quality Determination of mass concentration of sulphur dioxide in ambient air: Thorin
2、 spectrophotometric method UDC 551.510.42:614.72:551.508.95:546.224-31 Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 03:29:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1747-7:1983 This British Standard, having been prepared under the direction of the Environment and Pollution Standards
3、Committee, was published under the authority of the Board of BSI and comes into effect on 31 January 1983 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference EPC/35 Draft for comment 77/51792 DC ISBN 0 580 13120 3 Cooperating organizations The Environmen
4、t and Pollution Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: Association of County Councils British Gas Corporation* British Industrial Measuring and Control Apparatus Manufacturers Association (BEAMA)* British Paper a
5、nd Board Industry Federation (PIF) British Railways Board British Steel Corporation* Chemical Industries Association Confederation of British Industry Consumer Standards Advisory Committee of BSI Council of Engineering Institutions Council of Environmental Conservation Department of Industry (Labora
6、tory of the Government Chemist)* Department of Industry (Warren Spring Laboratory)* Department of the Environment (Water Directorate) Department of Transport Electricity Supply Industry in England and Wales* Engineering Equipment Users Association Greater London Council Health and Safety Executive*
7、Institute of Petroleum* Medical Research Council Ministry of Agriculture, Fisheries and Food National Coal Board* National Water Council Royal Society of Chemistry Scottish Office Trades Union Congress The organizations marked with an asterisk in the above list, together with the following, were dir
8、ectly represented on the Technical Committee entrusted with the preparation of this British Standard: Cement Makers Federation Department of Health and Social Security Institution of Environmental Health Officers Institution of Gas Engineers Lead Development Association National Industrial Fuel Effi
9、ciency Service National Society for Clean Air Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 03:29:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1747-7:1983 BSI 10-1999i Contents Page Cooperating organizationsInside front c
10、over National forewordii 1Scope1 2Field of application1 3Reference1 4Principle1 5Reagents1 6Apparatus2 7Sampling3 8Procedure3 9Expression of results4 10Test report5 Figure 1 Absorption bottle2 Figure 2 Typical calibration curve obtained using a single-beam spectrophotometer with cells having an opti
11、cal path length of 20 mm5 Figure 3 Typical calibration curve obtained using a single-beam spectrophotometer with cells having an optical path length of 10 mm6 Figure 4 Typical calibration curve obtained using a double-beam spectrophotometer with cells having an optical path length of 20 mm7 Figure 5
12、 Typical calibration curve obtained using a double-beam spectrophotometer with cells having an optical path length of 10 mm8 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 03:29:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1747-7:1983 ii BSI 10-1
13、999 National foreword This Part of this British Standard, which has been prepared under the direction of the Environment and Pollution Standards Committee, is identical with ISO 4221:1980 “Air quality Determination of mass concentration of sulphur dioxide in ambient air Thorin spectrophotometric met
14、hod”. The International Standard was prepared by Technical Committee 146, Air quality, and published by the International Organization for Standardization (ISO) as a result of discussion in which the UK participated. This Part of this British Standard is one of a series relating to air quality arisi
15、ng from the UK participation in the work of ISO/TC 146. Methods for the determination of particular constituents of ambient air will be published as further Parts of this standard. Topics relating to air quality characteristics will be published as Parts of BS 6069 “Methods for characterization of a
16、ir quality”. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to th
17、e following. The comma has been used throughout as a decimal marker. It is current practice in British Standards to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. A Bri
18、tish 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 British Standard does not of itself confer immunity from legal obligations. Cross-reference International StandardCorrespo
19、nding British Standard ISO 4219:1979BS 1747 Methods for measurement of air pollution Part 6:1982 Sampling equipment used for the determination of gaseous sulphur compounds in ambient air (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages
20、1 to 8, 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 inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 03:29:55 GMT+00:00 2006, Uncont
21、rolled Copy, (c) BSI BS 1747-7:1983 BSI 10-19991 1 Scope This International Standard specifies a Thorin1) spectrophotometic method for the determination of the mass concentration of sulphur dioxide in ambient air. 2 Field of application This method is applicable to the determination of the mass conc
22、entration of sulphur dioxide in ambient air within the range of 3,5 to 150 4g/m3, assuming an air sample volume of 2 m3 and a sample solution volume of 50 ml. For higher concentrations, dilution of the sample may be necessary before carrying out the determination.2) Interference from ammonia and hyd
23、rogen sulphide may occur if these are present in very high concentrations. Interferences from particulate matter are avoided at the sampling stage by filtering the air. (See also 8.3.) NOTEDiluting may be sometimes unnecessary if the air sample collected over a specified period is reduced by dividin
24、g the overall sampling period into intervals of the same duration and sampling in such a way that intervals of absorption are followed by intervals where the sampling pump is switched off. 3 Reference ISO 4219, Air quality Determination of gaseous sulphur compounds in ambient air Sampling equipment.
