1、Designation: E538 17aStandard Test Methods forMercury in Caustic Soda (Sodium Hydroxide) and CausticPotash (Potassium Hydroxide)1This standard is issued under the fixed designation E538; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover the routine determination ofmercury in caustic soda and caustic potash liquo
3、rs and anhy-drous caustic soda in the solid, flake, ground, and bead form bythe flameless atomic absorption method.1.2 Two test methods are described as follows: Test MethodA employs a direct analysis of the sample using an alkalinereducing agent with a lower limit of detection of 0.1 ppb(ng/g). Tes
4、t Method A was developed using caustic soda andcaustic potash. Test Method B requires a preliminary neutral-ization of the sample followed by a permanganate oxidationbefore it can be analyzed by an acidic reducing agent with alower limit of detection of this test method of 0.01 ppm (g/g).Test Method
5、 B was developed using caustic soda.1.3 Review the current Safety Data Sheets (SDS) for de-tailed information concerning toxicity, first-aid procedures, andsafety precautions.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1
6、.5 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 applica-bility of regulatory limitations prior to use. Specific hazard
7、sstatements are given in Sections 7 and 18.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the Wo
8、rld Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE180 Practice for Determining the Precisio
9、n of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals (Withdrawn 2009)3TEST METHOD AALKALINE REDUCING AGENT3. Summary of Test Method3.1 All forms of mercury are reduced to metallic mercurywhich is aerated from the solution and determined by coldvapor atomic absorption anal
10、ysis.4. Significance and Use4.1 Mercury is a toxic material and is also deleterious ifpresent in caustic soda and caustic potash used in certainmanufacturing processes. It must therefore be controlled as apossible pollutant. These test methods provide a procedure formeasuring mercury in liquid and s
11、olid caustic soda and causticpotash.5. Apparatus5.1 Atomic Absorption Spectrophotometer, equipped withmounting to hold an absorption cell and a fast response (0.5-s)recorder.5.2 Mercury Hollow Cathode Lamp, primary line 253.7 nm.5.3 Absorption Cell, 10-cm path length with quartz win-dows.5.4 Gas Was
12、hing Bottle, 125-mL, with extra-coarse frittedbubbler. The bottle has a calibration line drawn at the 60-mLmark.1These test methods are under the jurisdiction of ASTM Committee D16 onAromatic, Industrial, Specialty and Related Chemicals and are the direct responsi-bility of Subcommittee D16.15 on In
13、dustrial and Specialty General Standards.Current edition approved July 1, 2017. Published July 2017. Originally approvedin 1975. Last previous edition approved in 2017 as E538 17. DOI: 10.1520/E0538-17a.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Ser
14、vice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.*A Summary of Changes section appears at the end of this standardCopyright
15、 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International
16、Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15.5 Gas Washing Bottle, 125-mL, without frit.5.6 Stopcock, three-way, with TFE-fluorocarbon plug.5.7 Needle Valve.5.8 Drying Tube.5.9 Vacuum Trap.5.10 Flowmeter, capable of measu
17、ring and maintaining aflow rate of 1.5 standard ft3/h.NOTE 1The procedure as described in this test method employs aPerkin-Elmer Model 303 atomic absorption spectrophotometer.Any otherequivalent atomic absorption spectrophotometer may be used as well asthe many commercial instruments specifically de
18、signed for measurementof mercury by flameless atomic absorption now available. However,variation in instrument geometry, cell length, sensitivity, and mode ofresponse measurement may require appropriate modifications of theoperating parameters.6. Reagents6.1 Purity of ReagentsUnless otherwise indica
19、ted, it isintended that all reagents shall conform to the specifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society, where such specifications are available.4Othergrades may be used, provided it is first ascertained that thereagent is of sufficiently high purity to permit
20、 its use withoutlessening the accuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean Type II or III reagentwater conforming to Specification D1193.6.3 Anhydrous Magnesium Perchlorate.6.4 Sodium Hydroxide 50 %Membrane grade caustic
