ASTM E649-2000(2011) 3125 Standard Test Method for Bromine in Chlorine《氯气中溴含量的标准试验方法》.pdf

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1、Designation: E649 00 (Reapproved 2011)Standard Test Method forBromine in Chlorine1This standard is issued under the fixed designation E649; 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 pare

2、ntheses 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 bromine inliquid chlorine and in gaseous chlorine with a lower limit ofdetection of 4 ug/kg by weight.1.

3、2 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 hazards

4、tatements are given in Section 7.1.3 Review the current Materials Safety Data Sheets(MSDS) for detailed information concerning toxicity, first-aidprocedures, handling, and safety precautions.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE180 Practice for Determining

5、 the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals3E200 Practice for Preparation, Standardization, and Storageof Standard and Reagent Solutions for Chemical Analysis3. Summary of Test Method3.1 Chlorine gas is sampled by absorption in aqueoussodium hydroxid

6、e (NaOH). Liquid chlorine is first vaporized,and the vapor is absorbed in aqueous sodium hydroxide. Analiquot of the sample solution is reduced with an excess ofsulfite ion, acidified, and excess sulfur dioxide (SO2) boiledout. In a carefully buffered solution, bromide is oxidized tobromate by hypoc

7、hlorite. Excess hypochlorite is reduced tochloride by formate. In the presence of molybdate catalyst,bromate is reduced to bromide by iodide, and the liberatediodine is titrated with standard sodium thiosulfate solution.4. Significance and Use4.1 Low levels of bromine contaminant in chlorine causepr

8、oblems in some industrial uses. This test method may beused to determine bromine in liquid or gaseous chlorine atlevels as low as 4 ug/kg.5. Apparatus5.1 The construction of the chlorine gas sampling apparatusand of the assembled sampling equipment is shown in Figs. 1and 2. Modification of the equip

9、ment to deal with specialsampling circumstances may be necessary. In Fig. 2, thecontrol valve is shown with an adaptor for connection to achlorine cylinder valve. Other adaptors will be required whensampling liquid chlorine in liquefaction plant streams or fromlarge shipping or storage containers.5.

10、2 A 10-mL buret calibrated in 0.05-mL divisions is usedwhen titrating with 0.01 N standard sodium thiosulfate solu-tion.6. Reagents6.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents should conform to the specificationsof the Committee on Analytical Reagents of the Amer

11、icanChemical Society, where such specifications are available.4Other grades may be used, provided it is first ascertained thatthe reagent is of sufficiently high purity to permit its usewithout lessening the accuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, referencesto wa

12、ter shall be understood to mean Type II or Type IIIreagent water conforming to Specification D1193.6.3 Chloride SolutionDissolve 200 g of sodium chloride(NaCl) in 940 mL of water.6.4 Formate SolutionDissolve 50 g of sodium formate in175 mL of water.1This test method is under the jurisdiction of ASTM

13、 Committee E15 onIndustrial and Specialty Chemicals and is the direct responsibility of SubcommitteeE15.02 on Product Standards.Current edition approved Aug. 1, 2011. Published November 2011. Originallyapproved in 1978. Last previous edition approved in 2005 as E649 00 (2005)1.DOI: 10.1520/E0649-00R

14、11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical s

15、tandard is referencedon www.astm.org.4Reagent 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, BDH Ltd., Poole, Dorset,

16、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 Conshohocken, PA 19428-2959, United States.FIG. 1 Chlorine Gas Sampling Apparatus1. Inverted liquid chlorin

17、e cylinder2. Chlorine cylinder valve3. Control valve (14-in. 316 stainless steel needle valve)4.14-in. PTFE instrument air tubing5. Small pail or 2-L beaker filled with water6. Evaporating coil (two loops held with tape at indicated points)7. Gas sampling apparatus of Fig. 1FIG. 2 Liquid Chlorine Sa

18、mpling EquipmentE649 00 (2011)26.5 Hypochlorite SolutionDissolve 6.2 g of NaOH in 190mL of water and chlorinate slowly, with stirring, to give a gainin weight of 5.0 g.NOTE 1If desired, a commercial hypochlorite bleach solution may beused as the hypochlorite solution. Although such commercial bleach

19、solutions are not made from reagent grade chemicals, the reagent blankdetermination (see 9.4) corrects for the bromine and any chlorate contentin such solutions. A proprietary 5.25 % sodium hypochlorite bleachsolution is satisfactory for this use. Because the sodium chloride andhypochlorite solution

20、s contribute most to the reagent blanks, dispensethese solutions by pipet to ensure uniformity of blanks and determinations(see 9.1 and 9.2).6.6 Molybdate Solution (44 g/L)Dissolve 4.4 g of ammo-nium molybdate (NH4)6Mo7O244H2O) in 10 mL of 6 Nammonium hydroxide (NH4OH) and dilute with 90 mL ofwater.

