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1、BRITISH STANDARD BS 6068-2.18: 1986 Water quality Part 2: Physical, chemical and biochemical methods Section 2.18 Methods for determination of easily liberatable cyanide UDC 556.11 + 614.777 + 628.1/.3 + 663.63:53/54 Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:11 GMT+00:00 2006, Unc
2、ontrolled Copy, (c) BSI BS 6068-2.18:1986 This British Standard, having been prepared under the direction of the Environment and Pollution Standards Committee, was published under the authority of the Board of BSI and comes into effect on 28 February 1986 BSI 10-1999 The following BSI references rel
3、ate to the work on this standard: Committee reference EPC/44 Draft for comment 82/56062 DC ISBN 0 580 14988 9 Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.18:1986
4、 BSI 10-1999i Contents Page Forewordii 0Introduction1 1Scope and field of application1 2Definition2 Subsection 1. Liberation and absorption of hydrogen cyanide 3Principle3 4Reagents3 5Apparatus3 6Sampling and samples3 7Procedure5 Subsection 2. Determination of cyanide ions Photometric method with py
5、ridine/barbituric acid 8Applicability6 9Principle6 10Reagents6 11Apparatus6 12Procedure6 13Expression of results7 14Precision7 15Test report7 Subsection 3. Determination of cyanide ions Titrimetric method using the Tyndall effect 16Applicability8 17Principle and reactions8 18Reagents8 19Apparatus8 2
6、0Procedure9 21Expression of results9 22Precision9 23Test report9 Subsection 4. Determination of cyanide ions Titrimetric method using an indicator 24Applicability11 25Principle11 26Reagents11 27Apparatus11 28Procedure11 29Expression of results11 30Test report11 Figure 1 Apparatus for separation of h
7、ydrogen cyanide by stripping4 Figure 2 Apparatus for determination of cyanide ions using Tyndall effect8 Table 1 Interference2 Table 2 Precision data (photometric method)7 Table 3 Precision data (titrimetric method)10 Bibliography12 Publications referred toInside back cover Licensed Copy: sheffieldu
8、n sheffieldun, na, Tue Dec 05 01:28:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.18:1986 ii BSI 10-1999 Foreword This Section of this British Standard, which has been prepared under the direction of the Environment and Pollution Standards Committee, is based on ISO 6703-2:1984 “Water qual
9、ity Determination of cyanide Part 2: Determination of easily liberatable cyanide” but is not equivalent in technical content. ISO 6703-2 was prepared by subcommittee 2, Physical, chemical and biochemical methods, of Technical Committee 147, Water quality, of the International Organization for Standa
10、rdization (ISO) as a result of discussion in which the UK participated. For ease of publication, the text of ISO 6703-2 has been used as a basis for this Section of this British Standard and a number of amendments have been incorporated. The principal changes now incorporated are that the text has b
11、een amplified, to improve clarity and avoid misunderstandings in the following clauses: 1, 8, 12.2, 13, 16, 20, 21, 24, and 29. In addition clause 8 now allows the use of smaller test portions in addition to dilution of absorption solutions with the sodium hydroxide solution. This British Standard i
12、s being published in a series of Parts subdivided into Sections that will generally correspond to particular International Standards. Sections are being, or will be, published in Parts 1 to 6, which, together with Part 0, are listed below. Part 0: Introduction; Part 1: Glossary; Part 2: Physical, ch
13、emical and biochemical methods; Part 3: Radiological methods; Part 4: Microbiological methods; Part 5: Biological methods; Part 6: Sampling. Terminology and conventions. As a result of using the ISO text some terminology and certain conventions are not identical with those used in British Standards;
14、 attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. In British Standards it is current practice to use the symbol “L” for litre (and its submultiples) rath
15、er than “l” and to use the spelling “sulphur” etc., instead of “sulfur”, etc. Additional information. If a high intensity beam of light is passed through a colloidal solution and the solution viewed at a right angle to the incident light, a scattering of light is observed. This is known as the Tynda
16、ll effect. 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 British Standard does not of itself confer immunity from legal obligations. Summary of pages This document
17、 comprises a front cover, an inside front cover, pages i and ii, pages 1 to 12, 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:
18、 sheffieldun sheffieldun, na, Tue Dec 05 01:28:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.18:1986 BSI 10-19991 Attention is drawn to the toxicity of cyanide and to the need to take extreme care when handling cyanides and their solutions. Carry out all operations in a fume cupboard. Avoi
