1、BRITISH STANDARD BS1647-2: 1984 Incorporating Amendment No. 1 pH measurement Part 2: Specification for reference value standard solutions and operational reference standard solutions UDC 541.132.3:543.25742BS1647-2:1984 This British Standard, having been prepared under the directionof the Laboratory
2、 Apparatus Standards Committee,was published underthe authorityof the Board ofBSI andcomes into effect on 31 December1984 BSI 04-1999 First published, as BS1647, May1950 First revision August 1961 Second Part revision, Part2 The following BSI references relate to the work on this standard: Committee
3、 reference LBC/16 Draft for comment79/55106 DC ISBN 0 580 14100 4 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Laboratory Apparatus Standards Committee (LBC/-) to Technical Committee LBC/16 upon which the following bodies were represe
4、nted: British Kinematograph, Sound and Television Society British Pharmacopoeia Commission Chemical Industries Association Department of Trade and Industry (National Physical Laboratory) Electricity Supply Industry in England and Wales GAMBICA (BEAMA Ltd.) Institute of Medical Laboratory Sciences Ro
5、yal Society of Chemistry Sira Ltd. Society for Applied Bacteriology Society of Chemical Industry Society of Dairy Technology Society of Glass Technology University of Newcastle-upon-Tyne Amendments issued since publication Amd. No. Date of issue Comments 5566 May 1987 Indicated by a sideline in the
6、margin BS1647-2:1984 BSI 04-1999 i Contents Page Committees responsible Inside front cover Foreword ii 0 Introduction 1 1 Scope 1 2 Definitions 1 3 Preparation of the reference value standard solution 1 4 Operational reference standard solutions 1 5 Operational reference standard materials 5 6 Accur
7、acy class 5 Appendix A Test method for the verification of samples of potassium hydrogen phthalate (KHPh) as the reference value standard material 6 Appendix B Preparation of the reference value standard solution 8 Appendix C Method for estimating the phthalic acid content of potassium hydrogen phth
8、alate 8 Appendix D Simple method for establishing the identity of the pH of samples of potassium hydrogen phthalate 9 Appendix E Preparation of operational reference standard solutions 10 Appendix F Determination of pH values of operational reference standard solutions 12 Appendix G Water quality fo
9、r the preparation of reference standard solutions 14 Appendix H Bibliography 15 Figure 1 Cell vessel for certification of samples of potassium hydrogen phthalate as the reference value standard material 7 Figure 2 Cell vessel for determination of pH values of operational reference standard solutions
10、 13 Table 1 pH values of operational reference standard solutions 2 Table 2 Values of the constants for calculating pH values of operational reference standard solutions 3 Table 3 pH values of useful buffer solutions 4 Table 4 Accuracy classes for pH measurements 5 Table 5 Useful data on some operat
11、ional reference standard solutions 11 Table 6 Water for the preparation of standard solutions 15 Publications referred to Inside back coverBS1647-2:1984 ii BSI 04-1999 Foreword This revision, in two Parts, of BS1647 has been prepared under the direction of the Laboratory Apparatus Standards Committe
12、e. This Part together with Part1, supersedes BS1647:1961 which is withdrawn. Part1 of this standard explains the development of the standard and specifies thepH scale. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsibl
13、e 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 and ii, pages1to16, an inside back cover and a back cover This standard has been updat
14、ed (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS1647-2:1984 BSI 04-1999 1 0 Introduction As specified in Part1 of this standard, the reference value standard solution is an aqueous solution of potassium hydrog
15、en phthalate with a molality of0.5mol/kg. Operational pH standards are those assigned pH values at various temperatures based on the operational cell measurements specified in clause4, where the operational reference standard is solutionX and the reference value standard is solution S. Values assign
16、ed by this method for15 operational reference standards are given inTable 1 for various temperatures in the range0 C to60 C. Above60 C values have been obtained by extrapolation of the smoothing equations given in Table 2. NOTE1pH values of operational standards are based on the work reported elsewh
17、ere 1, 2, using liquid junctions formed under highly reproducible conditions. NOTE2Within the pH range3to9, pH values assigned to operational reference standard solutions using the cell without a liquid junction (the method described in Part1 of this standard for assigning the pH to the reference va
18、lue standard solution) are within 0.02 of those given in Table 1 because the residual liquid junction errors are small. Some useful values are tabulated in Table 3. Outside the pH range3 to9, differences may be appreciable and operationally-derived values are preferred. For work of low accuracy clas
