1、BRITISH STANDARD BS2690-15: 1974 Methods of testing Water used in industry Part 15: Free EDTA, total salts of EDTA, polyacrylate and polymethacrylate UDC 628.1:663.63.01:543.3BS2690-15:1974 This British Standard, having been endorsed by the Chairmanofthe Chemical Divisional Council, was publishedund
2、er the authorityofthe Executive Boardon 31 July1974 BSI 08-1999 Part 15 first published July 1974 The following BSI references relate to the work on this standard: Committee reference C/37 and C/37/1 Draft for comment73/51750 ISBN 0 580 08116 8 Co-operating organizations The Technical Committee whic
3、h has been working under the supervision of the Chemical Divisional Council, and which is responsible for the preparation of this British Standard, consists of representatives from the following Government departments and scientific and industrial organizations: Association of Shell Boiler Makers Br
4、itish Launderers Research Association British Steel Industry Chemical Industries Association Department of Employment (HM Factory Inspectorate) Department of Trade and Industry, Laboratory of the Government Chemist Electricity Supply Industry in England and Wales Institute of Fuel Institute of Marin
5、e Engineers Institution of Chemical Engineers Institution of Corrosion Technology Institution of Gas Engineers Institution of Mechanical Engineers London Transport Executive Ministry of Defence, Navy Department National Coal Board Society of Laundry Engineers and Allied Trades Ltd Society for Water
6、Treatment and Examination Individual manufacturers Amendments issued since publication Amd. No. Date of issue CommentsBS2690-15:1974 BSI 08-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 General 1 2 Definitions 1 3 Free EDTA 1 4 Total salts of EDTA 2 5 Polyacrylate
7、and polymethacrylate 4 Publications referred to Inside back coverBS2690-15:1974 ii BSI 08-1999 Foreword This British Standard has been prepared under the authority of the Chemical Divisional Council. Since the original publication of BS2690 in1956, an addendum was published in1960 extending the meth
8、ods to cover the testing of very pure waters. Since that time, various further advances have been made in the development of methods of analysing water and the standard has been revised in separate Parts so that it will in future be simpler to revise these Parts and also in order that new methods ma
9、y be made available as soon as possible. The revision of the1956 edition was completed in1972 and the first edition was withdrawn, having been superseded by the following fourteen Parts. Part 1: Copper and iron; Part 2: Dissolved oxygen, hydrazine and sulphite; Part 3: Silica and phosphate; Part 4:
10、Aluminium, calcium, magnesium and fluoride; Part 5: Alkalinity, acidity, pH value and carbon dioxide; Part 6: Chloride and sulphate; Part 7: Nitrite, nitrate and ammonia (free, saline and albuminoid); Part 8: Cyclohexylamine, morpholine and long-chain fatty amines; Part 9: Appearance (colour and tur
11、bidity), odour, suspended and dissolved solids and electrical conductivity; Part 10: Sodium, potassium and lithium; Part 11: Anionic, cationic and non-ionic detergents and oil; Part 12: Nickel, zinc, chromates and total chromium and manganese; Part 13: Dichromate value (chemical oxygen demand), non-
12、volatile organic carbon, tannins and chlorine; Part 14: Arsenic, lead and sulphide. 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 itse
13、lf confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to6, 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 indica
14、ted in the amendment table on the inside front cover.BS2690-15:1974 BSI 08-1999 1 1 General 1.1 Reagents. All reagents shall be of recognized analytical reagent quality unless otherwise specified. The concentrations of reagent solutions quoted in this British Standard are, where possible, those show
15、n in Appendix A to BS4245:1968. When solutions differing in concentration from the preferred solutions are required, they are prepared by diluting the preferred solutions in the ratios shown. NOTEThe titles of the British Standards referred to in this standard are listed on the inside back cover. 1.