19、d contact with the skin and eyes. When pipetting, always use a safety pipette (pipette by bulb). Detoxify samples and solutions containing cyanides or heavy metals in accordance with local official regulations. Other chemical specified in this Section of this British Standard are also hazardous, for
20、 example pyridine. 0 Introduction Cyanides may be present in water as hydrocyanic acid (prussic acid), as cyanide ions and as complex cyanides. They may be determined as total cyanide or as easily liberatable cyanide. If cyanide compounds are chlorinated, cyanogen chloride (CICN) is produced, and th
21、is compound has to be determined separately. There are 4 Sections in BS 6068 for the determination of cyanides in water as follows: BS 6068-2.17:1986, Methods for determination of total cyanide. BS 6068-2.18:1986, Methods for determination of easily liberatable cyanide. BS 6068-2.19:1986, Method for
22、 determination of cyanogen chloride. BS 6068-2.20:1986, Method for determination of cyanide by diffusion at pH 6. The methods described in Sections 2.17, 2.18 and 2.19 are suitable for controlling the quality of water and for the examination of municipal sewage and industrial effluents. They are app
23、ropriate to the technology available for the destruction of cyanides in treatment plants, and are based on the separation of liberated hydrogen cyanide (or in the case of BS 6068-2.19, of cyanogen chloride) by stripping with a carrier gas. The method specified in BS 6068-2.20, using diffusion separa
24、tion, is suitable for the determination of smaller amounts of cyanide, depending on the concentrations of copper and nickel. This Section of this British Standard comprises 4 subsections. Subsection 1 deals with the liberation and absorption of hydrogen cyanide. The other 3 subsections deal with alt
25、ernative methods for the quantitative determination of cyanide ions, as follows: photometric method with pyridine/barbituric acid (subsection 2); titrimetric method using the Tyndall effect (subsection 3); titrimetric method using an indicator (subsection 4). The specification of three alternative m
26、ethods is necessary because each of the methods has its advantages and disadvantages. None can be quoted as applicable in all cases. The applicability of each method is described in clauses 8, 16 and 24. NOTEDue to the different chemical behaviour of cyanide-containing or cyanide-producing substance
27、s, it is not possible to specify only one method for the quantitative determination of cyanide ions. 1 Scope and field of application This Section of this British Standard specifies three methods for the determination of easily liberatable cyanide (see clause 2) in water. The methods are applicable
28、to water containing less than 50 mg of easily liberatable cyanide (as cyanide ions) per litre, and less than 100 mg of total cyanide (as cyanide ions) per litre, but higher concentrations may be determined by suitable dilution of the sample. The methods and corresponding ranges of easily liberatable
29、 cyanide contents for which they are suitable are as follows: Photometric method with pyridine/barbituric acid: applicable when the absorption solution contains 0,002 to 0,025 mg of cyanide, corresponding to 0,02 to 0,25 mg/l in a 100 ml aliquot portion of the undiluted sample; Titrimetric method us
30、ing the Tyndall effect: applicable when the absorption solution contains 0,005 mg of cyanide, corresponding to 0,05 mg/l in a 100 ml aliquot portion of the undiluted sample; Titrimetric method using an indicator: applicable when the absorption solution contains 0,05 mg of cyanide, corresponding to 0
31、,5 mg/l in a 100 ml aliquote portion of the undiluted sample. A large number of ions and compounds interfere with the determination. These are listed in Table 1, together with the concentrations below which they do not interfere. If present singly or in combination, up to limiting concentrations, th
32、ey do not interfere with the separation of hydrogen cyanide. The list is not exhaustive. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.18:1986 2 BSI 10-1999 Table 1 InterferencesIf any of the limiting concentrations of the influe
33、nces are likely to be exceeded, dilute the sample with distilled water before stabilization (see clause 6). Prussiates (pentacyano complexes with iron), which cannot be destroyed by chlorination under normal conditions of waste water treatment, partly decompose (up to 50 %), releasing hydrocyanic ac
34、id under the conditions specified. If it is desired to exclude prussiates, the procedure specified in clause 6 and 7.1 has to be used. This procedure is only applicable, however, if the concentration of copper ions in the sample is less than 1 mg/l. The presence of aldehydes, e.g. formaldehyde, may
