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1、International Standard 670312 0 a 4 4! INTERNATlONACORGANlZATlON FOR STANOARDIZATlONW.4E)KLYHAPOHAR OPI-AHWALWR RO CTAHAAPTH3ALWWORGANlSATlON INTERNATIONALE DE NORMALISATION Water quality - Determination of cyanide - Part 2: Determination of easily liberatable cyanide Qualit de leau - Dosage des cya
2、nures - Partie 2: Dosage des cyanures aiskment libtkables First edition - 1964-09-01 UDC 543.2 : 546.267 Descriptors : water, quality, tests, determination, cyanides, water pollution. Ref. No. IS0 6703/2-1964 (E) Price based on 11 pages Foreword IS0 (the International Organization for Standardizatio
3、n) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Every member body interested in a subject for which a technical committee has been established has the right to be re
4、presented on that committee. International organizations, govern- mental and non-governmental, in liaison with ISO, also take part in the work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International
5、Standards by the IS0 Council. They are approved in accordance with IS0 procedures requiring at least 75 % approval by the member bodies voting. International Standard IS0 6703/2 was prepared by Technical Committee ISO/TC 147, Water quality. 0 International Organization for Standardization, 1994 0 Pr
6、inted in Switzerland ii Contents 0 Introduction 1 Scope and field of application . 2 Definition Section one: Liberation and absorption of hydrogen cyanide 3 Principle . 4 Reagents 5 Apparatus . . . 6 Sampling and samples . 7 Procedure Section two: Determination of cyanide ions - Photometric method w
7、ith pyridine/barbituric acid 6 Applicability 9 Principle . 10 Reagents r 11 Apparatus . 12 Procedure 13 Expression of results. 14 Precision . 15 Test report . Section three: Determination of cyanide ions - Titrimetric method using the Tyndall effect 16 Applicability. . 8 17 Principle and reactions .
8、 8 16 Reagents 8 19 Apparatus . 8 20 Procedure 9 21 Expression of results . 9 22 Precision . 9 23 Test report . 9 . . . III Section four: Determination of cyanide ions - Titrimetric method using an Indicator 24 Applicability 10 25 Principle . 10 26 Reagents 10 27 Apparatus . 10 ZB Procedure 10 29 Ex
9、pression of results . 10 30 Test report . 10 Bibliography . . . . . I.,., 11 iv -,-,- INTERNATIONAL STANDARD IS0 6703/2-1964 (E) Water quality - Determination of cyanide - Part 2: Determination of easily liberatable cyanide Attention is drawn to the toxicity of cyanide and to the need to fake extrem
10、e care when handling cyanides and their solu- tions. 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 samples and solutions containing cyanides or heavy metals in accordance with local official
11、regulations. Other chemicals specified in this part of IS0 6703 are also hazardous, for 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 cyan
12、ide. If cyanide compounds are chlorinated, cyanogen chloride (CICN) is produced, and this compound has to be determined separately. This International Standard comprises four parts as follows: Part 1 : Determination of total cyanide Part 2: Determination of easily liberatable cyanide Part 3: Determi
13、nation of cyanogen chloride Part 4: Determination of cyanide by diffusion at pH 61) The method described in parts 1, 2 and 3 are suitable for con- trolling the quality of water and for the examination of municipal sewage and industrial effluents. They are appropriate to the technology available for
14、the destruction of cyanides in treatment plants, and are based on the separation of liberated hydrogen cyanide (or in the case of IS0 670313, of cyanogen chloride) by stripping with a carrier gas. The method specified in part 4 is suitable for the determination of smaller amounts of cyanide, dependi
15、ng on the concentra- tions of copper and nickel. This part of IS0 6703 comprises four sections. Section one deals with the liberation and absorption of hydrogen cyanide. The other three sections deal with alternative methods for the quantitative determination of cyanide ions, as follows: - photometr
16、ic method with pyridine/barbituric acid (sec- tion two); - titrimetric method using the Tyndall effect (section three); - titrimetric method using an indicator (section four). 1) At present at the stage of draft, The specification of three alternative methods is necessary because each of the methods
