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 + 663.63:53/54BS6068-2.18:1986 This British Standard, having been prepared under the directionof t
2、he Environment andPollution Standards Committee, was published underthe authority of the Board ofBSI and comes into effect on 28February1986 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference EPC/44 Draft for comment 82/56062 DC ISBN 0 580 14988 9 Amend
3、ments issued since publication Amd. No. Date of issue CommentsBS6068-2.18:1986 BSI 10-1999 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 an
4、d samples 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 Ti
5、trimetric method using the Tyndall effect 16 Applicability 8 17 Principle and reactions 8 18 Reagents 8 19 Apparatus 8 20 Procedure 9 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 Pr
6、inciple 11 26 Reagents 11 27 Apparatus 11 28 Procedure 11 29 Expression of results 11 30 Test report 11 Figure 1 Apparatus for separation of hydrogen cyanide by stripping 4 Figure 2 Apparatus for determination of cyanide ions using Tyndalleffect 8 Table 1 Interference 2 Table 2 Precision data (photo
7、metric method) 7 Table 3 Precision data (titrimetric method) 10 Bibliography 12 Publications referred to Inside back coverBS6068-2.18:1986 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,
8、is based on ISO 6703-2:1984 “Water quality Determination of cyanide Part2: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
9、International Organization for Standardization (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
10、 incorporated are that the text has been 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 hydrox
11、ide solution. This British Standard 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 Parts 1 to 6, which, together with Part0, are listed below. Part 0: Introduction; Pa
12、rt 1: Glossary; Part 2: Physical, chemical 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 w
13、ith those used in British Standards; 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” f
14、or litre (and its submultiples) rather 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
15、observed. This is known as the Tyndall 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 obligat
16、ions. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 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
17、 inside front cover.BS6068-2.18:1986 BSI 10-1999 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 pip
18、ette (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 example pyridine. 0 Introduction Cyanides may be present in water as hyd
19、rocyanic 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 this compound has to be determined separately. There are 4 Sections in BS 6
20、068 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 determination of cyanogen chloride. BS 6068-2.20:1986, Method for determ
21、ination of cyanide by diffusion at pH 6. The methods described in Sections 2.17, 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 tr
22、eatment 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 separation, is suitable for the determination of smaller amounts of cyanide, dep
23、ending 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 alternative methods for the quantitative determination of cyanide ions, as fo
24、llows: 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 methods is necessary because each of the methods has its advantages and dis
25、advantages. 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 substances, it is not possible to specify only one method for the quantitative dete
26、rmination 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 to water containing less than 50mg of easily liberatable cyanide (as cyani
27、de ions) per litre, and less than 100mg 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 cyanide contents for which they are suitable are as follows: Photometric me
28、thod with pyridine/barbituric acid: applicable when the absorption solution contains 0,002to0,025mg of cyanide, corresponding to 0,02to0,25mg/l in a 100ml aliquot portion of the undiluted sample; Titrimetric method using the Tyndall effect: applicable when the absorption solution contains0,005mg of
29、cyanide, corresponding to 0,05mg/l in a 100ml aliquot portion of the undiluted sample; Titrimetric method using an indicator: applicable when the absorption solution contains 0,05mg of cyanide, corresponding to0,5mg/l in a 100ml aliquote portion of the undiluted sample. A large number of ions and co
30、mpounds 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, they do not interfere with the separation of hydrogen cyanide. The list is not exhaustive.BS6
31、068-2.18:1986 2 BSI 10-1999 Table 1 Interferences If any of the limiting concentrations of the influences are likely to be exceeded, dilute the sample with distilled water before stabilization (seeclause6). Prussiates (pentacyano complexes with iron), which cannot be destroyed by chlorination under
32、normal conditions of waste water treatment, partly decompose (up to 50%), releasing hydrocyanic acid under the conditions specified. If it is desired to exclude prussiates, the procedure specified in clause6 and 7.1 has to be used. This procedure is only applicable, however, if the concentration of
33、copper ions in the sample is less than 1mg/l. The presence of aldehydes, e.g. formaldehyde, may 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 cyanid
34、e from substances with cyanide groups and a measurable hydrocyanic acid vapour pressure at pH4 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, silve
35、r, copper and nickel. Complex cyanides of iron and cobalt, nitriles, cyanates, thiocyanates and cyanogen chloride are not included Interference Limiting concentration, mg/l Sulfide ions Polysulfide ions Sulfide and polysulfide ions Sulfide ions Thiosulfate ions Thiocyanate ions Carbonate ions Cyanat
36、e ions Nitrate ions Nitrite ions Ammonium ions Iron(II) and iron(III) ions Copper(II) ions Nickel(II) ions Silver ions Mercury ions Chromate ions Propionic acid Phenol Anthracene Naphthalene Anisaldehyde Piperonal Pyrrole Pyridine Chlorine (elemental) Hydrogen peroxide Perborate ions 1000 500 1000 5
37、00 1000 1000 1000 1000 500 500 2000 5000 100 50 50 50 300 1000 1000 100 100 10 10 100 10 250 10 10BS6068-2.18:1986 BSI 10-1999 3 Subsection 1. Liberation and absorption of hydrogen cyanide 3 Principle Liberation of hydrogen cyanide from the sample by treatment at pH4 with metallic zinc and EDTA. Ent
38、rainment 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 g/ml. 4.2 Hydrochloric
39、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 50g of tin(II) chloride dihydrate (SnCl 2 .2H 2 O) in 40ml of the hydrochloric acid solution (4.2) and dilute with water to
40、 100ml. Prepare a fresh solution each week. 4.6 Phenolphthalein, solution, containing chloroform. Dissolve 0,03g of phenolphthalein in 90ml of ethanol and add 10ml of chloroform. 4.7 Zinc- and cadmium sulfate, solution. 1) Dissolve 100g of zinc sulfate heptahydrate (ZnSO 4 .7H 2 O) and 100g of cadmi
41、um sulfate octahydrate (3CdSO 4 .8H 2 O) in water and dilute with water to 1000ml. 4.8 Buffer solution, of pH 4,0. Dissolve 80g of potassium hydrogen phthalate (C 8 H 5 KO 4 ) in 920ml of warm water. 4.9 EDTA, solution. Dissolve 100g of ethylenedinitrilotetraacetic acid, disodium salt dihydrate (C 1
42、0 H 14 N 2 Na 2 O 8 .2H 2 O) in940ml 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 Three-neck
43、ed distillation flask, of capacity500ml, 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 250ml, for purification o
44、f 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 capacities25,50,250 and 1000ml. 6 Sampling and samples 6.1 If the sample contains undissolved cyanides, it is necessary to ensure homogeneous distribution
45、of the undissolved substances in the sample and its dilutions. Immediately after sampling, add 5ml of the sodium hydroxide solution (4.4), 10ml of the phenolphthalein solution (4.6) and 5ml of the tin(II) chloride solution (4.5) to each litre of sample or diluted sample. Adjust the pH to about 8 by
46、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 10ml of the zinc- and
47、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
48、 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 losses of gaseous hydrogen cyanide due to disturbance of the equilibrium between the ga
49、seous 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. 6.2 If prussiates are to be excluded from the determination, adjust the amount of tin(II) chloride solution (4.5) added so as to correspond to the content of oxidizing agents. The excess of tin(II) chloride solution shall be limited to 0,1ml for each sample. 1) Zinc salt is