25、 4 Principle Absorption and oxidation of the sulphur dioxide present in the sampled air by drawing the sample for a specified period through an acidified solution of hydrogen peroxide of defined pH, resulting in the formation of sulphuric acid. Precipitation of the sulphate ions formed as barium sul
26、phate by reaction with excess barium perchlorate and determination of residual barium ions by complexing with Thorin and measurement of the coloured complex spectrophotometrically at 520 nm. NOTEThe difference between the initial and final quantity of barium ions corresponds to the concentration of
27、sulphate ions in the absorption solution, and thus to the amount of sulphur dioxide that has been oxidized. The absorbance varies inversely with the concentration of sulphate ions present in the absorption solution. 5 Reagents During the analysis, use only reagents of recognized analytical grade and
28、 only double-distilled or de-ionized and distilled water. WARNING Handle carefully the following hazardous substances: perchloric acid solution, barium perchlorate solution, dioxane and Thorin. 5.1 Hydrogen peroxide, 27 to 30 % (m/m) solution. 5.2 Absorption solution Dilute 10 ml of the hydrogen per
29、oxide solution (5.1) to 1 000 ml with water. Adjust the pH of the solution to between 4,0 and 4,5 with the perchloric acid solution (5.4), preferably using a pH meter. Store this solution in a refrigerator and discard after 1 month. 5.3 Perchloric acid, 0,1 mol/l solution. Add 4,3 ml of a 72 % (m/m)
30、 solution of perchloric acid (HClO4) to water in a 500 ml one-mark volumetric flask. Dilute to the mark and mix. 5.4 Perchloric acid, approximately 0,01 mol/l solution. Prepare from the 0,1 mol/l solution (5.3). 5.5 Barium perchlorate solution. Dissolve 0,525 g of anhydrous barium perchlorate Ba (Cl
31、O4)2 in a small quantity of the perchloric acid solution (5.3) in a 250 ml one-mark volumetric flask. Dilute to the mark with the same perchloric acid solution and mix. 5.6 Barium perchlorate/dioxane solution Add 10 ml of the barium perchlorate solution (5.5) to 40 ml of water in a 1 000 ml one-mark
32、 volumetric flask. Dilute to the mark with dioxane and mix. NOTE 1Several organic solvents may be used, for example dioxane, isopropanol, acetone. The most favourable calibration curve, however, is obtained with dioxane. NOTE 2The organic solvent is chosen to minimize the solubility product of the b
33、arium sulphate, but because this is still significant in the lower region of the concentration range, a small constant amount of sulphate ion is added to the blank solution, the standard matching solutions and the aliquot portion of the exposed sample. 5.7 Thorin, 2,5 g/l solution. Dissolve 0,125 g
34、of Thorin in 20 ml of the standard sulphate solution (5.8.2) and a small quantity of water in a 50 ml one-mark volumetric flask. Dilute to the mark with water and mix. Prepare this solution daily. 1) Thorin is also known as Thoron or Thoronol, the sodium salt of 4-(2-arsonophenyl) azo3-hydroxy 2,7-n
35、aphthalene-disulphonic acid. 2) An International Standard specifying a tetrachloromercurate (TCM)/pararosaniline spectrophotometric method for the determination of the mass concentration of sulphur dioxide in ambient air is in preparation, and should be used when greater sensitivity is required. Lic
36、ensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 03:29:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1747-7:1983 2 BSI 10-1999 5.8 Standard sulphate solutions 5.8.1 Sulphate, standard solution containing 0,5 mol of sulphuric acid (H2SO4) per litre. Standardize this solution accurately by titra
37、tion against a standard volumetric sodium hydroxide solution, which has been standardized itself against potassium hydrogen phthalate (KHC8H4O4). 1 ml of this standard solution corresponds to 32 mg of SO2. 5.8.2 Sulphate, standard solution containing 0,001 25 mol of sulphuric acid (H2SO4) per litre.
