1、BRITISH STANDARD CONFIRMED FEBRUARY1990 BS6068-2.17: 1986 Water quality Part2: Physical, chemical and biochemical methods Section2.17 Methods for determination of total cyanide UDC 556.11+614.777+628.1/.3+663.63:53/54BS6068-2.17:1986 This British Standard, having been prepared under the directionof
2、the Environment andPollution Standards Committee, was published underthe authorityofthe Boardof BSIandcomes into effect on 28 February1986 BSI 06-1999 The following BSI references relate to the work on this standard: Committee reference EPC/44 Draft for comment82/56061 DC ISBN 0580 14987 0 Amendment
3、s issued since publication Amd. No. Date of issue CommentsBS6068-2.17:1986 BSI 06-1999 i Contents Page Foreword ii 0 Introduction 1 1 Scope and field of application 1 2 Definition 2 Subsection 1. Liberation and absorption of hydrogen cyanide 3 Principle 3 4 Reagents 3 5 Apparatus 3 6 Sampling and sa
4、mples 3 7 Procedure 5 Subsection 2. Determination of cyanide ions Photometric method with pyridine/barbituric acid 8 Applicability 6 9 Principle 6 10 Reagents 6 11 Apparatus 6 12 Procedure 6 13 Expression of results 7 14 Precision 7 15 Test report 7 Subsection 3. Determination of cyanide ions Titrim
5、etric method using the Tyndall effect 16 Applicability 8 17 Principle and reactions 8 18 Reagents 8 19 Apparatus 8 20 Procedure 8 21 Expression of results 9 22 Precision 9 23 Test report 9 Subsection 4. Determination of cyanide ions Titrimetric method using an indicator 24 Applicability 11 25 Princi
6、ple 11 26 Reagents 11 27 Apparatus 11 28 Procedure 11 29 Expression of results 11 30 Test report 11 Bibliography 13 Figure 1 Apparatus for separation of hydrogen cyanide by stripping 4 Figure 2 Apparatus for determination of cyanide ions using Tyndall effect 9 Table 1 Interferences 2 Table 2 Precisi
7、on data (photometric method) 7 Table 3 Precision data (titrimetric method) 10 Publications referred to Inside back coverBS 6068-2.17:1986 ii BSI 06-1999 Foreword This Section of this British Standard, which has been prepared under the direction of the Environment and Pollution Standards Committee, i
8、s based on ISO6703/1-1984 “Water quality Determination of cyanide Part1:Determination of total cyanide” but is not equivalent in technical content. ISO6703/1 was prepared by subcommittee2, Physical, chemical and biochemical methods, of Technical Committee147, Water quality, of the International Orga
9、nization for Standardization (ISO) as a result of discussion in which the UK participated. For ease of publication, the text of ISO6703/1 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 t
10、hat the text has been amplified, to improve clarity and avoid misunderstandings in the following clauses:1, 8, 12.2, 13, 16, 20, 21, 24, and29. Clause8 now allows the use of smaller test portions in addition to dilution of absorption solutions with the sodium hydroxide solution. This British Standar
11、d is 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 Parts1 to6, which, together with Part0, are listed below. Part 0: Introduction; Part 1: Glossary; Part 2: Physical, ch
12、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;
13、 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
14、er than “I” 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
15、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
16、 comprises a front cover, an inside front cover, pagesi andii, pages1to12, 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.BS 6068-2.17:1986 BS
17、I 06-1999 1 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. Avoid contact with the skin and eyes. When pipetting, always use a safety pipette (pipette by bulb). Detoxify sample
18、s and solutions containing cyanides or heavy metals in accordance with local official regulations. Other chemicals specified in this Section of this British Standard are also hazardous, for example pyridine. 0 Introduction Cyanides may be present in water as hydrocyanic acid (prussic acid), as cyani
19、de ions and as complex cyanides. They may be determined as total cyanide or as easily liberatable cyanide, if cyanide compounds are chlorinated, cyanogen chloride (ClCN) is produced, and this compound has to be determined separately. There are four Sections in BS6068 for the determination of cyanide
20、s in water as follows: BS6068:2.17:1986, Methods for determination of total cyanide. BS6068:2.18:1986, Methods for determination of easily liberatable cyanide. BS6068:2.19:1986, Method for determination of cyanogen chloride. BS6068:2.20:1986, Method for determination of cyanide by diffusion at pH6.