16、2 Apparatus. The following British Standards relate to apparatus used for carrying out the tests in this standard: BS604, BS846, BS1583, BS1739 and BS1792. 1.3 Water. Subject to the special requirements of certain methods, pure water having a conductivity less than504S/m at20 C when freshly prepared
17、 and measured out of contact with air is to be used whenever water is required. This degree of purity can be achieved by treating water with the correct grades of ion exchange resins. 1.4 Ranges. Where the range of amounts of the substance being determined is stated at the beginning of a test it is
18、usually given in micrograms. The procedures described for the various tests cover the stated ranges, but may in certain cases be extended by taking a smaller volume of the sample and diluting it with water. The test portion shall then be adjusted to the appropriate volume before proceeding with the
19、determination. 1.5 Sampling. It is important to obtain a representative sample; appropriate methods of sampling are described in BS1328. 1.6 Interferences. It should always be realized that, although the methods given will be applicable in almost all cases, occasionally some substance may be present
20、 that will render the method unsuitable. 1.7 Colorimetric methods. It is recommended that the spectrophotometer used for colorimetric determinations should have a band width not exceeding1%of the wavelength at which the measurement is carried out. 2 Definitions For the purposes of this Part of this
21、standard, the following definitions apply: 2.1 EDTA ethylenediamine-NNNN-tetra-acetic acid or its sodium salts, which are used for estimating the hardness of a water and in water treatment 2.2 free EDTA the EDTA, irrespective of its actual form, that is available to complex with calcium or magnesium
22、 in a treated water 2.3 total salts of EDTA the total salts of ethylenediamine-NNNN-tetra-acetic acid including both the free EDTA and the EDTA present in complexes with metals such as calcium or magnesium 3 Free EDTA 3.1 Range. 0.05mg to2.0mg of EDTA, expressed as the tetra-sodium salt. 3.2 Maximum
23、 size of test portion. The maximum size of the test portion is100ml. 3.3 Introduction. The determination is carried out by forming the magnesium complex and detecting the presence of uncomplexed magnesium with mordant black11 1) . EDTA shall be added to compensate for any demand for EDTA in the reag
24、ents. The free EDTA is expressed as the tetra-sodium salt, as this is commonly used in boiler water treatment. 1) Mordant black11 is also available under trade names, e.g.Eriochrome black T or Solochrome black WDFA.BS2690-15:1974 2 BSI 08-1999 3.4 Interferences. Under the conditions described in the
25、 method the presence, separately, in the quantities indicated, of the following in the test solution do not cause significant interference: 3.5 Reagents. The following reagents are required: 1) Ammonium chloride/ammonia, buffer solution. Dissolve71g of ammonium chloride in about300ml of water, add60
26、0ml of ammonia solution, concentrated35%(m/m) (18N), and dilute to one litre. Store in a polyethylene or other suitable plastics bottle. 2) EDTA, 0.002N non-standardized volumetric solution. Dissolve0.372g of disodium dihydrogen ethylenediamine-NNNN-tetra-acetate dihydrate in water and make up to th
27、e mark in a1000ml one-mark volumetric flask. Mix well and store in a polyethylene or other suitable plastics bottle. 3) Magnesium iodate, 0.002N standard reference solution. Dissolve0.446g of magnesium iodate, Mg(IO 3 ) 2 .4H 2 O, in water and make up to the mark in a1000ml one-mark volumetric flask
28、. Mix well. 4) Mordant black indicator solution. Dissolve1g of mordant black11 2)in100ml of triethanolamine. 3.6 Sampling. In order to prevent the oxidation of ferrous iron to ferric iron between sampling and analysis, air shall be excluded. Oxidation of the ferrous iron results in an increase in fr
29、ee EDTA. Reduce the temperature of the sample to less than25 C using a cooling coil and sample lines of stainless steel. Collect the sample in a plastics vessel by upward displacement and make at least one complete volume change; stopper the full vessel. 3.7 Procedure. Measure accurately a suitable
30、volume of the test portion, not greater than100ml and containing not more than2.0mg of EDTA into a250ml beaker. Make up to100ml with water if necessary. Add4.0ml of the ammonium chloride/ammonia buffer solution, followed by about0.4ml of the mordant black indicator solution and, by pipette,5.0ml of
31、the0.002N EDTA solution. Titrate with the magnesium iodate solution from a micro-burette until the first trace of red appears. The titration should be made against a white background and preferably in north daylight or equivalent illumination. Carry out a blank determination using distilled water in
32、stead of the sample. 3.8 Calculation Free EDTA, expressed as the tetra-sodium salt, p.p.m.= 4 Total salts of EDTA 4.1 Range. 254g to3004g of total salts of EDTA, expressed as the tetra-sodium salt. 4.2 Maximum size of test portion. The maximum size of the test portion is35ml. 4.3 Introduction. The m