21、6.7 Phenolphthalein Indicator Solution (1 g/L)Dissolve0.1 g of phenolphthalein and 0.1 g sodium carbonate (Na2CO3)in 5 mL of water and dilute to 100 mL.6.8 Phosphate Solution (100 g/L)Dissolve 50 g ofmonobasic sodium phosphate (NaH2PO4H2O) in 500 mL ofwater.6.9 Sodium Hydroxide Solution (10 %)Dissol

22、ve 1 part byweight of sodium hydroxide (NaOH) in 9 parts of water.6.10 Sodium Thiosulfate, Standard Solution (0.01 N)Prepare 0.01 N sodium thiosulfate solution fresh daily byaccurate dilution of standard 0.1 N sodium thiosulfate solution.Prepare, standardize, and restandardize 0.1 N sodium thiosul-f

23、ate solution in accordance with Practice E200.6.11 Starch Solution (10 g/L)Dissolve1gofsolublestarch in 100 mL of boiling water. Make up fresh daily.6.12 Sulfuric Acid (6 N)Add slowly and cautiously withconstant stirring, 1 volume of concentrated sulfuric acid (sp gr1.84, H2SO4) to 5.5 volumes of wa

24、ter. Warning: Use goggleswhen preparing this solution. Cool to room temperature beforeuse.6.13 Sulfuric Acid (1 + 1)Add slowly with stirring 1volume of concentrated sulfuric acid (H2SO4, sp gr 1.84) to 1volume of water. Warning: Use goggles when preparing thissolution.7. Hazards7.1 Concentrated sulf

25、uric acid, sodium hydroxide, and so-dium hypochlorite solutions are rapidly corrosive to skin andeyes. In case of accidental contact with skin, immediately flushaffected part with large volumes of water. For eyes, immedi-ately flush with water for at least 15 min; then get promptmedical attention. G

26、oggles should be worn when handlingthese chemicals.7.2 Chlorine sampling should be performed only by personsthoroughly familiar with handling this material and withoperation of the sampling system. Personnel should beequipped with a respirator, goggles, faceshield, and gloves. Ifpossible, perform sa

27、mpling in a hood or other well-ventilatedarea. In sampling liquid chlorine, do not leave the spacebetween two closed valves filled with liquid chlorine (see 8.6).7.3 When sampling and working with chlorine out of doors,people downwind from such operation should be warned of thepossible release of ch

28、lorine vapors.7.4 It is recommended that means be available for disposalof excess chlorine in an environmentally safe and acceptablemanner. If chlorine cannot be disposed of in a chlorine-consuming process, a chlorine absorption system should beprovided. When the analysis and sampling regimen requir

29、es aninitial purging of chlorine from a container, the purged chlorineshould be similarly handled. Purging to the atmosphere shouldbe avoided.7.5 In the event chlorine is inhaled, first aid should besummoned immediately and oxygen administered withoutdelay.7.6 Chlorine is a corrosive and toxic mater

30、ial. A well-ventilated fume hood should be used to house all test equip-ment when this product is analyzed in the laboratory.8. Sampling8.1 Record to the nearest 0.1 g the tare of the clean and drychlorine gas sampling apparatus of Fig. 1, except for theinsulating jacket.Add 150 mL of 10 % NaOH solu

31、tion and sealthe stopper firmly in place. Record the tare of this assembly tothe nearest 0.1 g. Place the apparatus in the insulating jacketand allow to stand to reach temperature equilibrium.8.2 Saturated chlorine vapor will contain only about 0.3 asmuch bromine as the liquid chlorine with which it

32、 is inequilibrium. Hence, when sampling containers of liquid chlo-rine, it is necessary to make sure that only the liquid phase issampled. Gaseous chlorine sources may be sampled directly,using a small valve to control the chlorine flow. Feed the liquidchlorine through vaporizing equipment before pa

33、ssing theresulting vapor into the chlorine gas sampling apparatus. Thereis no need for a vaporizer when sampling a source of gaseouschlorine.8.3 A satisfactory vaporizer for sampling liquid chlorine isreadily prepared from a 1.5 to 2-m length of14-in. (6.35-mm)outside diameter polytrafluoroethylene

34、(PTFE) instrument airtubing. This had adequate flexibility, and is easily coiled toform a 120-mm diameter evaporating coil. When sampling aliquid chlorine cylinder, invert the cylinder and connect theapparatus as shown in Fig. 2. Do not wire the tubing connec-tions. This will allow the tube to blow