17、 has its advantages and disadvan- tages. None can be quoted as applicable in all cases. The applicability of each method is described in clauses 8, 16 and 24. NOTE - Due to the different chemical behaviour of cyanide- containing or cyanide-producing substances, it is not possible to specify only one
18、 method for the quantitative determination of cyanide ions. 1 Scope and field of application This part of IS0 6703 specifies three methods for the deter- mination of easily liberatable cyanide (see clause 2) in water. The methods are applicable to water containing less than 56 mg of easily liberatab
19、le 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 dilu- tion of the sample. The methods and corresponding ranges of easily liberatable cyanide contents for which they are suitable are as
20、follows: - Photometric method with pyridine/barbituric acid: 0,002 to 0,025 mg of cyanide; - Titrimetric method using the Tyndall effect: 0,005 mg of cyanide; - Titrimetric method using an indicator: 0,05 mg of cyanide. A large number of ions and compounds interfere with the determination. These are
21、 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. -,-,- IS0 6703/2-1964 1 E) Table 1 - Interferences In
22、terference 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 and iron(lll) ions Copper ions Nickel(ll1 ions Silver ions Mercury ions Chromate ions Propionic acid Phenol An
23、thracene Naphthalene Anisaldehyde Piperonal Pyrrofe Pyridine Chlorine (elemental) Hydrogen peroxide Perborate ions Limiting concentration, mg/l 1000 xl0 loo0 500 1000 1000 loo0 1000 500 500 2ooo 5ooo IQ0 50 50 50 300 1000 1000 loo 100 10 10 100 10 250 10 10 If any of the limiting concentrations of t
24、he influences 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 %I, releasing hydro
25、cyanic acid 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. formaldeh
26、yde, may give lower cyanide values because of the formation of cyanohydrin. 2 Definition For the purpose of this International Standard, the following definition applies. easily liberatable cyanide: Cyanide from substances with cyanide groups and a measurable hydrocyanic acid vapour pressure at pH 4
27、 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 a
28、nd cyanogen chloride are not included. -,-,- IS0 6703/2-1964 (El Section one: Liberation and absorption of hydrogen cyanide 3 Principle Liberation of hydrogen cyanide from the sample by treatment at pH 4 with metallic zinc and EDTA. Entrainment of the hydrogen cyanide in a current of air into an abs
29、orption vessel containing sodium hydroxide solution. 4.8 Buffer solution, of pH 4,0. Dissolve 80 g of potassium hydrogen phthalate (CeHeKb4) in 920 ml of warm water. 4 Reagents All reagents shall be of recognized analytical grade and the water used shall be distilled or deionized water. 4.9 EDTA, so
30、lution. Dissolve 100 g of ethylenedinitrilotetraacetic acid, where m, is the cyanide content, in milligrams, of the test solu- tion read from the calibration curve; mb is the cyanide content, in milligrams, of the blank test solution; V, is the volume, in millilitres, of the test portion; f, = 0,4,
31、as only 40 % of the contents of the absorption vessel are taken for the determination; f2 = 0,97, as the volume of the sample is increased by the addition of preservatives immediately after sampling. This factor is lowered by 0,Ol for each 10 ml, if, during neutrali- zation, more than 10 ml of reage
32、nt were used for each litre of sample. Report results in milligrams per litre, taking into account the precision shown in table 2. 14 Precision The precision data shown in table 2 were obtained in inter- laboratory trials; the samples were taken from the ground water of a landfill area, 15 Test repo
33、rt The test report shall include the following information : a) the reference of the method used (i.e. IS0 6703/2, pho- tometric method); b) the results and the method of expression used; d) details of any operating procedures not specified in sec- tions one and two of this part of IS0 6703, or rega
34、rded as optional, together with any incidents likely to have affected the results. Table 2 - Precision data (photometric method) Sample Number of laboratories Cyanide content mgll Comparative variation coefficient % Potassium cyanide solution Stabilized sample Stabilized sample with addition of pota