21、soda50 %.6.5 Aqua RegiaCarefully add 10-mL of concentratedHNO3(sp gr 1.42) to 30 mL of concentrated HCl (sp gr 1.19)in a 100-mLbeaker. Let the mixture stand for 5 min before use.This mixture is unstable and should not be stored. (WarningUse goggles when preparing this solution.)6.6 Cadmium Chloride
22、Solution (10 g/100 mL)Dissolve10 g of cadmium chloride in 50 mL of water and then add 50mL of 50 % membrane grade caustic soda. Cadmium hydrox-ide will precipitate upon the addition of the caustic soda. Thissolution must be well shaken before use. (WarningUsegoggles when preparing this solution.)6.7
23、 Stannous Chloride Solution (10 g/100 mL)Dissolve10 g of stannous chloride (SnCl22H2O) in 100 mL of water.Prepare fresh once a week.6.8 Mercuric Nitrate Stock Solution (0.05 M) (1 mL= 10 mgHg)Dissolve 17.1 g of mercuric nitrate (Hg(NO3)2H2O) in100 mL of water containing 2 mL of concentrated HNO3in a
24、1-L volumetric flask. Dilute to volume with water and mixwell.6.9 Mercury Standard Solution (1 mL = 50 g Hg)Pipet5.0 mL of 0.05 M mercuric nitrate stock solution into a 1-Lvolumetric flask, acidify with 5 mL of H2SO4(1+4), and diluteto volume with water. Mix well.6.10 Mercury Standard Solution (1 mL
25、 = 50 ng Hg)Pipet1.0 mL of the standard mercury solution containing 50 gHg/mLinto a 1-Lvolumetric flask, acidify with 5 mLof H2SO4(1+4), and dilute to volume with water. Mix well.6.11 Mercury Standard Solution (1mL=5ngHg)Pipet10.0 mL of the standard mercury solution containing 50 ngHg/mL into a 100m
26、L volumetric flask, acidify with 5 mL ofH2SO4(1+4), and dilute to volume with water. Mix well,Prepare fresh daily.6.12 Sulfuric Acid (1+4)Add slowly while stirring 200mL of concentrated H2SO4(sp gr 1.84) to 800 mL of water.This solution is dispensed from a 10-mL buret. (WarningUse goggles when prepa
27、ring this solution.)7. Hazards7.1 Sodium hydroxide, potassium hydroxide, and their so-lutions are extremely corrosive. Any splashes on the skin oreyes must be flushed with cold water. It is important that theeyelids be held open during the flushing period. Get medicalattention immediately for any ey
28、e exposures.8. Calibration8.1 Take care to avoid contamination of the apparatus withmercury. Soak all glass apparatus (pipets, beakers, and gas-washing bottle) in aqua regia before use. Rinse thoroughly withwater.8.2 Connect the apparatus shown in Fig. 1 to the atomicabsorption spectrophotometer and
29、 adjust the air flow rate to 1.5standard ft3/h (see Notes 2 and 3).NOTE 2The magnesium perchlorate in the drying tube should bereplaced frequently. A cork stopper should be used with the drying tube.All connections between glass should be made with minimum lengths ofvinyl tubing.NOTE 3The optimum fl
30、ow rate will vary with the geometric design ofeach apparatus. The flow rate should be adjusted to give the maximumabsorbance and the best reproducibility without excessive foaming.8.3 Adjust the operating conditions in accordance with thefollowing parameters and allow the spectrophotometer to warmup
31、 for at least 15 min. Select the proper scale expansion for the4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals,
32、BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD. FIG. 1 Mercury Aeration ApparatusE538 17a2standards used from Table 1. The conditions shown are for thePerkin-Elmer Model 303 (Note 1).Wavelength 253.7 n
33、mSlit width 4 (6.5 )Lamp current approximately 10 mARecorder noise suppression 2, giving approximately 90 % ofresponse in 1 sScale expansion 38.4 Allow the base line to stabilize with Stopcock A in thebypass position and an empty gas-washing bottle connected tothe apparatus.8.5 Prepare a reagent bla
34、nk by adding 20 mL of 50 %membrane grade caustic soda into the gas-washing bottle.8.6 Add 2 mL of the cadmium chloride solution into thegas-washing bottle.8.7 Add 20 mLof water to the gas-washing bottle by slowlydelivering the water down the side of the bottle. This will layerthe water on top of the
35、 cadmium chloride solution andminimize premature mixing of the reagents.8.8 Add 2 mL of SnCl2solution to the gas-washing bottledelivering the solution down the side of the bottle and connectthe gas-washing bottle to the aeration apparatus.Turn StopcockA from the bypass to the aeration position and a