35、give lower cyanide values because of the formation of cyanohydrin. 2 Definition For the purpose of this Section of this British Standard the following definition applies. easily liberatable cyanide cyanide from substances with cyanide groups and a measurable hydrocyanic acid vapour pressure at pH 4
36、and room temperature such substances include all cyanides which will undergo chlorination, especially hydrocyanic acid, alkali- and alkali earth metal cyanides, and complex cyanides of zinc, cadmium, silver, copper and nickel. Complex cyanides of iron and cobalt, nitriles, cyanates, thiocyanates and
37、 cyanogen chloride are not included InterferenceLimiting concentration, mg/l Sulfide ions Polysulfide ions Sulfide and polysulfide ions Sulfide ions Thiosulfate ions Thiocyanate ions Carbonate ions Cyanate ions Nitrate ions Nitrite ions Ammonium ions Iron(II) and iron(III) ions Copper(II) ions Nicke
38、l(II) ions Silver ions Mercury ions Chromate ions Propionic acid Phenol Anthracene Naphthalene Anisaldehyde Piperonal Pyrrole Pyridine Chlorine (elemental) Hydrogen peroxide Perborate ions 1 000 500 1 000 500 1 000 1 000 1 000 1 000 500 500 2 000 5 000 100 50 50 50 300 1 000 1 000 100 100 10 10 100
39、10 250 10 10 Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.18:1986 BSI 10-19993 Subsection 1. Liberation and absorption of hydrogen cyanide 3 Principle Liberation of hydrogen cyanide from the sample by treatment at pH 4 with meta
40、llic zinc and EDTA. Entrainment of the hydrogen cyanide in a current of air into an absorption vessel containing sodium hydroxide solution. 4 Reagents All reagents shall be of recognized analytical grade and the water used shall be distilled or deionized water. 4.1 Hydrochloric acid, solution, 1,12
41、g/ml. 4.2 Hydrochloric acid, solution, c(HCl) = 1 mol/l. 4.3 Sodium hydroxide, solution, c(NaOH) = 1 mol/l. 4.4 Sodium hydroxide, solution, c(NaOH) = 5 mol/l. 4.5 Tin(II) chloride, solution. Dissolve 50 g of tin(II) chloride dihydrate (SnCl2.2H2O) in 40 ml of the hydrochloric acid solution (4.2) and
42、 dilute with water to 100 ml. Prepare a fresh solution each week. 4.6 Phenolphthalein, solution, containing chloroform. Dissolve 0,03 g of phenolphthalein in 90 ml of ethanol and add 10 ml of chloroform. 4.7 Zinc- and cadmium sulfate, solution.1) Dissolve 100 g of zinc sulfate heptahydrate (ZnSO4.7H
43、2O) and 100 g of cadmium sulfate octahydrate (3CdSO4.8H2O) in water and dilute with water to 1 000 ml. 4.8 Buffer solution, of pH 4,0. Dissolve 80 g of potassium hydrogen phthalate (C8H5KO4) in 920 ml of warm water. 4.9 EDTA, solution. Dissolve 100 g of ethylenedinitrilotetraacetic acid, disodium sa
44、lt dihydrate (C10H14N2Na2O8.2H2O) in 940 ml of warm water. 4.10 Zinc dust 5 Apparatus Usual laboratory equipment, and 5.1 Apparatus for the separation of hydrogen cyanide by stripping The apparatus shown in Figure 1, or its equivalent, is recommended and comprises the following components. 5.1.1 Thr
45、ee-necked distillation flask, of capacity 500 ml, with standard conical joints (centre neck 29/32, side necks 14,5/23). 5.1.2 Reflux condenser (Liebig condenser) 5.1.3 Absorption vessels, protected against return of liquid. 5.1.4 Funnel 5.1.5 Flowmeter 5.1.6 Wash bottle, of capacity 250 ml, for puri
46、fication of the air. 5.2 pH meter, with a glass electrode which will fit into the side necks of the distillation flask. 5.3 One-mark volumetric flasks, of capacities 25, 50, 250 and 1 000 ml. 6 Sampling and samples 6.1 If the sample contains undissolved cyanides, it is necessary to ensure homogeneou
47、s distribution of the undissolved substances in the sample and its dilutions. Immediately after sampling, add 5 ml of the sodium hydroxide solution (4.4), 10 ml of the phenolphthalein solution (4.6) and 5 ml of the tin(II) chloride solution (4.5) to each litre of sample or diluted sample. Adjust the
48、 pH to about 8 by adding the hydrochloric acid solution (4.2), or the sodium hydroxide solution (4.3), drop by drop, until the water turns slightly red. Adjust the pH value of highly coloured samples in the same way after checking with the pH-meter (5.2) or with an indicator paper. Finally, add 10 m
49、l of the zinc- and cadmium sulfate solution (4.8) to each litre of sample. Analyse the sample as soon as possible. If it is necessary to store it, keep it cool and in the dark. After addition of the zinc- and cadmium sulfate solution, a precipitate which may contain hexacyanoferrate, is formed. Accordingly, the sample should be rendered homogeneous immediately prior to taking aliquot portions. If replicate determinations are to be carried out, the aliquot portions shall be taken as quickly as possible in order to minimize any
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