35、ssium cyanide 16 0 6 16 0,13 31 16 0,32 22 -,-,- IS0 6703/2-1984 (E) Section three: Determination of cyanide ions - Titrimetric method using the Tyndall effect 16 Applicability This method may be applied to absorption solutions which con- fain more than 0,005 mg of cyanide. The method is not applica
36、ble if the absorption solution is tur- bid, although slightly turbid solutions may still be titrated. In many cases, highly turbid solutions can be “cleaned up” by shaking with 1 to 2 ml of carbon tetrachloride. Phase separa- tion may be accelerated by using a centrifuge. 17 Principle and reactions
37、Formation of complex silver cyanide ions in accordance with the equation : 2CN -I- Ag+ -AgfCN)z- which, in the presence of an excess of silver ions, results in the precipitation of silver cyanide: AgKN12 - + Age -t2AgCN The addition of potassium iodide improves detection of the end-point (as the sol
38、ubility product of silver iodide is lower than that of silver cyanide) : I- + Ag+ -t Agl The formation of colloidal silver iodide is indicated by the Tyndall effect. 18 Reagents All reagents shall be of recognized analytical grade and the water used shall be distilled or deionized water. 18.1 Silver
39、 nitrate, solution, c(AgNOs) = 0,Ol mol/l. 18.2 Silver nitrate, solution, c(AgNOsj = 0,001 mol/l. Store this solution, and the burette in which it is used, in the dark. Check the titre of the solution at frequent intervals or prepare a fresh solution prior to each use from the silver nitrate solutio
40、n (18.1). 18.3 Potassium iodide, solution. Dissolve 20 g of potassium iodide in water and dilute with water to 100 ml. 19 Apparatus (see figure 2) Usual laboratory equipment, and 19.1 Automatic (dark glass) burette, of capacity 10 ml, capable of measuring volumes to an accuracy of better than 0,005
41、ml, or, if an automatic burette is not available, a microburette. 19.2 Magnetic stirrer with a black platform and black stirring bar. 19.3 High intensity light source, for example a microscope lamp with an adjustable focussing lens and a diaphragm, or a slide projector with a diaphragm or a double-b
42、eam lamp with fibre-optics system. The diameter of the aperture shall be 4 to 6 mm. 19.4 Titration vessels, made of glass, unmarked, of internal diameter about 25 mm and capacity 20 ml. Burette Yl FL- Diaphragm 7 I I - - - -lll:$z,- I l- Magnetic Magnetic stirrer stirrer k-r I I Figure 2 - Figure 2
43、- Apparatus for determination of cyanide ions using Tyndall effect Apparatus for determination of cyanide ions using Tyndall effect - - - -,-,- IS0 6703/2-1664 (EI 20 Procedure where Transfer the contents of the absorption vessel into a 25 ml one- markvolumetric flask. Rinse fhe vessel three times w
44、ith approx- imately 3 ml portions of water, transfer the rinsings to the flask, dilute to the mark with water and mix. V. is the total volume, in millilitres, of silver nitrate solu- tion (18.2) required for the two titrations in the blank test; VI is the volume, in millilitres, of silver nitrate so
45、lution (18.2) required for the first titration; The titration should preferably be performed in a darkened room. V2 is the volume, in millilitres, of silver nitrate solution (18.2) required for the second titration; Place the volumetric flask in the light beam (see figure 2). If the solution is turb
46、id, see clause 16. If a Tyndall effect is not clearly visible, transfer, by means of a pipette, two 10 ml aliquot por- tions of the solution to two titration vessels (19.4) and add 1 drop of the potassium iodide solution (18.3) to each. V, is the volume, in millilitres, of the sample; f, = 0,052, i.
47、e. the mass, in milligrams, of CN- equivalent to 1 ml of 0,001 mol/l silver nitrate solution; Place one titration vessel on the magnetic stirrer and add the stirring bar. Place the other vessel between the first one and the light source (see figure 2). If a double-beam lamp is used, place the vessel
48、s side by side. Immerse the tip of the burette contain- ing the silver nitrate solution (18.2) in the solution, switch on the magnetic stirrer and start the titration. Titrate slowly because the formation of silver iodide is slow. f2 = 0,8, as only 80 % of the contents of the absorption vessel are t
49、aken for titration; f3 = 0,97, as the volume of the sample is increased by the addition of preservatives immediately after sampling. This factor is lowered by 0,Ol for each 10 ml, if, during neutralization, more than 10 ml of reagent were used for each litre of sample. The end-point is reached when the turbidity caused by the Tyndall effe