1、Designation: E 538 98 (Reapproved 2003)e1Standard Test Methods forMercury in Caustic Soda (Sodium Hydroxide) and CausticPotash (Potassium Hydroxide)1This standard is issued under the fixed designation E 538; the number immediately following the designation indicates the year oforiginal adoption or,
2、in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEWarning notes were editorially moved into the standard in May 2003.1. Scope1.1 These t
3、est methods cover the routine determination ofmercury in caustic soda and caustic potash liquors 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 th
4、e sample using an alkalinereducing agent with a lower limit of detection of 0.1 ppb(ng/g). Test 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 r
5、educing agent with alower limit of detection of this test method of 0.01 ppm (g/g).Test Method B was developed using caustic soda.1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its u
6、se. 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 hazardsstatements are given in Section 7 and 17.1.5 Review the current material safety data sheets (MSDS)fo
7、r detailed information concerning toxicity, first-aid proce-dures, and safety precautions.2. Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water2E 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial Chemicals3TEST METHOD AALKALIN
8、E 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 analysis.4. Significance and Use4.1 Mercury is a toxic material and is also deleterious ifpresent in caustic soda and caus
9、tic potash used in certainmanufacturing processes. It must therefore be controlled as apossible pollutant. These test methods provide a procedure formeasuring mercury in liquid and solid caustic soda and causticpotash.5. Apparatus5.1 Atomic Absorption Spectrophotometer, equipped withmounting to hold
10、 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 Washing Bottle, 125-mL, with extra-coarse frittedbubbler. The bottle has a calibration line drawn at the 60-mLmark.5.5 Ga
11、s 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 measuring and maintaining aflow rate of 1.5 standard ft3/h.NOTE 1The procedure as described in this test method employs aPerkin-Elmer
12、 Model 303 atomic absorption spectrophotometer. Any otherequivalent atomic absorption spectrophotometer may be used as well asthe many commercial instruments specifically designed for measurementof mercury by flameless atomic absorption now available. However,1These test methods are under the jurisd
13、iction of ASTM Committee E15 onIndustrial and Specialty Chemicals and is the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved Apr. 10, 2003. Published May 2003. Originallyapproved in 1975. Last previous edition approved in 1998 as E 538 98.2Annual Book of AST
14、M Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 15.05.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.variation in instrument geometry, cell length, sensitivity, and mode ofresponse measurement may require appropriate modi
15、fications of theoperating parameters.6. Reagents6.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the specifications ofthe Committee on Analytical Reagents of the American Chemi-cal Society, where such specifications are available.4Othergrades may be
16、used, provided it is first ascertained that thereagent is of sufficiently high purity to permit 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 Specifica
17、tion D 1193.6.3 Anhydrous Magnesium Perchlorate.6.4 Sodium Hydroxide 50 %Membrane grade causticsoda 50 %.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-mL beaker. Let the mixture stand for 5 min before use.This mixture is unstable
18、and should not be stored. (WarningUse goggles when preparing this solution.)6.6 Cadmium Chloride 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.
19、Thissolution must be well shaken before use. (WarningUsegoggles when preparing this solution.)6.7 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)(1mL=10mgHg)Dissolve 17.1 g
20、 of mercuric nitrate (Hg(NO3)2H2O) in100 mL of water containing 2 mL of concentrated HNO3in a1-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
21、 of H2SO4(1+4), and diluteto volume with water. Mix well.6.10 Mercury Standard Solution (1 mL = 50 ng Hg)Pipet1.0 mL of the standard mercury solution containing 50 gHg/mL into a 1-L volumetric flask, acidify with 5 mL of H2SO4(1+4), and dilute to volume with water. Mix well.6.11 Mercury Standard Sol
22、ution (1 mL = 5 ng Hg)Pipet10.0 mL of the standard mercury solution containing 50 ngHg/mL into a 100mL 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
23、.84) to 800 mL of water.This solution is dispensed from a 10-mL buret. (WarningUse goggles when preparing 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
24、 that theeyelids be held open during the flushing period. Get medicalattention immediately for any eye 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 thoroug
25、hly withwater.8.2 Connect the apparatus shown in Fig. 1 to the atomicabsorption spectrophotometer and 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.