19、s, many of the values relating to solutions with specialist application found in the literature could be employed 3. 1 Scope This Part of BS1647 specifies the preparation of the reference value standard solution used as the basis of the pH scale specified in Part1 of this standard and requirements f
20、or operational reference standard solutions suitable for calibration of pH meters against this pH scale. It also specifies accuracy classes for pH measurements. NOTEThe titles of the publications referred to in this Part of this standard are listed on the inside back cover. 2 Definitions For the pur
21、poses of this Part of BS1647 the definitions given in Part1 of this standard apply. 3 Preparation of the reference value standard solution The purity of the material used in the preparation of the reference value standard solution shall be such that the pH value of the solution, when determined by t
22、he method described inAppendix A, is4.005 0.003 at25C. The reference value standard solution shall be prepared as described inAppendix B. NOTEMethods of independently checking the purity of the reference value standard material are described inAppendix C andAppendix D. 4 Operational reference standa
23、rd solution The pH values of the operational reference standard solutions at temperatures between0 C and60 C shall be in accordance with the following equation: where k is the slope factor; pH(S) is the pH value of the reference value standard solution; E(S) and E(X) are the electromotive forces of
24、the operational cells Reference electrode |X|H 2 |Pt Reference electrode | |S|H 2 |Pt The electromotive forces E(X) and E(S) of the operational cells shall be measured consecutively, both cells being at the same temperature throughout, and the same reference electrode shall be used in each cell. NOT
25、E1The hydrogen electrodes in both cells may be replaced by a single glass electrode transferred between the cells, subject to limitations of the glass electrode (seeB.2 in BS1647-1:1984). NOTE2The pH difference, pH(X)pH(S), is calculated. The pH values of the operational reference standard solutions
26、 between60 C and95 C shall be in accordance with the following equation: where the constants A, B, C and D are given in Table 2. NOTE 3Values of pH at various temperatures are given in Table 1. NOTE4The two cells both involve liquid junctions because the reference electrode consists of a calomel or
27、silver/silver chloride electrode in contact with a solution of potassium chloride of fixed concentration. Provided that the filling solution of a single junction reference electrode has a high concentration of potassium chloride (not less than3.5mol/L KCl), or the bridge solution of a double junctio
28、n reference electrode has a high concentration of potassium nitrate (not less than1mol/L), the actual concentration has a negligible effect on the determined value of pH(X). For work of the highest accuracy, it is essential that the junction be formed in a reproducible fashion within a capillary tub
29、e as described in F.2.4. NOTE5If the test solution is chemically incompatible with the reference electrode filling solution, it is necessary to use a bridge solution in the form of a double junction reference electrode. NOTE6Factors pertinent to the choice of reference electrode are described in BS2
30、586. NOTE 7The preparation of the operational standard reference solutions listed in Table 2 is described in Appendix E. (1) (2) pHX ()ABT298.15 ()CT298.15 () 2 + = +DT298.15 () 3BS 1647-2:1984 2 BSI 04-1999 Table 1 pH values of operational reference standard solutions Operational reference standard
31、 solution Temperature (C) 0 10 20 25 30 37 40 50 60 70 80 90 95 0.1mol/kg potassium tetraoxalate 1.475 1.479 1.483 1.490 1.493 1.503 1.513 1.52 1.53 1.53 1.53 0.05mol/kg potassium tetraoxalate 1.638 1.644 1.646 1.648 1.649 1.650 1.653 1.660 1.671 a 1.689 a 1.72 1.73 0.05mol/kg sodium hydrogen diglyc
32、olate 3.470 3.484 3.492 3.502 3.519 3.527 3.558 3.595 Saturated potassium hydrogen tartrate 3.556 3.549 3.544 3.542 3.544 3.553 3.570 a 3.596 a 3.627 a 3.649 a 0.05mol/kg potassium hydrogen phthalate 4.000 3.997 4.000 4.005 4.011 4.022 4.027 4.050 4.080 4.116 4.159 4.208 4.235 0.1mol/L acetic acid+0
33、.1mol/L sodium acetate 4.664 4.652 4.645 4.644 4.643 4.647 4.650 4.663 4.684 4.713 4.75 4.80 4.83 0.01mol/L acetic acid+0.01mol/L sodium acetate 4.729 4.717 4.712 4.713 4.715 4.722 4.726 4.743 4.768 4.800 4.839 a 4.88 4.91 0.02mol/kg piperazine orthophosphate 6.419 6.310 6.259 6.209 6.143 6.116 6.03
34、0 5.952 0.025mol/kg disodium hydrogen orthophosphate+0.025mol/kg potassium dihydrogen orthophosphate 6.961 6.912 6.873 6.857 6.843 6.828 6.823 6.814 6.817 6.830 6.85 6.90 6.92 0.03043mol/kg disodium hydrogen orthophosphate+0.08695mol/kg potassium dihydrogen orthophosphate c 7.506 7.460 7.423 7.406 7
35、.390 7.369 0.04mol/kg disodium hydrogen orthophosphate+0.01mol/kg potassium dihydrogen orthophosphate d 7.488 7.445 7.428 7.414 7.404 0.05mol/kg Tris hydrochloride+0.01667 mol/kg Tris b 8.399 8.083 7.788 7.648 7.513 7.332 7.257 7.018 6.794 0.05mol/kg disodium tetraborate (borax) 9.475 9.347 9.233 9.