21、The methods described in Sections2.17,2.18 and2.19 are suitable for controlling the quality of water and for the examination of municipal sewage and industrial effluents. They are appropriate to the technology available for the destruction of cyanides in treatment plants, and are based on the separa
22、tion of liberated hydrogen cyanide (or in the case of BS6068-2.19, of cyanogen chloride) by stripping with a carrier gas. The method specified in BS6068-2.20, using diffusion separation, is suitable for the determination of smaller amounts of cyanide, depending on the concentrations of copper and ni
23、ckel. This Section of this British Standard comprises four subsections. Subsection1 deals with the liberation and absorption of hydrogen cyanide. The other three subsections deal with alternative methods for the quantitative determination of cyanide ions, as follows: photometric method with pyridine
24、/barbituric acid (subsection2); titrimetric method using the Tyndall effect (subsection3); titrimetric method using an indicator (subsection4). The specification of three alternative methods is necessary because each of the methods has its advantages and disadvantages. None can be quoted as applicab
25、le in all cases. The applicability of each method is described in clauses8, 16 and24. NOTEDue to the different chemical behaviour of cyanide-containing or cyanide-producing substances, it is not possible to specify only one method for the quantitative determination of cyanide ions. 1 Scope and field
26、 of application This Section of this British Standard specifies three methods for the determination of total cyanide (seeclause2) in water. The methods are applicable to water containing less than100mg of cyanide per litre, but higher concentrations may be determined by suitable dilution of the samp
27、le. The methods and corresponding ranges of cyanide contents for which they are suitable are as follows: Photometric method with pyridine/barbituric acid: applicable when the absorption solution contains0,002 to0,025mg of cyanide, corresponding to0,02 to0,25mg/l in a100ml aliquot portion of the undi
28、luted sample; Titrimetric method using the Tyndall effect: applicable when the absorption solution contains0,005mg of cyanide, corresponding to0,05mg/l in a100ml aliquot portion of the undiluted sample; Titrimetric method using an indicator, applicable when the absorption solution contains0,05mg of
29、cyanide, corresponding to0,5mg/l in a100ml aliquot portion of the undiluted sample. A large number of ions and compounds interfere with the determination. These are listed in the Table 1, together with the concentrations below which they do not interfere (the list is not exhaustive). If present sing
30、ly or in combination, up to the limiting concentrations, they do not interfere with the separation of hydrogen cyanide. The presence of aldehydes, e.g.formaldehyde, causes low cyanide values because of the formation of cyanohydrin. If any of the limiting concentrations of the interferences is likely
31、 to be exceeded, the sample shall be diluted with distilled water before stabilization (see clause6).BS 6068-2.17:1986 2 BSI 06-1999 Other interference may arise from the presence of fatty acids, which will distil and form soaps during titration of alkaline solution, and from the presence of element
32、ary sulfur. 2 Definition For the purpose of this Section of this British Standard the following definition applies. total cyanide simple and complex bound cyanides including organic compounds containing cyanogen groups forming hydrogen cyanide under the conditions of this method. Cyanohydrins are de
33、tected in part. CN-groups of compounds defined as such may partly or completely form cyanide ions or hydrocyanic acid respectively in water. Mononitriles (R-CN), cyanate and thiocyanate ions and cyanogen chloride are not included Table 1 Interferences Interference Limiting concentration, mg/l Sulfid
34、e 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 Silver ions Mercury ions Chromate ions Propionic acid Phenol Anthracene Naphthalene Anisaldehyde Piperon