26、All connections between glass should be made with minimum lengths ofvinyl tubing.NOTE 3The optimum flow 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 oper
27、ating conditions in accordance with thefollowing parameters and allow the spectrophotometer to warmup for at least 15 min. Select the proper scale expansion for thestandards used from Table 1. The conditions shown are for thePerkin-Elmer Model 303 (Note 1).Wavelength 253.7 nmSlit width 4 (6.5 )Lamp
28、current approximately 10 mARecorder noise suppression 2, giving approximately 90 % ofresponse in 1 sScale expansion 338.4 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 blank by adding 20 mL of 50
29、 %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 mL of water to the gas-washing bottle by slowlydelivering the water down the side of the bottle. This will layer4Reagent Chemicals, American Chemical Society
30、Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial C
31、onvention, Inc. (USPC), Rockville,MD. FIG. 1 Mercury Aeration ApparatusE 538 98 (2003)e12the water on top of the 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 conne
32、ctthe gas-washing bottle to the aeration apparatus. Turn StopcockA from the bypass to the aeration position and aerate 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
33、with as littledelay as possible between operations.8.10 An absorption peak of less than 10 % should beobtained at 33 scale expansion. Continue running blanks untilthis is achieved. Consistently higher blanks indicate a contami-nation problem from dirty glassware or reagents. Clean theapparatus with
34、aqua regia and prepare fresh reagents until asatisfactory blank is obtained.8.11 The concentration of mercury in the 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 lea
35、st three standardsin 150-mL borosilicate extraction flasks in accordance withTable 2. Analyze each standard by adding 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
36、 Convert the values for percent absorption to absor-bance using the tables in the instrument instruction manual oran optical density scale ruler. Subtract the absorbance of thereagent blank from the absorbance of each standard. Draw acalibration curve by plotting absorbance versus nanograms ofmercur
37、y. At 33 scale expansion, the readings in recorder chartdivisions are approximately equal to absorbance and may beused 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 ab
38、sorption versus concentration. A good deal of time issaved using this method of plotting a calibration curve.59. Analysis 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
39、 to the gas-washing bottle before the 50 %membrane caustic soda in 8.5. Weigh the amount of sampleadded to the gas-washing 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 th
40、e total concentration of caustic soda in thefinal solution in the gas-washing bottle at or below 25 %.9.3 Proceed with 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
41、 through the entire procedure from theabsorbance of the sample. Obtain the nanograms of mercury inthe sample from the calibration curve.10. 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 Re
42、port the parts per billion mercury to the nearest 0.01ppb.12. Precision and Bias12.1 The following criteria should be used in judging theacceptability of results (Note 5):5Harre, Gustav N., Atomic Absorption News Letter, Vol 8, No. 2, 1969.TABLE 1 Expected Range and Sample SizeTest Method AExpected
43、Range,ng/gSample Size, g Standards, ng Scale Expansion60 1 10, 50, 100 3330-60 2.5 10, 50, 100 3315-30 5 10, 50, 100 337-30 10 10, 50, 100 333-7 20 10, 50, 100 333 40 0.5, 10, 50 33Test Method BExpected Range,g/gSample Size, g Standards, g Scale Expansion0.2 to 10 2 2,5,10,20 130.01 to 0.5 5 0.2,0.5
44、,1,2 33TABLE 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 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 i
45、n 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 . . . 1.02.0 5 . . . 2.05 5 . 5.010 5 1.0 . . .20 5 2.0 . . .E 538 98 (2003)e1312.1.1 Repeatability (Single Analyst)The standard devia-tion an
46、d 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)Th
47、e laboratory precision for this testmethod has not been determined.12.1.3 Reproducibility (Multilaboratory)The reproduc-ibility for this test method has not been determined.12.2 BiasThe bias of this test method has not beendetermined due to the unavailability of suitable referencematerials.NOTE 5The
48、 preceding precision statements are based on a studyperformed in one laboratory in 1997 on 2 samples of sodium hydroxidecontaining approximately 0.07 and 0.5 ppb Hg, and 2 samples ofpotassium hydroxide containing approximately 2 and 14 ppb Hg. Oneanalyst performed 10 replicate determinations on each
49、 sample on one dayfor a total of 40 determinations.6TEST METHOD BPERMANGANATE OXIDATIONFOLLOWED BY ACIDIC REDUCING AGENT13. Summary of Test Method13.1 Mercury is converted to mercuric ion by oxidation withpotassium permanganate then reduced to metallic mercurywhich is aerated from the solution and determined by coldvapor atomic absorption analysis.14. Significance and Use14.1 Mercury is a toxic material and is also deleterious ifpresent in caustic soda used in certain manufacturing pro-cesses. It must therefore be controlled as a possible polluta