36、182 9.134 9.074 9.051 8.983 8.932 8.898 8.88 8.84 8.89 0.01mol/kg disodium tetraborate 9.451 9.329 9.225 9.179 9.138 9.088 9.066 9.009 8.965 8.932 8.91 8.90 8.89 0.025mol/kg sodium hydrogen carbonate+0.025 mol/kg sodium carbonate 10.27 10.154 10.045 9.995 9.948 9.889 9.866 9.800 9.753 9.728 a 9.725
37、a 9.75 9.77 Saturated calcium hydroxide 13.360 12.965 12.602 12.431 12.267 12.049 11.959 11.678 11.423 11.192 a 10.984 a 10.80 10.71 a The last decimal figure is not significant but is included to facilitate smooth interpolation. b NOTETris=Tris(hydroxymethyl) aminomethane. c = ratio of 3.5 : 1. d =
38、 ratio of 4 : 1.BS1647-2:1984 BSI 04-1999 3 Table 2 Values of the constants for calculating pH values of operational reference standardsolutions pH(X)=A + B(T 298.15)+C(T 298.15) 2 + D(T 298.15) 3 Operational reference standard solution Constant A 10 4 B 10 6 C 10 7 D 0.1mol/kg potassium tetraoxalat
39、e 1.4787 8.708 7.756 1.266 0.05mol/kg potassium tetraoxalate 1.6462 3.184 8.733 3.136 0.05mol/kg sodium hydrogen diglycolate 3.4924 18.871 27.983 0.4838 Saturated potassium hydrogen tartrate 3.5555 14.752 40.281 0.0301 0.05mol/kg potassium hydrogen phthalate 4.0048 10.007 32.745 0 0.1mol/L acetic ac
40、id+0.1mol/L sodium acetate 4.6435 0.7529 31.991 0.9828 0.01mol/L acetic acid+0.01mol/L sodium acetate 4.7130 2.910 37.174 0.1575 0.02mol/kg piperazine orthophosphate 6.2589 100.99 39.601 0.4978 0.025mol/kg disodium hydrogen orthophosphate+0.025mol/kg potassium dihydrogen orthophosphate 6.8567 29.777
41、 49.338 0.8568 0.03043mol/kg disodium hydrogen orthophosphate+0.08695mol/kg potassium dihydrogen orthophosphate 7.4060 32.435 17.178 5.439 0.04mol/kg disodium hydrogen orthophosphate+0.01mol/kg potassium dihydrogen orthophosphate 7.4277 31.767 80.661 14.713 0.05mol/kg Tris hydrochloride+0.01667mol/k
42、g Tris a 7.6484 274.70 96.190 2.493 0.05mol/kg disodium tetraborate (borax) 9.1818 98.9233 75.587 0.9281 0.01mol/kg disodium tetraborate 9.1793 87.021 81.179 2.189 0.025mol/kg sodium hydrogen carbonate+0.025mol/kg sodium carbonate 9.9947 96.703 67.187 3.571 Saturated calcium hydroxide 12.4305 334.88
43、 141.78 2.037 a Tris=Tris(hydroxymethyl) aminomethane.BS 1647-2:1984 4 BSI 04-1999 Table 3 pH values of useful buffer solutions Buffer solutions Temperature (C) 0 5 10 15 20 25 30 35 37 40 45 50 0.01mol/L HCl+0.09mol/L KCl 2.07 3.08 0.05mol/L potassium dihydrogen citrate 3.86 3.84 3.82 3.80 3.79 3.7
44、8 3.78 3.76 3.76 3.75 3.75 3.75 0.01mol/L phenylacetic acid+0.01mol/L sodium phenylacetate 4.27 4.27 4.28 4.29 4.30 4.32 4.33 4.38 0.02mol/L Bis-Tris+0.02mol/L Bis-Tris HCl (1) 7.00 6.91 6.81 6.72 6.64 6.55 6.47 6.39 6.36 6.31 6.24 6.17 0.06mol/L tricine+0.02mol/L sodium tricinate (2) 8.02 7.92 7.81
45、 7.71 7.62 7.53 7.43 7.41 7.36 7.28 7.20 0.05mol/L tricine+0.05mol/L sodium tricinate (2) 8.49 8.38 8.27 8.18 8.08 7.99 7.90 7.86 7.82 7.74 7.66 NOTE1Bis (hydroxymethyl) aminotris (hydroxyethyl) methane; dry at80 C. NOTE2Tris (hydroxymethyl) methylglycine.BS1647-2:1984 BSI 04-1999 5 NOTE 8The refere
46、nce value standard solution specified in clause3 is also suitable for use as an operational reference standard solution and is therefore included in Table 1. No distinction need be made between the reference value standard solutions and operational reference standard solutions when choosing the best
47、 one to employ for a particular pH measurement. 5 Operational reference standard materials The pH value of a solution of an operational reference standard material prepared by the appropriate method described inAppendix E and tested as described in Appendix F shall differ by no more than0.003 from t
48、he values given in Table 1 at the test temperature which shall be either20 C or25 C. If certified operational reference standard material is not available, or not available in sufficient quantity, the procedures described inAppendix D andAppendix F shall be employed to ensure that the selected recog
49、nized analytical grade material satisfies the above requirement if the accuracy class of the desired measurements warrants this. Operational reference standard materials supplied in prepackaged form for the preparation of a stated volume of operational reference standard solution shall state on the package the tolerance on the pH value the user may expect when the solution is prepared at20 C in grade B
