1、Designation: E538 98 (Reapproved 2008)E538 17Standard 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 o
2、r, in the case of revision, 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 Scope*1.1 These test methods cover the routine determination of mercury in causti
3、c soda and caustic potash liquors and anhydrouscaustic soda in the solid, flake, ground, and bead form by the flameless atomic absorption method.1.2 Two test methods are described as follows:Test MethodAemploys a direct analysis of the sample using an alkaline reducingagent with a lower limit of det
4、ection of 0.1 ppb (ng/g). Test Method A was developed using caustic soda and caustic potash. TestMethod B requires a preliminary neutralization of the sample followed by a permanganate oxidation before it can be analyzed byan acidic reducing agent with a lower limit of detection of this test method
5、of 0.01 ppm (g/g). Test Method B was developed usingcaustic soda.1.3 The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use
6、. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. Specific hazards statements are given in SectionSections 7 and 17.1.5 Review the current material safety data sheets (MSD
7、S) Safety Data Sheets (SDS) for detailed information concerningtoxicity, first-aid procedures, and safety precautions.1.6 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development
8、 of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE180 Practice for Determining the Precision of ASTM Methods for Analysis and Testi
9、ng of Industrial and Specialty Chemicals(Withdrawn 2009)3TEST METHOD AALKALINE REDUCING AGENT3. Summary of Test Method3.1 All forms of mercury are reduced to metallic mercury which is aerated from the solution and determined by cold vaporatomic absorption analysis.4. Significance and Use4.1 Mercury
10、is a toxic material and is also deleterious if present in caustic soda and caustic potash used in certain manufacturingprocesses. It must therefore be controlled as a possible pollutant. These test methods provide a procedure for measuring mercuryin liquid and solid caustic soda and caustic potash.1
11、 These test methods are under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons Aromatic, Industrial, Specialty and Related Chemicals and is thedirect responsibility of Subcommittee D16.15 on Industrial and Specialty General Standards.Current edition approved Dec. 15, 2008April 15, 201
12、7. Published March 2009April 2017. Originally approved in 1975. Last previous edition approved in 20032008 asE538 98 (2003).(2008). DOI: 10.1520/E0538-98R08.10.1520/E0538-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For A
13、nnual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an
14、 indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to
15、 be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Apparatus5.1 Atomic Absorption Spectrophotometer, equipped with mounting to hold
16、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 windows.5.4 Gas Washing Bottle, 125-mL, with extra-coarse fritted bubbler. The bottle has a calibration line drawn at the 60-mL mark.5.5 Ga
17、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 a flow rate of 1.5 standard ft3/h.NOTE 1The procedure as described in this test method employs a Perkin-Elm
18、er Model 303 atomic absorption spectrophotometer. Any otherequivalent atomic absorption spectrophotometer may be used as well as the many commercial instruments specifically designed for measurement ofmercury by flameless atomic absorption now available. However, variation in instrument geometry, ce
19、ll length, sensitivity, and mode of responsemeasurement may require appropriate modifications of the operating parameters.6. Reagents6.1 Purity of ReagentsUnless otherwise indicated, it is intended that all reagents shall conform to the specifications of theCommittee onAnalytical Reagents of theAmer
20、ican Chemical Society, where such specifications are available.4 Other grades maybe used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracyof the determination.6.2 Purity of WaterUnless otherwise indicated, references to
21、 water shall be understood to mean Type II or III reagent waterconforming to Specification D1193.6.3 Anhydrous Magnesium Perchlorate.6.4 Sodium Hydroxide 50 %Membrane grade caustic soda 50 %.6.5 Aqua RegiaCarefully add 10-mL of concentrated HNO3 (sp gr 1.42) to 30 mL of concentrated HCl (sp gr 1.19)
22、 in a100-mL beaker. Let the mixture stand for 5 min before use. This mixture is unstable and should not be stored. (WarningUsegoggles when preparing this solution.)6.6 Cadmium Chloride Solution (10 g/100 mL)Dissolve 10 g of cadmium chloride in 50 mL of water and then add 50 mLof 50 % membrane grade
23、caustic soda. Cadmium hydroxide will precipitate upon the addition of the caustic soda. This solutionmust be well shaken before use. (WarningUse goggles when preparing this solution.)6.7 Stannous Chloride Solution (10 g/100 mL)Dissolve 10 g of stannous chloride (SnCl22H2O) in 100 mL of water. Prepar
24、efresh once a week.6.8 Mercuric Nitrate Stock Solution (0.05M) (1 mL = 10 mg Hg)Dissolve 17.1 g of mercuric nitrate (Hg(NO3)2H2O) in 100mL of water containing 2 mL of concentrated HNO3 in a 1-L volumetric flask. Dilute to volume with water and mix well.6.9 Mercury Standard Solution (1 mL= 50 g Hg)Pi
25、pet 5.0 mLof 0.05 M mercuric nitrate stock solution into a 1-Lvolumetricflask, acidify with 5 mL of H2SO4 (1+4), and dilute to volume with water. Mix well.6.10 Mercury Standard Solution (1 mL = 50 ng Hg)Pipet 1.0 mL of the standard mercury solution containing 50 g Hg/mLinto a 1-L volumetric flask, a
26、cidify with 5 mL of H2SO4 (1+4), and dilute to volume with water. Mix well.6.11 Mercury Standard Solution (1 mL = 5 ng Hg)Pipet 10.0 mL of the standard mercury solution containing 50 ng Hg/mLinto a 100mLvolumetric flask, acidify with 5 mLof H2SO4 (1+4), and dilute to volume with water. Mix well, Pre
27、pare fresh daily.6.12 Sulfuric Acid (1+4)Add slowly while stirring 200 mL of concentrated H2SO4(sp gr 1.84) to 800 mL of water. Thissolution is dispensed from a 10-mL buret. (WarningUse goggles when preparing this solution.)4 Reagent Chemicals, American Chemical Society Specifications, American Chem