33、ethod determines the total salts of EDTA in water. The breakdown of the reddish mauve complex of a zirconium salt and xylenol orange by the salts of EDTA results in a range of colours from reddish mauve through red and orange to yellow, and the determination is completed spectrophotometrically at535
34、nm. 4.4 Interferences. Under the conditions described in the method, the presence of6504g of phosphate (PO 4 3 ) in the test solution does not cause significant interference. Aluminium sulphate is added to complex with fluoride ions and so prevents interference. iron (Fe 2+ ) 504g iron (Fe 3+ ) 504g
35、 copper (Cu 2+ ) 504g phosphate (PO 4 3 ) 10mg 2) Mordant black11 is also available under trade names, e.g.Eriochrome black T or Solochrome black WDFA. where a =volume of0.002N magnesium iodate required for the test solution (ml), b =volume of0.002N magnesium iodate required for the blank solution (
36、ml), V =volume of sample taken for the test portion (ml). ab () 380 V -BS2690-15:1974 BSI 08-1999 3 4.5 Reagents. The following reagents are required: 1) Aluminium sulphate solution. Dissolve4.66g of aluminium sulphate (Al 2 (SO 4 ) 3 .16H 2 O) in water and dilute to100ml with water. 2) Xylenol oran
37、ge solution. Dissolve0.135g of xylenol orange in334ml of concentrated hydrochloric acid,36%(m/m) (11N), and add this to a solution of100g of hydroxyl ammonium chloride in300ml to400ml of water. Make up to the mark in a1000ml one-mark volumetric flask and mix well. Allow to stand overnight and filter
38、. 3) Zirconium standard solutions a) Zirconium stock solution. Dissolve1.61g of zirconyl chloride, ZrOCl 2 . 8H 2 O, in65ml of concentrated hydrochloric acid,36%(m/m)(11N), and make up to the mark with water in a1000ml one-mark volumetric flask. Mix well. b) Zirconium working solution. Pipette10.00m
39、l of the zirconium stock solution and5ml of concentrated hydrochloric acid,36%(m/m)(11N), into a250ml one-mark volumetric flask and make up to the mark with water. Mix well. Prepare this solution freshly as required. 4) EDTA standard solutions a) EDTA stock solution. Dissolve0.490g of disodium dihyd
40、rogen ethylenediamine-NNNN-tetra-acetate dihydrate (previously dried at80 C for24h) in water and make up to the mark in a1000ml one-mark volumetric flask. Mix well and store in a polyethylene or other suitable plastics bottle. b) EDTA working solution. Pipette10.00ml of the EDTA stock solution into
41、a500ml one-mark volumetric flask and make up to the mark with water. Mix well. Prepare this solution freshly as required. 1mlN 10.04g of salts of EDTA, expressed as the tetra-sodium salt. 4.6 Preparation of calibration graph. Prepare a fresh calibration graph for each new batch of the zirconium stoc
42、k solution. Into each of a series of seven50ml one-mark volumetric flasks introduce5.00ml of the zirconium working solution and5.00ml of the xylenol orange solution. Into an eighth50ml one-mark volumetric flask introduce5.00ml of the xylenol orange solution. Into the first seven flasks accurately me
43、asure volumes of the EDTA working solution containing04g,504g,1004g,1504g,2004g,2504g and3004g respectively of salts of EDTA, expressed as the tetra-sodium salt. Add5.00ml of the aluminium sulphate solution to each of the eight flasks and make each up to the mark with water. Mix the contents of each
44、 flask well and allow the flasks to stand for at least30min. Measure the optical density of each solution, using20mm cells at a known temperature between20 C and25 C in a spectrophotometer at a wavelength of535nm. Use water in the compensating cell. Deduct the reading for the solution containing xyl
45、enol orange and aluminium sulphate only from those obtained for the standard solutions and plot a calibration graph of optical density against the number of micrograms of salts of EDTA, expressed as the tetra-sodium salt. NOTEThe optical density given by2004g of salts of EDTA expressed as the tetra-
46、sodium salt in the total volume of test solution is approximately0.35. 4.7 Procedure. Pipette into a50ml one-mark volumetric flask5.00ml of the zirconium working solution and5.00ml of the xylenol orange solution. Add to this flask a suitable volume (not greater than35ml) of the sample previously mix
47、ed with5.00ml of the aluminium sulphate solution. Make up to the mark, if necessary, with water and mix well. Pipette into a second50ml one-mark volumetric flask5.00ml of the xylenol orange solution and5.00ml of the aluminium sulphate solution and make up to the mark with water and mix well. Allow t
48、he two flasks to stand for at least30min. Measure the optical densities of the sample solution and the blank solution, using20mm cells in the spectrophotometer at a temperature within1 C of that at which the calibration graph was prepared and at a wavelength of535nm. Use water in the compensating ce
49、ll.BS2690-15:1974 4 BSI 08-1999 4.8 Calculation. Deduct the reading obtained for the solution containing xylenol orange and aluminium sulphate only from that for the sample solution and read off the content of salts of EDTA from the calibration graph. Total salts of EDTA, expressed as the tetra-sodium salt, p.p.m.= 5 Polyacrylate and polymethacrylate 5.1 Range. 504g to100004g of the polymer. 5.2 Maximum size of test portion. The maximum size of test portion shall be100ml. 5.3 Introduction. Physical cond
