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1、International Standard f 6703 /3 0 * 8 4iii INTERNATIONAL ORGANIZATION FORSTANOARDltATlONMYAPOHAR OPrAHH3AUMA I-IO CTAHIIAPTH3AUHM-ORGANlSATlON INTERNATIONALEDE NORMALISATION Water quality - Determination of cyanide - Part 3: Determination of cyanogen chloride Qualite de l eau - Dosage des cyanures
2、- Partie 3: Dosage du chforure de cyanoggne First edition - 1994-09-01 UDC 643.2 : 646.267 Descriptors : water, quality, tests, determination, cyanides, water pollution. Ref. No. IS0 6703/3-1964 (E) Price based on 6 pages Foreword IS0 (the International Organization for Standardization) is a worldwi
3、de 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 represented on th
4、at 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 Standards by th
5、e IS0 Council. They are approved in accordance with IS0 procedures requiring at least 75 % approval by the member bodies voting. International Standard IS0 6703/3 was prepared by Technical Committee ISO/TC 147, Water quality. 0 International Organization for Standardization, 1984 l Printed in Switze
6、rland INTERNATIONAL STANDARD IS0 6703/3-1964 (E) Water quality - Determination of cyanide - Part 3: Determination of cyanogen chloride Attention is drawn to the toxicity of cyanide and to the need to take extreme care when handling cyanides and their solu- tions. Carry out all operations in a fume c
7、upboard. 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 regulations. Other chemicals specified in this part of IS0 6703 are also hazardous, for e
8、xample 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 this
9、 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 Pat-t 3: Determination of cyanogen chloride Part 4: Determination of cyanide by diffusion at pH 61) The
10、methods 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 the destruction of cyanides in treatment plants, and are based on the separation of li
11、berated hydrogen cyanide (or in the case of this part of IS0 6703, 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, depending on the concentra- tions of copper and nickel. 1 Scope and field of appli
12、cation This part of IS0 6703 specifies a method for the determination of cyanides, as cyanogen chloride (see clause 2) in water. The method is applicable for the determination of cyanogen chloride concentrations in the range 0,02 to 15 mg/l. 1) At present at the stage of draft. The ions and compound
13、s listed in the table, if present singly or in combination at concentrations above the specified limiting concentration, interfere with the method (the list is not ex- haustive). The presence of aldehydes, e.g. formaldehyde, may give lower cyanide values because of the formation of cyanohydrin, Tabl
14、e - Interferences Interference Limiting concentration mg/l 2 Definition For the purpose of this International Standard, the following definition applies : cyanogen chloride: The first reaction product when cyanide compounds are chlorinated. Cyanogen chloride is a gas and is only slightly soluble in
15、water, but is highly toxic even in low concentrations. 3 Principle Addition of tin (II) chloride solution to the sample and entrain- ment of the cyanogen chloride liberated at pH 54 and room temperature by means of a current of air into an absorption solution containing pyridine/barbituric acid. Det
16、ermination of the cyanogen chloride concentration photometrically. IS0 6703/3-1964 (El 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, Q 1,12 g/ml. 4.2 Hydrochloric acid, solution, c(HCI) = 1 m
17、ol/l. 4.3 lIn(llI chloride, solution. Dissolve 50 g of tin (II) chloride dihydrate (SnClz -2HzO) in the hydrochloric acid solution (4.21 and dilute with the same hydrochloric solution to 1 000 ml. Prepare a fresh solution each week. 4.4 Sodium chloride, solution, c(NaCI) = 0,5 mol/l. 43 Sodium hydro
18、xide, solution, c(NaOH) = 0,4 mol/l. 4.6 Pyrldine/barbituric acid, solution. Place 3 g of barbituric acid (C4H4N203) in a 50 ml one-mark volumetric flask, wash down the walls of the flask with just enough water to moisten the barbituric acid, add 15 ml of pyridine (CsHsN), and swirl to mix. Add 3 ml
19、 of the hydrochloric acid solution (4.1) and dilute to the mark with water. Store overnight in a refrigerator and, if necessary, filter to eliminate any undissolved barbituric acid. The solution is stable for I day if stored in the dark and for 1 week if stored in a refrigerator. 4.7 Potassium cyani
20、de, standard solution corresponding to 10 mg of CN- per litre. Dissolve 25 mg of potassium cyanide in the sodium hydroxide solution (4.5) and dilute with the same sodium hydroxide solu- tion to 1 600 ml in a one-mark volumetric flask. Standardize this solution by titration with the silver nitrate so
21、lu- tion (4.8), immediately before use or once each day, if numerous determinations are carried out. 4.6 Silver nltrate, solution, c(AgNOs) = 0,Ol mol/i. Store in a dark bottle. 4.9 Buffer solution, of pH 5,4. Dissolve 6 g of sodium hydroxide in approximately 50 ml of water, add II,8 g of succinic a
22、cid (C4HsD4) and dilute with water to 100 ml. 4,lO Chloramine-T, solution. Dissolve 0,5 g of chloramine-T trihydrate (C7H7CINaNS0z3H20) in water in a 50 ml one-mark volumetric flask and dilute to the mark with water. Prepare fresh solution each week. Check each batch of chloramine-T against a calibr
23、ation curve. 5 Apparatus Usual laboratory equipment, and 5.1 Three-necked distillation flask, of capacity 560 ml, with standard conical joints (centre neck 29/32, side necks 14,5/23) and funnel, as shown in figure 1). 5.2 Absorption vessel, protected against return, with frit- ted glass Gl (see figu
24、re 2). 5.3 54 5.5 5.6 Separating funnell), of capacity 106 ml (see figure 3). Sampling funnell), of capacity 10 ml (see figure 4). Sampling funnell), of capacity 1 ml (see figure 5). Volumetric flasks, of capacities 25, 50, 250 and 1 000 ml. 5.7 Flowmeter. 5.6 Spectrometer, with cells of optical pat
25、h length 10 mm. 6 Sampling and samples For expected cyanogen chloride concentrations of less than 0,15 mg/l, collect the sample in the separating funnel (5.3). For expected concentrations between 0,15 and 1,5 mg/l, collect the sample in the IO ml sampling funnel (5.4) and for expected concentrations
26、 between I,5 and 15 mg/l, collect the sample in the 1 ml sampling funnel (5.5). Take the samples by immersing the appropriate funnels in the water to be sampled (with the stop-cocks closed below the sur- face of the water). If using the separating funnel (5.3), place 5 ml of the tin (II) chloride so
27、lution (4.3) in it before collecting the sample. Stopper the funnel immediately. If one of the sampling funnels (5.4 or 5.5) was used to collect the sample, place 5 ml of the tin(ll) chloride solution (4.3) in the separating funnel (5.3) and dilute with water to 100 ml. Rinse the sampling funnel (5.