38、 Prepare from the standard sulphate solution (5.8.1) by diluting as follows: a) Measure by pipette 25 ml of the standard sulphate solution into a 1 000 ml one-mark volumetric flask. Dilute to the mark with water and mix. 1 ml of this standard solution corresponds to about 800 4g of SO2. b) Measure b
39、y pipette 10 ml of the standard sulphate solution obtained in a) into a 100 ml one-mark volumetric flask. Dilute to the mark with water and mix. 1 ml of this standard solution corresponds to about 80 4g of SO2. 6 Apparatus Ordinary laboratory apparatus and 6.1 Sampling equipment as specified in ISO
40、4219, subclauses 5.1 to 5.7 and, in addition, as specified in 6.1.1. 6.1.1 Absorption bottles Borosilicate glass bottles of the Drechsel type equipped with interchangeable ground glass joints (see Figure 1) shall be used. A bottle having the cone of the ground glass joint on the bottle is preferable
41、, because of the smaller risk of deposited matter dropping into the absorption solution when the sampling head is removed. The capacity of the bottle shall be 125 ml for 24 h sampling and 250 ml for 48 h sampling. The external diameter of the entry and exit tubes of the absorption bottle shall be 10
42、 mm to 12 mm. The tube leading the air into the solution shall have an internal diameter of 6 to 8 mm and shall end 5 to 10 mm from the bottom of the bottle. Figure 1 Absorption bottle (The dimensional proportions are approximate.) Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 03:29:55 GMT+
43、00:00 2006, Uncontrolled Copy, (c) BSI BS 1747-7:1983 BSI 10-19993 6.2 Spectrophotometer, single-or double-beam type If a single-beam spectrophotometer is to be used, it shall be possible to adjust the incident light intensity, for example, by adjusting a diaphragm or by slit-width control. For a si
44、ngle-beam spectrophotometer, the greatest accuracy is achieved if the incident light beam intensity can be adjusted to give a “read absorbance” value as close to 0 as possible for the highest measurable concentration. However, with the instruments currently available, the best possible result is obt
45、ained if the adjusted light intensity results in a “read absorbance” value of 0,800 for the blank solution in a 10 mm or 20 mm cell. Using a double-beam instrument, the difference in the absorbance between the sample (or the standard solutions) and the blank can be read directly. NOTEread absorbance
46、 value: The reading value on the face of a single-beam spectrophotometer; the measured signal is proportional to the logarithm of the intensity. 6.3 Glass cells, having an optical path length of 10 or 20 mm. If more than one cell is used, the cells shall be matched photometrically. 6.4 Pipettes, of
47、capacity 0,25 ml, or dispensing and diluting apparatus. 7 Sampling Set up the equipment specified in ISO 4219 in accordance with the requirements of ISO 4219 and any special requirements for the atmosphere to be sampled (see 8.3). Insert a particulate filter (5.3 of ISO 4219) into the filter holder
48、(5.3.2 of ISO 4219). In one of the absorption bottles (6.1.1) place a suitable quantity of the absorption solution (5.2), mark the level of the solution and connect the bottle to the sample train. For a sampling period of 24 h, the volume used shall be 50 ml and for a sampling period of 48 h 150 ml.
49、 NOTE 1 If the temperature of the air sampled exceeds 25 C or if the air is very dry, larger volumes of absorption solution may have to be used. The correct amount needed to absorb all the sulphur dioxides in the test sample collected during the selected test duration should be ascertained by preliminary tests. NOTE 1Automatic equipment for changing the absorption bottles may be used. Adjust the flow regulator (5.6 of ISO 4219) to give a flow rate of 90 l/h. Record the reading on the gas meter (5.6 of ISO 4219) and the time and start the sampling