1、Designation: D2284 11Standard Test Method forAcidity of Sulfur Hexafluoride1This standard is issued under the fixed designation D2284; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenthes
2、es indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the acidicfluorides of sulfur hexafluoride (SF6).1.2 The values stated in SI units are to be regarded asstand
3、ard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the appli
4、ca-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water3. Summary of Test Method3.1 Acidic constituents of the sample are absorbed inslightly alkaline water containing an indicator and the excessbase titrated with a standard a
5、cid solution. The resultant acidityis expressed as equivalents of hydrofluoric acid (HF).4. Significance and Use4.1 Acidic fluorides are undesirable in SF6used as anelectrical insulating gas in that they may contribute to corro-sion or constitute dielectric hazard.4.2 This test method is valid for b
6、oth new and used SF6.Inused SF6, it will only measure those active species which arehydrolyzable.5. Apparatus5.1 Gas Washing Bottles, 500-mL capacity, two required.5.2 Microburet, graduated to 0.01 mL.5.3 Wet Test Meter.NOTE 1The meter is used to measure the volume of dry gas in litersand hence the
7、weight of SF6samples. The density of sulfur hexafluorideat 0C and 1 atm. of pressure (STP) is 6.52 g/L. The density of sulfurhexafluoride at 25C and 1 atm. of pressure (normal temperature andpressure) is 5.97 g/L. Alternatively, the sample weight may be determinedby weighing the sample cylinder befo
8、re and after sampling.6. Reagents6.1 Purity of ReagentsUse reagent grade chemicals in alltests. Unless otherwise indicated, it is intended that all reagentsshall conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society, wheresuch specifications are availa
9、ble.3Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent grade waterconformi
10、ng to Specification D1193.6.3 Phenolphthalein Indicator Solution (10 g/L)Dissolve1 g of phenolphthalein in 100 mL of ethanol (95 %).6.4 Sodium Hydroxide Solution (0.01 N)Dissolve 0.4 60.01 g of sodium hydroxide (NaOH) in water and dilute to 1 L.Prepare a fresh solution weekly. Standardize by titrati
11、ngagainst a weighed amount of potassium acid phthalate.6.5 Sulfuric Acid (0.01 N)Add 0.25 mL of concentratedsulfuric acid (H2SO4, sp gr 1.84) to water and dilute to 1 L.Standardize against standard 0.01 N NaOH solution.7. Sampling7.1 Take the sample as a liquid from the cylinder to besampled. This m
12、ay be done by inverting the cylinder so that theoutlet valve is at the bottom.8. Preparation of Apparatus8.1 Place the cylinder to be sampled as suggested in Section7 and connect a needle valve to the cylinder outlet. Connect the1This test method is under the jurisdiction of ASTM Committee D27 onEle
13、ctrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D27.06 on Chemical Test.Current edition approved May 1, 2011. Published May 2011. Originallyapproved in 1964 as D2284 64T. Last previous edition approved in 2002 asD2284 95(2002) which was withdrawn January 2011 a
14、nd reinstated in May 2011.DOI: 10.1520/D2284-11.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted b
15、y the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
16、shohocken, PA 19428-2959, United States.inlet of one of the gas sampling bottles to the cylinder needlevalve and the outlet to the wet test meter. Flexible rubber orplastic tubing can be used. Set the meter to zero and note thereading.9. Procedure9.1 Boil 600 mL of deionized water in a 1-L beaker fo
17、rabout 5 min and cool quickly to room temperature. Add 10drops of phenolphthalein indicator solution and enough 0.01 NNaOH solution to color the solution faintly pink. Pour half ofthe solution into each of the two gas washing bottles and add2.00 mL of 0.01 N NaOH solution to each. Replace the caps o
18、nboth bottles and set one aside to serve as a blank.NOTE 2Every precaution should be taken to ensure that both solutionsare treated in an identical manner to ensure that the quantities ofatmospheric contaminants such as CO2or other acidic vapors absorbedinto the test and blank solutions are equal.9.
19、2 After placing the gas sampling tube in position (seeSections 7 and 8) carefully open the sample cylinder needlevalve so that the sample gas passes through the solution at arate of about 1 L/min. After 6 to 8 L of sample have passedthrough the tube, close the needle valve, remove the bubbler,and re
20、cord the gas meter reading. Note that the sensitivity ofthe technique may be increased by using a larger volume ofgas.NOTE 3Terminate sampling immediately if the solution fades to apale pink.9.3 Titrate the solution in each of the gas washing bottleswith standard 0.01 N H2SO4until they are faintly p
21、ink andmatch in color exactly.10. Calculation10.1 Calculate the acidity as HF as follows:Acidity as HF, mL/kg ppm!5B 2 A!N 3 0.020DW3 106where:A =H2SO4required by the sample solution, mLB =H2SO4required by the blank solution, mLD = density of SF6gas, g/L,N = normality of the H2SO4, andW = sample use
22、d, L.NOTE 4When using the sample weight rather than the volume, bubblea minimum of 50 g of sample and use the weight of the sample as thedenominator of the above equation.11. Precision and Bias11.1 PrecisionThe repeatability standard deviation on thedifference between two test results at an average
23、value of 1.12mL of titrant has been determined to be 60.018 for a singleoperator in a single laboratory. The 95 % repeatability limit forduplicate determinations should agree within 7.1 % of theaverage of the two results. It is not feasible to specify thereproducibility of the procedure at this time
24、 because no otherlaboratories have been found to participate in an ILS study. Thedata used to determine the precision is provided in Table 1.11.2 BiasSince there is no accepted reference materialsuitable for determining the bias of acidity in sulfur hexafluo-ride, no statement on bias can be made.11
25、.3 Detection LimitThe calculated lower limit is 0.04ppm acidity as HF based on the burette which has a 0.01 mLincrement.12. Keywords12.1 acid; electrical; fluoride; gas; hexafluoride; insulating;sulfurASTM International takes no position respecting the validity of any patent rights asserted in conne
26、ction with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsi
27、ble technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful co
28、nsideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100
29、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM we
30、bsite(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).TABLE 1 Data Used to Develop the Repeatability StatementSample A mL of titrantTest 1 1.14Test 2 1.10Test 3 1.14Test 4 1.12Test 5 1.10Average 1.12Standard Deviation 0.0179Number of Determinations 5Number of DE (n 1) 4Minimum Value 1.10Maximum Value 1.1495 % Repeatability, ASTM 60.08ASTM Repeatability of Average 7.1 %D2284 112
