BS-6068-2.20-1986 ISO-6703-4-1985.pdf

BRITISH STANDARD BS 6068-2.20: 1986 ISO 6703-4: 1985 Water quality Part 2: Physical, chemical and biochemical methods Section 2.20 Method for determination of cyanide by diffusion at pH 6 ISO title: Water quality Determination of cyanide Part 4: Determination of cyanide by diffusion at pH 6 UDC 556.11 + 614.777 + 628.1/.3 + 663.63:53/54 Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.20:1986 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 relate to the work on this standard: Committee reference EPC/44 Draft for comment 83/55540 DC ISBN 0 580 14986 2 Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.20:1986 © BSI 10-1999i Contents Page National forewordii 0Introduction1 1Scope and field of application1 2Definition1 3Principle1 4Reagents1 5Apparatus2 6Sampling and samples3 7Procedure3 8Expression of results4 9Interferences5 10Test report5 Figure Microdiffusion cell6 Table Determination of known amounts of cyanide4 Publication referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.20:1986 ii © BSI 10-1999 National foreword This Section of this British Standard, which has been prepared under the direction of the Environment and Pollution Standards Committee, is identical with ISO 6703-4:1985 “Water quality Determination of cyanide Part 4: Determination of cyanide by diffusion at pH 6”. The International Standard was prepared by subcommittee 2, Physical, chemical and biochemical methods, of Technical Committee 147, Water quality, of the International Organization for Standardization (ISO) as a result of discussion in which the UK participated. 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 Part 0, are listed below. Part 0: Introduction; Part 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. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with 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. Wherever the words “International Standard” or “part of ISO 6703” appear, referring to this standard, they should be read as “British Standard” or “Section of BS 6068” respectively. In British Standards it is current practice to use the symbol “L” for litre (and its submultiples) rather than “l” and to use the spelling “sulphur”, etc., instead of “sulfur”, etc. ISO 6703-1:1984 and ISO 6703-2:1984 are referred to in clause 0 for information only. Accordingly, the validity of this standard is not affected. British Standards related to ISO 6703-1 and ISO 6703-2 are BS 6068-2.17 and BS 6068-2.18 respectively. Textual errors. When adopting the text of the International Standard, the following textual errors were discovered. They have been marked in the text and have been reported to ISO in a proposal to amend the text of the International Standard. a) In clause 1, line 1, the word “detemination” should read “determination”. b) In 4.7.2, paragraph 2, the last sentence should read “Standardize the solution immediately before use or daily, if many determinations are carried out on a single day, as follows.” Cross-references International StandardCorresponding British Standard BS 6068 Water quality: Part 2 Physical, chemical and biochemical methods ISO 6703-3:1984Section 2.19:1986 Method for determination of cyanogen chloride (Identical) Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.20:1986 © BSI 10-1999iii Additional information a) The carrier gas referred to in the last line of clause 0, paragraph 3, is air. b) It is difficult to stir solutions in volumetric flasks and dissolution of the sodium hydroxide referred to in 4.1 may be facilitated by shaking the flask or swirling the contents of the flask. c) It is understood that in 8.2, the term “type II reagent water” refers to distilled water, and “water of choice” and “selected water media” are various samples of water of USA origin. 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 samples and solutions containing cyanides in accordance with local official regulations. Other chemicals specified in this part of ISO 6703 are also hazardous, for example pyridine. 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 comprises a front cover, an inside front cover, pages i to iv, pages 1 to 6, 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: sheffieldun sheffieldun, na, Tue Dec 05 01:28:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.20:1986 © BSI 10-19991 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 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: Determination of cyanogen chloride; Part 4: Determination of cyanide by diffusion at pH 6. The methods described in parts 1, 2 and 3 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 separation of liberated hydrogen cyanide (or in the case of ISO 6703-3, of cyanogen chloride1) by stripping with a carrier gas. The method specified in part 4 is suitable for the determination of smaller amounts of cyanide. In the presence of large amounts of copper and nickel, this method will not give quantitative results. 1 Scope and field of application This part of ISO 6703 specifies a method for the detemination2) of free cyanide (see clause 2) in photographic effluents and wastewaters. The method is applicable to water containing from 10 to 150 4g of free cyanide per litre, but higher concentrations may be determined by suitable dilution of the sample. The response is linear over the range indicated. For possible interferences, see clause 9. NOTE 1The given test procedure is sophisticated and calls for care in sample storage and manipulation of the samples and equipment. The method requires practice and manual dexterity. NOTE 2It is not the purpose of this part of ISO 6703 to specify the measurement of the amount of potentially available cyanide, but rather the amount being already present and determinable by this method (see clause 2). 