BS 2586-1979 Specification for glass and reference electrodes for the measurement of pH《pH值测量用玻璃电极与参比电极规范》.pdf

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1、BRITISH STANDARD CONFIRMED JANUARY1993 BS2586:1979 Incorporating Amendment Nos.1 and2 Specification for Glass and reference electrodes for the measurement of pH UDC 543.257.2BS2586:1979 This British Standard, having been prepared under the directionof the Laboratory Apparatus Standards Committee,was

2、 published underthe authority of the Executive Board and comesintoeffect on 31 October1979 BSI 12-1999 First published March1955 First revision May1965 Second revision October1979 The following BSI references relate to the work on this standard: Committee reference LBC/16 Draft for comment 77/51060

3、DC ISBN 0 580 10873 2 Cooperating organizations The Laboratory Apparatus Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Agricultural Research Council Ass

4、ociation for Science Education British Laboratory Ware Association British Lampblown Scientific Glassware Manufacturers Association Limited British Pharmacopoeia Commission* Chemical Industries Association* Chemical Society* Chemical Society, Analytical Division* Department of Health and Social Secu

5、rity Department of Industry(Laboratory of the Government Chemist) Department of Industry(National Physical Laboratory)* Glass Manufacturers Federation Institute of Petroleum Ministry of Defence Pharmaceutical Society of Great Britain Scientific Instrument Manufacturers Association* Society of Chemic

6、al Industry* Society of Glass Technology* Standardization of Tar Products Tests Committee The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: British Kinematograp

7、h, Sound and Television Society Imperial Chemical Industries Limited Institute of Medical Laboratory Sciences Royal Institute of Chemistry Royal Society Sira Institute Society for Applied Bacteriology Society of Dairy Technology University of Newcastle Upon Tyne Individual expert Amendments issued s

8、ince publication Amd. No. Date of issue Comments 3569 April1981 5668 October1987 Indicated by a sideline in the marginBS2586:1979 BSI 12-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii Section 1. General 1 Scope 1 2 References 1 3 Definitions 1 Section 2. pH glass elect

9、rodes 4 pH range and usable temperature range 2 5 General construction and electrical requirements 2 6 Performance requirements at25 C 3 7 Information to be given integrally with the pH glass electrode 3 8 Summary of information to be given in the literature provided with pH glass electrodes 3 Secti

10、on 3. Reference electrodes 9 Requirements 4 10 Summary of information to be given in literature provided with reference electrodes 5 Section 4. pH combination or dual electrodes 11 Requirements 5 12 Summary of information to be given in literature provided with combination electrodes 5 Appendix A Me

11、thod of testing performance of pH glass electrodes 7 Appendix B Performance tests for reference electrodes 11 Table 1 Maximum permitted glass electrode errors at25 C dependent on stated usable upper pH limit 4 Table 2 Composition of special buffer solutions 7 Table 3 Observed potential differences (

12、in millivolts) for a perfect electrode responding to hydrogen ions transferred between Na + -free solutions 8 Table 4 Observed potential differences (in millivolts) for a perfect glass electrode transferred between solutions of various Na +concentrations at approximately constant pH 8 Publications r

13、eferred to Inside back coverBS2586:1979 ii BSI 12-1999 Foreword This British Standard, which has been prepared under the direction of the Laboratory Apparatus Standards Committee, was first published in1955 in an attempt to reduce differences which had been encountered in certain characteristics of

14、glass electrodes, such as dimensions, efficiency of performance and electrical resistance. The1965 revision and the present revision are the result of further consideration in the light of continuing developments and technological advances. There is a variety of shapes and configurations for the pH-

15、sensitive region of glass electrodes, appropriate to the wide range of applications in which they are used. Accordingly, unlike the previous editions, the present revision does not require adherence to specified dimensions. Manufacturers are, however, recommended to provide certain information regar

16、ding dimensions as suggested in8.2. The division of electrodes into categories such as “general purpose”, “wide range”, etc.has been abandoned but, based on development of a new method of testing the performance of glass electrodes, the manufacturer should now only claim as the usable pH range of a