28、4 or 5.5) with water and place it on the separating funnel (5.3). Open the stop-cock of the separating funnel first, then the lower, and finally the upper, stop-cock of the sampling funnel. After about 20 ml have run out of the separating funnel, close the stop-cocks of the separating funnel, remove
29、 the sampling funnel and stopper the separating funnel immediately. Analyse as soon as possible and in any case within 24 h. If it is necessary to store the sample keep it cool and in the dark. 1) The exact volumes of the separating (5.3) and sampling funnels (5.4 and 5.5) should be determined prior
30、 to use. 2 -,-,- IS0 6703/3-19 it is stable for several days at room temperature.) Connect the absorption vessel to the pump and adjust the air flow to about 40 I/h. Place the separating funnel (5.3) in one side neck and the other funnel (5.4 or 5.5) in the second side neck. Pour 10 ml of the buffer
31、 solution (4.9) into the flask. Open the stop-cock of the separating funnel and lift the stopper carefully to allow air to enter. When the separating funnel is empty, remove the stopper and rinse the funnel with a small amount of water. After 1 min, close the stop-cock of the separating funnel, so t
32、hat the air stream enters the flask through the other funnel. After 20 min, disconnect the air supply. Transfer the contents of the absorption vessel into a volumetric flask, rinse the vessel with a very small amount of water, dilute to the mark and mix. 7.2 Blank test Measure the absorbance of each
33、 solution at 578 nm in a cell of optical path length 10 mm against a reference solution.ll Carry out the measurements 20 f 5 min after addition of the pyridine/barbituric acid solution. 7.4.3 Plotting the graph Plot a graph of absorbance against the cyanide contents, in milligrams, of the solutions.
34、 The relationship between absor- bance and concentration is linear. Check the graph from time to time, especially if new batches of chemicals are used. Check the absolute values of the calibration graph by titration of the calibration standard with silver nitrate solution. 8 Expression of results Th
35、e cyanogen chloride concentration, expressed in milligrams per litre, is given by the formula 2,36 x m x 1 000 V where m is the cyanide content, in milligrams, read from the calibration curve; Carry out a blank test in parallel with the determination, using the same reagents in the same quantities a
36、nd following the same procedure, but replacing the test sample with water. V is the volume, in millilitres, of the sample; 2,36 is the conversion factor to express cyanide as cyanogen chloride. 7.3 Determination Immediately (not later than 10 min) after separation of the cyanogen chloride, measure t
37、he absorbance of the absorption solution at 578 nm, using the blank test solution (7.2) as the reference liquid. Report results in milligrams per litre. 9 Precision This method is not suitable for inter-laboratory testing because stable solutions of cyanogen chloride cannot be prepared and 7.4 Prepa
38、ration of calibration graph distributed. 7.4.1 Preparation of standard matching solutions 10 Test report Transfer, by means of a pipette, 2,5,20 and 25 ml, respective- ly, of the standard potassium cyanide solution (4.7) into a series of four 250 ml one-mark volumetric flasks (5.6). Dilute to the ma
39、rk with the sodium hydroxide solution (4.5) and mix. Transfer, by means of a pipette, 10 ml of each of these solu- tions into 25 ml one-mark volumetric flasks (5.6) and add, whilst mixing, 2 ml of the buffer solution (4.91, 4 ml of the hydrochloric acid solution (4.2) and 1 ml of the chloramine-T so
40、lution (4.10). Stopper the flasks and leave for 5 ?X 1 min. Add 3 ml of the pyridine/barbituric acid solution (4.61, dilute to the mark with water and mix. The test report shall include the following information : a) reference to this part of IS0 6703; b) the results and the method of expression use
41、d; C) any unusual features noticed during the determination; d) details of any operating procedures not specified in sections one and three of this part of IS0 6703, or regarded as optional, together with any incidents likely to have af- fected the results. 1) Prepare this reference solution using 10 ml of the sodium hydroxide solution (4.5) instead of the stripping solution. 5 -,-,- IS0 6703/3-1964 (El Bibliography MERTENS, H., Z.f. Wasser und Abwasser-Forschung, 9 (19761, pp. 163-195. MERTENS, H., Vom Wasser, 52 (19791, pp. 61-74. -,-,-