2 Definition For the purpose of this part of ISO 6703, the following definition applies. cyanide under the conditions of this method, liberatable cyanide which diffuses as hydrogen cyanide (HCN) at room temperature from a solution at pH 6, including simple compounds of cyanide and its easily dissociated complexes. It does not include complexes that resist dissociation, such as iron cyanide and gold cyanide, although these chemical species can, under appropriate conditions such as heat and radiant energy, form cyanide 3 Principle Transfer of a test portion to a microdiffusion cell and treatment with cadmium ions to precipitate cyanoferrates. Buffering of the solution to pH 6, and diffusion of the hydrogen cyanide produced into a sodium hydroxide absorber solution. Treatment of this test solution with chloramine-T, and reaction of the cyanogen chloride (CICN) formed with barbituric acid in pyridine to form a coloured complex. Measurement of the absorbance of this complex at 580 nm, which is directly related to the amount of cyanide in the test portion. 4 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Sodium hydroxide, 0,1 mol/l solution. Add 4,0 g of sodium hydroxide to 800 ml water in a 1 000 ml one-mark volumetric flask. 1)Stir until dissolved, cool the solution to room temperature, and make up to the mark with water. 4.2 Sodium hydroxide, 0,05 mol/l solution. Dilute one part by volume of sodium hydroxide solution (4.1) with one part by volume of water. 4.3 Potassium dihydrogenphosphate (KH2PO4), 190 g/l solution. Add, to 150 ml sodium hydroxide solution (Õ = 100 g/l), 190 g potassium dihydrogenphosphate in a 2 l beaker. Add water to 800 ml to aid dissolution. Adjust the solution to pH 5,9 to 6,1 using the same sodium hydroxide solution. Transfer the solution to a 1 000 ml volumetric flask and make up to the mark with water. 1) See national foreword (Additional information). 2) For details of textual error see national foreword. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.20:1986 2 © BSI 10-1999 4.4 Cadmium chloride (CdCl2), 10 g/l solution. Dissolve 10,0 g of anhydrous cadmium chloride in about 200 ml of water in a 1 000 ml one-mark volumetric flask and make up to the mark with water. 4.5 Chloramine-T (C7H7CINNa2O2S.3H2O),3) 10 g/l solution. Dissolve 1,0 g of chloramine-T in 50 ml water in a 100 ml one-mark volumetric flask, and make up to the mark with water. This reagent should be prepared daily. 4.6 Pyridine-barbituric acid, solution. Add 3,0 g barbituric acid trihydrate (C4H4N2O3.3H2O) to a 50 ml one-mark volumetric flask. Wash down the sides of the flask with just enough water to moisten the barbituric acid. Add 15 ml pyridine (C5H5N) and swirl to mix. Add 3 ml hydrochloric acid, Õ = 1,12 g/ml, and make up 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 1 day if stored in the dark at room temperature, and for 1 week if stored under refrigeration. NOTEThe optimum wavelength for absorbance measurements may vary due to impurities in various batches of barbituric acid (see 7.3.3). 4.7 Cyanide, standard solution corresponding to about 2 mg of CN per litre. 4.7.1 Silver nitrate (AgNO3), standard solution, 0,02 mol/l. Dissolve 3,397 g silver nitrate in water in a 1 000 ml one-mark volumetric flask and make up to the mark with water. Store in an amber glass bottle. 4.7.2 Cyanide, stock solution, Õ(CN ) . 1,0 g/l Dissolve 2,5 g potassium cyanide in 500 ml sodium hydroxide solution (4.2) in a 1 000 ml one-mark volumetric flask, and make up to the mark with sodium hydroxide solution (4.2). Standardization of the cyanide stock solution is carried out by potentiometric titration with silver nitrate to form silver cyanide as follows. Standardize the solution periodically or before use, as appropriate.4) Transfer 20,0 ml of the stock solution to a glass beaker on a magnetic stirring apparatus. Immerse the electrodes 5.6 and 5.7, appropriately connected to the pH meter (5.8) in the solution, turn on the stirrer, and add silver nitrate solution (4.7.1) in small increments from a burette. Record the potential indicated by the pH meter after each increment, then plot these potentials against the volume of silver nitrate added, producing a sharp bend near the equivalence point. The end-point of the titration is at the intersection of the vertical and horizontal parts of the titration curve, and 1 ml of silver nitrate solution is equivalent to 1,04 mg of cyanide. Alternative methods for standardization may be used. 4.7.3 Cyanide, standard solution. In a 1 000 ml volumetric flask, place a volume of 100 ml of cyanide stock solution (4.7.2). Make up to the mark with sodium hydroxide solution (4.2). Dilute in the same way a volume of 20 ml of the solution thus obtained to 1 000 ml. After the second dilution, the final concentration is about 2 mg/l. The exact value is derived from the value found in the standardization of the stock solution. Prepare both solutions daily or as required. 1 ml of this standard solution contains about 2 4g of CN . 4.8 Phosphoric acid-dihydrogenphosphate, buffer solution. Add 8,0 ml phosphoric acid, Õ = 1,70 g/ml, to 100 ml of potassium dihydrogenphosphate solution (4.3). 4.9 Petroleum jelly 5 Apparatus Usual laboratory equipment, and 5.1 Diffusion cell, of glass or porcelain, for example see the Figure. The cell shall be fitted with a glass cover-plate with one surface ground, capable of achieving an airtight seal. 5.2 Micropipettes or calibrated syringes, to deliver 0,10, 0,50; or 1,00 ml. 5.3 Spectrometer, fitted with tungsten lamp, suitable for measurements between 570 and 594 nm, and equipped with optical cells of thickness 10 mm with watertight stoppers. NOTEOptical cells of different thicknesses may be used. 5.4 Adjustable pipette or syringe, to deliver 1,30 ml. 5.5 Calomel reference electrode, with saturated KNO3 electrolyte, or equivalent. 5.6 Silver electrode 5.7 pH meter, with millivolt scale. 3) N-chloro-4-toluenesulfonamide, sodium salt trihydrate. 4) For details of textual error see national foreword. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 01:28:13 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.20:1986 © BSI 10-19993 6 Sampling and samples Immediately after sampling, laboratory samples shall be adjusted with sodium hydroxide solution (4.1) to above pH 10 for preservation. Samples should be analysed as quickly as