36、erate thesolution.8.9 Determine the percent absorption from the peak heighton the recorder chart when a constant reading is obtained.NOTE 4Steps 8.5 8.9 should be carried out in sequence with as littledelay as possible between operations.8.10 An absorption peak of less than 10 % should beobtained at
37、 3 scale expansion. Continue running blanks untilthis is achieved. Consistently higher blanks indicate a contami-nation problem from dirty glassware or reagents. Clean theapparatus with aqua regia and prepare fresh reagents until asatisfactory blank is obtained.8.11 The concentration of mercury in t
38、he standards shouldcover the expected concentration in the sample to be analyzed.Table 1 suggests the standards to be prepared for variousconcentration levels. Prepare a series of at least three standardsin 150-mL borosilicate extraction flasks in accordance withTable 2. Analyze each standard by add
39、ing it with the water in8.7 and completing the analysis as described in 8.8 to 8.9.8.12 Repeat Steps 8.5 8.11 for each reagent blank andstandard in order of increasing concentration.8.13 Convert the values for percent absorption to absor-bance using the tables in the instrument instruction manual or
40、an optical density scale ruler. Subtract the absorbance of thereagent blank from the absorbance of each standard. Draw acalibration curve by plotting absorbance versus nanograms ofmercury. At 3 scale expansion, the readings in recorder chartdivisions are approximately equal to absorbance and may beu
41、sed directly as the ordinate of the calibration curve.8.14 Alternatively, in instruments where the signal is re-corded in percent absorption, semilog paper can be used to plotpercent absorption versus concentration.Agood deal of time issaved using this method of plotting a calibration curve.59. Anal
42、ysis of Sample9.1 Select a sample size in accordance with the anticipatedmercury concentration from Table 1.9.2 The sample, in the form of 50 % caustic soda or causticpotash, is added to the gas-washing bottle before the 50 %membrane caustic soda in 8.5. Weigh the amount of sampleadded to the gas-wa
43、shing bottle to the nearest 0.01 g. Whenlarge samples of caustic soda are analyzed, the volume of 50 %membrane caustic soda added to the gas-washing bottle shouldbe reduced to keep the total concentration of caustic soda in thefinal solution in the gas-washing bottle at or below 25 %.9.3 Proceed wit
44、h 8.5 8.11 for each sample to be analyzed.9.4 Convert the values for percent absorption to absorbanceas described in 8.13 and 8.14. Subtract the absorbance of thereagent blank carried through the entire procedure from theabsorbance of the sample. Obtain the nanograms of mercury inthe sample from the
45、 calibration curve.5Harre, Gustav N., Atomic Absorption News Letter, Vol 8, No.2, 1969.TABLE 1 Expected Range and Sample SizeTest Method AExpected Range,ng/gSample Size, g Standards, ng Scale Expansion60 1 10, 50, 100 330-60 2.5 10, 50, 100 315-30 5 10, 50, 100 37-30 10 10, 50, 100 33-7 20 10, 50, 1
46、00 33 40 0.5, 10, 50 3Test Method BExpected Range,g/gSample Size, g Standards, g Scale Expansion0.2 to 10 2 2,5,10,20 10.01 to 0.5 5 0.2,0.5,1,2 3TABLE 2 Standard Stock SolutionsTest Method Ang Hg inStandardmL of water in gasbottlemL of 50 ng/mLHg StandardmL of 5 ng/mLHg Standard0.0 20 . . . 0.00.5
47、20 . . . 0.12.5 20 . . . 0.55.0 19 . . . 1.010 20 0.2 . . .50 19 1.0 . . .100 18 2.0 . . .500 10 10 . . .1000 0 20 . . .Test Method Bg Hg in Standard mL of NaCl BrinemL of 10 g/mL HgStandard SolutionmL of 1 g/mL HgStandard Solution0.1 5 . . . 0.10.2 5 . . . 0.20.3 5 . . . 0.30.5 5 . . . 0.51.0 5 . .
48、 . 1.02.0 5 . . . 2.05 5 . 5.010 5 1.0 .20 5 2.0 .E538 17a310. Calculation10.1 Calculate the mercury content of the sample as fol-lows:Hg, ppb 5AB(1)where:A = mercury in sample, ng, andB = sample weight, g.11. Report11.1 Report the parts per billion mercury to the nearest 0.01ppb.12. Precision and B
49、ias12.1 The following criteria should be used in judging theacceptability of results (Note 5):12.1.1 Repeatability (Single Analyst)The standard devia-tion and coefficient of variation for a single determination hasbeen estimated to be the values listed in Table 3 at the indicateddegrees of freedom. The 95 % limits for the difference betweentwo such runs are also listed in Table 3.12.1.2 Laboratory Precision (Within-Laboratory, BetweenDays Variability)The laboratory precision for this testmethod has not been d