35、al Pyrrole Pyridine Chlorine (elemental) Hydrogen peroxide Perborate ions 1000 500 1000 500 1000 1000 1000 1000 500 500 2000 5000 50 50 300 1000 1000 100 100 10 10 100 10 250 10 10BS 6068-2.17:1986 BSI 06-1998 3 Subsection 1. Liberation and absorption of hydrogen cyanide 3 Principle Heating the samp
36、le with hydrochloric acid in the presence of copper(I) ions. Entrainment of the liberated hydrogen cyanide in a current of air into an absorption vessel containing sodium hydroxide solution. NOTE 1Complex cobalt cyanides will not be determined quantitatively, because, according to their concentratio
37、ns, they are decomposed to the extent of between5 and15% only, this also applies to some organocyanide compounds. NOTE 2The effect of the specified digestion procedure on cyanohydrine is not fully characterized. 4 Reagents All reagents shall be of recognized analytical grade and the water used shall
38、 be distilled or deionized water. 4.1 Hydrochloric acid, solution,A 1,12g/ml. 4.2 Hydrochloric acid, solution, c(HCl)=1mol/l. 4.3 Sodium hydroxide, solution, c(NaOH)=1mol/l. 4.4 Sodium hydroxide, solution, c(NaOH)=5mol/l. 4.5 Tin(II) chloride, solution 1) Dissolve50g of tin(II) chloride dihydrate (S
39、nCl 2 .2H 2 O) in40ml of the hydrochloric acid solution(4.2) and dilute with water to100ml. Prepare a fresh solution each week. 4.6 Phenolphthalein, solution, containing chloroform. Dissolve0,03g of phenolphthalein in90ml of ethanol and add10ml of chloroform. 4.7 Zinc- and cadmium sulfate, solution.
40、 1) Dissolve100g of zinc sulfate heptahydrate (ZnSO 4 .7H 2 O) and100g of cadmium sulfate octahydrate(3Cd SO 4 .8H 2 O) in water and dilute with water to1000ml. 4.8 Copper(II) sulfate, solution. Dissolve200g of copper(II) sulfate pentahydrate (CuSO 4 .5H 2 O) in water and dilute with water to1000ml.
41、 4.9 Cadmium acetate, solution. 1) Dissolve300g of cadmium acetate dihydrate Cd(CH 3 COO) 2 .2H 2 O in water and dilute with water to1000ml. 4.10 Buffer solution, of pH5,4. Dissolve6g of sodium hydroxide (NaOH) in approximately50ml water, add11,8g of succinic acid (C 4 H 6 O 4 ) and dilute with wate
42、r to100ml. 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 Three-necked distillation flask, of capacity500ml, with standard
43、conical joints (centre neck29/32, side necks14,5/23). 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 capacity250ml, for purification of the air. 5.2 pH meter, with a glass electrode which will
44、 fit into the side necks of the distillation flask. 5.3 One-mark volumetric flasks, of capacities25,50,250 and1000ml. 6 Sampling and samples If the sample contains undissolved cyanides, it is necessary to ensure homogeneous distribution of the undissolved substances in the sample and its dilutions.
45、Immediately after sampling, add5ml of the sodium hydroxide solution(4.4),10ml of the phenolphthalein solution(4.6) and5ml of the tin(II) chloride solution(4.5) to each litre of sample or diluted sample. Adjust the pH to about8 by adding the hydrochloric acid solution(4.2), or the sodium hydroxide so
46、lution(4.3), drop by drop, until the water turns slightly red. Adjust the pH values of highly coloured samples in the same way after checking with the pH-meter(5.2) or with an indicator paper. Finally, add10ml of the zinc- and cadmium sulfate solution(4.7) to each litre of sample. Analyse the sample
47、 as soon as possible. If it is necessary to store it, keep it cool and in the dark. 1) SnCl 2is added as a reducing agent; zinc salt is added to provide stable zinc hexacyanoferrates, cadmium salts are added as sulfide acceptor and because of their bactericidal effect.BS 6068-2.17:1986 4 BSI 06-1999
48、 Figure 1 Apparatus for separation of hydrogen cyanide by strippingBS 6068-2.17:1986 BSI 06-1999 5 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
49、 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 losses of gaseous hydrogen cyanide due to disturbance of the equilibrium between the gaseous hydrogen cyanide and the hydrocyanic acid in the liquid phase of the pretreated sample. If the required volume of sample is already known before sampling, it is advisable to take only this volume and to carry out the determination on the whole sample. 7 Procedure 7.1 Liberation and