17、glass electrode those limits of pH between which its performance is in accordance with the requirements of this British Standard. Furthermore, the sodium ion error of the glass electrode at selected pH values greater than7 and the acid error at pH values less than1 can now be readily measured by the

18、 manufacturer and checked by the user using procedures described in Appendix A. An additional important feature of this revision is the inclusion of reference electrodes. The correct functioning of the reference electrode in pH measurements is of equal importance to that of the glass electrode, alth

19、ough this has not always been appreciated. Tests are now incorporated, in Appendix B, which enable the characteristics of reference electrodes to be assessed; these tests will aid in the selection of electrodes of proper design for particular applications. In accordance with current practice, variou

20、s types of connector to the pH meter are permitted. Standardization in this area is desirable and it is the hope of the technical committee responsible for this British Standard that the bayonet normal connector(BNC) type will be adopted internationally in the near future. A British Standard does no

21、t 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 f

22、ront cover, pagesi andii, pages1 to12, 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.BS2586:1979 BSI 12-1999 1 Section 1. General 1 Scope Thi

23、s British Standard specifies the performance requirements and other essential characteristics of glass electrodes responsive to hydrogen ions, reference electrodes and glass combination electrodes for general laboratory use. 2 References The titles of the publications referred to in this standard ar

24、e listed on the inside back cover. 3 Definitions For the purposes of this British Standard the following definitions apply. 3.1 pH glass electrode electrode responsive to hydrogen ions and consisting of a bulb, or other suitable form made of a special glass, attached to a stem of high resistance mat

25、erial, complete with internal reference electrode(see3.9) and internal filling solution(see3.10) 3.2 pH-sensitive region bulb, or other suitable form, of special glass composition which makes the electrode hydrogen ion responsive 3.3 pH meter high impedance instrument by means of which either the pH

26、 value of a solution, or the potential difference between electrodes immersed in a solution, is indicated 3.4 screened cable coaxial shielded cable connecting the internal reference electrode system to a plug for input to the measuring device(pH meter) NOTESome glass electrodes may be provided with

27、detachable screened cables. 3.5 screened(pH glass) electrode pH glass electrode in which the screening is continued almost down the whole length of the stem of the electrode 3.6 pH combination or dual electrode electrode in which a pH glass electrode and an external reference electrode system togeth

28、er with the liquid junction are combined in a single probe. In the usual construction of pH combination electrodes, the reference electrode is concentric with, and outside the stem of, the glass electrode, which does not then require additional electrical screening 3.7 zero point value of the pH of

29、a solution which, in combination with a stated external reference electrode, gives zero e.m.f. from the cell 3.8 slope factor temperature dependent factor relating potential and pH, tabulated in BS1647 3.9 internal reference electrode (of pH glass electrode) electrode, for example silver/silver chlo

30、ride, terminating the screened input cable to the pH meter, and in contact with the internal filling solution 3.10 internal filling solution(of pH glass electrode) aqueous electrolyte solution, which may be gelled, containing a fixed concentration of hydrogen ions, i.e.a buffer solution, and a fixed

31、 concentration of the ion to which the inner reference electrode is reversible, e.g.chloride ion in the case of silver/silver chloride or calomel electrodes 3.11 liquid junction any junction between two electrolyte solutions of different composition. Across such a junction there arises a potential d

32、ifference, called the liquid junction potential. In the operational pH cell(see3.12) the junction is between the test solution, or the pH standard solution, and the filling solution of the reference electrode 3.12 operational pH cell electrochemical cell which is the basis of practical pH measuremen

33、ts, consisting of a glass electrode and a reference electrode(see3.13) dipping in the test solutionBS2586:1979 2 BSI 12-1999 3.13 reference electrode external electrode system which incorporates a means of forming the liquid junction (see3.11) such as a ceramic plug or frit. Usually, this reference

34、electrode system has either a calomel or a silver/silver chloride inner element in contact with a concentrated solution of potassium chloride(KCl) as filling solution(see3.17) 3.14 isopotential method method of correcting for small differences in temperature between test and standard solutions, or b

