1、Designation: E538 17E538 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
2、 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*1.1 These test methods cover the routine determination of mercury in caustic soda and caustic pota
3、sh 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 detection of 0.1 ppb (ng/g
4、). 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 of 0.01 ppm (g/g). Test
5、 Method B was developed usingcaustic soda.1.3 Review the current Safety Data Sheets (SDS) for detailed information concerning toxicity, first-aid procedures, and safetyprecautions.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this sta
6、ndard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. 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 h
7、azards statements are given in Sections 7 and 1718.1.5 Review the current Safety Data Sheets (SDS) for detailed information concerning toxicity, first-aid procedures, and safetyprecautions.1.6 This international standard was developed in accordance with internationally recognized principles on stand
8、ardizationestablished in the Decision on Principles for the Development 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 WaterD6809 Guide
9、 for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related MaterialsE180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals(Withdrawn 2009)3TEST METHOD AALKALINE REDUCING AGENT3. Summary of Test Metho
10、d3.1 All forms of mercury are reduced to metallic mercury which is aerated from the solution and determined by cold vaporatomic absorption analysis.1 These test methods are under the jurisdiction of ASTM Committee D16 on Aromatic, Industrial, Specialty and Related Chemicals and isare the direct resp
11、onsibility ofSubcommittee D16.15 on Industrial and Specialty General Standards.Current edition approved April 15, 2017July 1, 2017. Published April 2017July 2017. Originally approved in 1975. Last previous edition approved in 20082017 as E538 98 (2008). 17. DOI: 10.1520/E0538-17.10.1520/E0538-17a.2
12、For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual 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 refe
13、renced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an 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
14、users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to 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 Con
15、shohocken, PA 19428-2959. United States14. Significance and Use4.1 Mercury 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
16、 for measuring mercuryin liquid and solid caustic soda and caustic potash.5. Apparatus5.1 Atomic Absorption Spectrophotometer, equipped with mounting 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
17、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 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.
18、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-Elmer Model 303 atomic absorption spectrophotometer. Any otherequivalent atomic absorption spectrophotometer may be used as well as the many comm
19、ercial instruments specifically designed for measurement ofmercury by flameless atomic absorption now available. However, variation in instrument geometry, cell length, sensitivity, and mode of responsemeasurement may require appropriate modifications of the operating parameters.6. Reagents6.1 Purit
20、y of ReagentsUnless otherwise indicated, it is intended that all reagents shall conform to the specifications of theCommittee onAnalytical Reagents of theAmerican Chemical Society, where such specifications are available.4 Other grades maybe used, provided it is first ascertained that the reagent is
21、 of sufficiently high purity to permit its use without lessening the accuracyof the determination.6.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean Type II or III reagent waterconforming to Specification D1193.6.3 Anhydrous Magnesium Perchlorate.6.4 Sodiu
22、m 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) in a100-mL beaker. Let the mixture stand for 5 min before use. This mixture is unstable and should not be stored. (WarningUsegoggles when pre
23、paring 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 caustic soda. Cadmium hydroxide will precipitate upon the addition of the caustic soda. This solutionmust be well shaken before use. (WarningU
24、se 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. Preparefresh 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
25、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)Pipet 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 wat
26、er. 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, acidify 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
27、 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, Prepare fresh daily.4 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on
28、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), Rockville, MD.E538 17a26.12 Sulfuric Acid (1+4)Add s
29、lowly 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.)7. Hazards7.1 Sodium hydroxide, potassium hydroxide, and their solutions are extremely corrosive.Any splashes on the skin
30、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 exposures.8. Calibration8.1 Take care to avoid contamination of the apparatus with mercury. Soak all glass apparatus (pipets, beakers, and ga
31、s-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 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 freq
32、uently. 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 flow rate will vary with the geometric design of each apparatus. The flow rate should be adjusted to give the maximumabsorbance and the best
33、reproducibility without excessive foaming.8.3 Adjust the operating conditions in accordance with the following parameters and allow the spectrophotometer to warm upfor at least 15 min. Select the proper scale expansion for the standards used from Table 1. The conditions shown are for thePerkin-Elmer
34、 Model 303 (Note 1).Wavelength 253.7 nmSlit 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 the bypass position and an empty gas-washing bottle connected to
35、 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 by slowly delivering the water down the side of the bot
36、tle. 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-washing bottle to the aeration apparatus. Turn Stopcock
37、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 little delay as possible between operations.8.10 An abs
38、orption 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 regia and prepare fresh reagents until a satisfactory blan
39、k 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 three standards in 150-mLborosilicate extraction flasks i
40、n 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.FIG. 1 Mercury Aeration ApparatusE538 17a38.12 Repeat Steps 8.5 8.11 for each reagent blank and standard in order of increasing concentration.8.13 Convert the valu
41、es 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 absorbance versus nanograms of mercury. At 3 scale ex
42、pansion, 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 paper can be used to plot percentabsorption versus c
43、oncentration. 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 % caustic soda or caustic potash, is added to the gas-wa
44、shing 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-washing bottle should bereduced to keep the total conc
45、entration 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.5 Harre, Gustav N., Atomic Absorption News Letter, Vol 8, No.2, 1969.TABLE 1 Expected Range and Sample SizeTest Method AExpected Range,ng/g Sample Size,
46、 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 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
47、 SolutionsTest Method Ang Hg inStandardmL of water in gasbottlemL of 50 ng/mLHg StandardmL of 5 ng/mLHg StandardTest 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
48、.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 . . .E5
49、38 17a49.4 Convert the values for percent absorption to absorbance as described in 8.13 and 8.14. Subtract 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.10. 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 Th