28、ical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Roc
29、kville, MD.E538 1727. Hazards7.1 Sodium hydroxide, potassium hydroxide, and their solutions are extremely corrosive.Any splashes on the skin or eyes mustbe flushed with cold water. It is important that the eyelids be held open during the flushing period. Get medical attentionimmediately for any eye
30、exposures.8. Calibration8.1 Take care to avoid contamination of the apparatus with mercury. Soak all glass apparatus (pipets, beakers, and gas-washingbottle) in aqua regia before use. Rinse thoroughly with water.8.2 Connect the apparatus shown in Fig. 1 to the atomic absorption spectrophotometer and
31、 adjust the air flow rate to 1.5 standardft3/h (see Notes 2 and 3).NOTE 2The magnesium perchlorate in the drying tube should be replaced frequently. A cork stopper should be used with the drying tube. Allconnections between glass should be made with minimum lengths of vinyl tubing.NOTE 3The optimum
32、flow rate will vary with the geometric design of each 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 the following parameters and allow the spectrophotometer to wa
33、rm upfor at least 15 min. Select the proper scale expansion for the standards used from Table 1. The conditions shown are for thePerkin-Elmer Model 303 (Note 1).WavelengthSlit widthLamp currentRecorder noise suppressionScale expansion8.4 Allow the base line to stabilize with Stopcock A in the bypass
34、 position and an empty gas-washing bottle connected to theapparatus.8.5 Prepare a reagent blank 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 the gas-washing bottle.8.7 Add 20 mL of water to the gas-washing bottle b
35、y slowly delivering the water down the side of the bottle. This will layerthe water on top of the cadmium chloride solution and minimize premature mixing of the reagents.8.8 Add 2 mL of SnCl2 solution to the gas-washing bottle delivering the solution down the side of the bottle and connect thegas-wa
36、shing bottle to the aeration apparatus. Turn Stopcock A from the bypass to the aeration position and aerate the solution.8.9 Determine the percent absorption from the peak height on the recorder chart when a constant reading is obtained.NOTE 4Steps 8.5 8.9 should be carried out in sequence with as l
37、ittle delay as possible between operations.8.10 An absorption peak of less than 10 % should be obtained at 3 scale expansion. Continue running blanks until this isachieved. Consistently higher blanks indicate a contamination problem from dirty glassware or reagents. Clean the apparatus withaqua regi
38、a and prepare fresh reagents until a satisfactory blank is obtained.8.11 The concentration of mercury in the standards should cover the expected concentration in the sample to be analyzed. Table1 suggests the standards to be prepared for various concentration levels. Prepare a series of at least thr
39、ee standards in 150-mLborosilicate extraction flasks in accordance with Table 2.Analyze each standard by adding it with the water in 8.7 and completingthe analysis as described in 8.8 to 8.9.8.12 Repeat Steps 8.5 8.11 for each reagent blank and standard in order of increasing concentration.FIG. 1 Me
40、rcury Aeration ApparatusE538 1738.13 Convert the values for percent absorption to absorbance using the tables in the instrument instruction manual or an opticaldensity scale ruler. Subtract the absorbance of the reagent blank from the absorbance of each standard. Draw a calibration curveby plotting
41、absorbance versus nanograms of mercury. At 3 scale expansion, the readings in recorder chart divisions areapproximately equal to absorbance and may be used directly as the ordinate of the calibration curve.8.14 Alternatively, in instruments where the signal is recorded in percent absorption, semilog
42、 paper can be used to plot percentabsorption versus concentration. A good deal of time is saved using this method of plotting a calibration curve.59. Analysis of Sample9.1 Select a sample size in accordance with the anticipated mercury concentration from Table 1.9.2 The sample, in the form of 50 % c
43、austic soda or caustic potash, is added to the gas-washing bottle before the 50 %membrane caustic soda in 8.5. Weigh the amount of sample added to the gas-washing bottle to the nearest 0.01 g. When largesamples of caustic soda are analyzed, the volume of 50 % membrane caustic soda added to the gas-w
44、ashing bottle should bereduced to keep the total concentration of caustic soda in the final 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 absorbance as described in 8.13 and 8.14. Subtract
45、 the absorbance of the reagentblank carried through the entire procedure from the absorbance of the sample. Obtain the nanograms of mercury in the sample fromthe calibration curve.5 Harre, Gustav N., Atomic Absorption News Letter, Vol 8, No.2, 1969.TABLE 1 Expected Range and Sample SizeTest Method A
46、Expected Range,ng/g Sample Size, g Standards, ng Scale ExpansionTest Method AExpected Range,ng/g Sample 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, 100 33 40 0.5, 10, 50 3Test Method BExpected Range,g/g Sample
47、 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 20 . . . 0.12.5 20 . . . 0.55.0 19 . . . 1.010 20 0.2 . . .
48、50 19 1.0 . . .100 18 2.0 . . .500 10 10 . . .1000 0 20 . . .Test Method Bg Hg in Standard mL of NaCl Brine mL of 10 g/mL HgStandard Solution mL 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
49、. . .E538 17410. Calculation10.1 Calculate the mercury content of the sample as follows:Hg,ppb5AB (1)where:A = mercury in sample, ng, andB = sample weight, g.11. Report11.1 Report the parts per billion mercury to the nearest 0.01 ppb.12. Precision and Bias12.1 The following criteria should be used in judging the acceptability of results (Note 5):12.1.1 Repeatability (Single Analyst)The standard deviation and coefficient of variation for a single determination has beenestimated to be the values listed in Table 3 at the indicated de