35、etween a glass and a remote external reference electrode at different temperature, based on the approximately linear temperature dependence of those contributions to the measured e.m.f. of the cell which are independent of the composition of the test and standard solutions 3.15 isopotential pH point

36、 the pH value at which the e.m.f. of a particular pH glass electrode/reference electrode pair, comprising the operational cell(see3.12), may be independent of temperature. It is determined as the point of intersection on a graph of e.m.f. of the operational cell versus pH value for two temperatures

37、differing by at least20 C 3.16 pH glass electrode error deviation of a pH glass electrode from the hydrogen ion response function. An example often encountered is the error due to sodium ions at alkaline pH values, which results in a low pH value being indicated 3.17 filling solution(of a reference

38、electrode) solution containing the anion to which the reference electrode of the operational pH cell is reversible, e.g.chloride for a silver/silver chloride electrode. In the absence of a bridge solution(see3.18), a filling solution of a high concentration comprising cations and anions of almost eq

39、ual mobility is employed as a means of maintaining the liquid junction potential small and approximately constant on substitution of test solution for standard solution(s) 3.18 bridge solution(of a double junction reference electrode) solution of high concentration of inert salt, preferably comprisi

40、ng cations and anions of almost equal mobility, optionally interposed between the reference electrode filling solution(see3.17) and both the test and pH standard solution, when the test solution and filling solution are chemically incompatible. This procedure introduces a second liquid junction into

41、 the operational cell and is usually formed in a similar way to the first Section 2. pH glass electrodes 4 pH range and usable temperature range 4.1 pH range. The manufacturer shall state(seeclauses7 and8) the pH range for which a glass electrode is usable. The performance of this glass electrode in

42、 the specified range shall be in accordance with the limits laid down in clause6 and determined using the method described in Appendix A. 4.2 Temperature range. The manufacturer shall state(seeclauses7 and8) the usable temperature range of the pH glass electrode and, if appropriate, a permissible me

43、thod of heat sterilization. NOTECurrently, laboratory pH glass electrodes are available for pH ranges0 to11, 0 to12 or0 to14 and temperature range0 C to100 C. For special purposes, low temperature(below0 C) and high temperature(above100 C) electrodes may be available from some manufacturers. 5 Gener

44、al construction and electrical requirements 5.1 Electrical resistance 5.1.1 The d.c.resistance of the electrode(membrane resistance) measured at25 C shall not exceed1G7. 5.1.2 For special electrodes, e.g.high temperature electrodes or microelectrodes, a higher d.c. resistance is permitted provided t

45、hat this is stated(see8.1). Values at temperatures other than25 C may be stated, if appropriate. NOTEThe membrane resistance and insulation resistance may be determined with a meter for measuring high d.c.resistance which applies a voltage less than500V. Highly reproducible values are not usually ob

46、tainable because of the effect of the polarizing voltage on the glass electrode and the electrode may not be usable for some hours after the test. Alternatively and preferably, the following method may be employed, using the pH meter itself as the measuring instrument and a known high value, screene

47、d resistor(R s . 100M7). Immerse the pH glass electrode and reference electrode in any standard pH buffer solution at25 C. Record the reading (V 1 ) and then shunt the input with the resistor and record the new value (V 2 ). The glass electrode resistance is then given by R s (V 1 V 2 )/V 2 .BS2586:

48、1979 BSI 12-1999 3 5.2 Screening, insulation and connector. Thescreened cable to the internal reference electrode shall be of the low noise, flexible type and terminate in a suitable screened plug appropriate to the pH meter being used. It is recommended that the manufacturer should statesee8.2 b) w

49、hat screened plug has been fitted to the pH glass electrode. The insulation resistance, measured using a suitable meter for high d.c.resistance, between the internal conductor to the internal reference electrode and the screen on the plug, shall be at least1000times greater than the membrane resistance measured at the same temperature. NOTE 1 A number of suitable screened plug connectors are commonly in use. These include the(television aerial) coaxial connector specified as type1 in BS3041-2 as well as foreign types. However, BNC connectors are strongly pr