35、off in case of excessivepressure. With the small control valve closed, open the liquidchlorine supply valve about a half turn to bring the liquidchlorine to the control valve.8.4 Swirl the NaOH solution in the chlorine samplingapparatus thoroughly and note the initial temperature; thenvery carefully

36、 open the control valve to allow a small stream ofchlorine gas to purge the air from the line leading to thesampling apparatus. Lift the sampling apparatus partially out ofits insulating jacket to observe the bubbles rising from thefritted gas sparger. As the air is purged from the system,increase t

37、he chlorine flow, so that the chlorine bubbles enteringthe solution from the sparger shrink to minimum size about 20mm below the surface of the liquid. Lower the sampling bottleinto the insulating jacket and observe the temperature of thesolution.8.5 The temperature should rise at 2 to 5C/min. If th

38、e rateof temperature rise is higher or lower than this, adjust thechlorine flow accordingly. Swirl the sampling apparatus fre-quently to mix thoroughly and achieve temperature uniformity.E649 00 (2011)3When the temperature reaches 20C above the initial tempera-ture, remove the sampling apparatus fro

39、m the insulating jacket,turn off the control valve, and immediately disconnect thePTFE tubing from the control valve. With an aspirator bulb,blow air through the tubing to force all chlorine in the PTFEtubing into the sample solution.8.6 Close the chlorine supply valve and immediately openslightly t

40、he control valve to vent liquid chlorine trappedbetween the valves. Direct the vented chlorine into a hood or achlorine disposal system. Warning: Do not overlook thisventing procedure. If the space between the closed supply andcontrol valves is left completely filled with liquid chlorine,dangerous p

41、ressures rapidly build up when the temperature isallowed to rise.8.7 Thoroughly blend the sample solution while using theaspirator bulb to push the sample solution back and forththrough the sparger frit. Carefully clean and dry the outside ofthe sampling assembly and weigh to the nearest 0.1 g. The

42、gainin weight of the apparatus is the weight of chlorine absorbed.The final weight less the tare of the empty apparatus is theweight of the sample solution.9. Procedure9.1 Take about one third of the sample solution (61 g),weigh to the nearest 0.1 g, and transfer into a 500-mLErlenmeyer flask with a

43、 volume calibration mark at 100 mL.Add by pipet, 25 mL of chloride solution, add9gofsodiumsulfite (Na2SO3), and 25 mL of water, swirl, and warm, todissolve; then add slowly, while swirling, 9 mL of H2SO4(1 + 1). Add three boiling beads, heat to boiling, and immedi-ately test the vapor with moist sta

44、rch iodide paper that has beentreated with a trace of chlorine vapor to give a light blue color.The starch iodide paper should be bleached colorless, indicat-ing an excess of sulfite over the chlorine in the sample.Continue to boil for 10 min, adding water if necessary to bringany deposited salts in

45、to solution. At this point, the solutionvolume should be less than 100 mL.9.2 Cool the sample to below 50C, add 1 drop of phenol-phthalein indicator solution, and neutralize to within 1 dropexcess of 10 % NaOH solution. Add 20 mL of phosphatesolution, and add by pipet, 10 mL of hypochlorite solution

46、.Heat the solution nearly to boiling for 5 min, then boil thesolution for 2 min. At the end of this boiling period, the steamfrom the sample solution should rapidly turn moist starchiodide paper blue. This indicates an adequate excess ofhypochlorite in the sample.9.3 Slowly add 10 mL of the formate

47、solution whileswirling. Wash down the flask and again bring the solution toboiling. Cool to room temperature, add1gofpotassium iodide(KI), 25 mL of 6 N H2SO4, and 2 drops of molybdate solution.Immediately titrate the liberated iodine with standard 0.01 Nsodium thiosulfate solution until the sample s

48、olution is paleyellow. Add 2 mL of starch solution and titrate until the bluecolor disappears. Record the volume of thiosulfate consumed(A mL).NOTE 2Titrate samples that turn very dark from liberation of largeamounts of iodine with 0.1 N thiosulfate solution.9.4 Run a blank determination substitutin

49、g 50 mL of 10 %NaOH solution for the weighed aliquot of sample solution. Use17 mL of H2SO4(1 + 1) rather than the 9 mL used with thesample. Record the volume of 0.01 N thiosulfate solutionconsumed (B mL).NOTE 3The blank determination is necessary so that correction can bemade for the traces of bromine normally present in reagent grade sodiumchloride and in hypochlorite solutions. The blank determination alsomakes correction for small concentrations of chlorate that hypochloritesolutions may also contain.10. Calculation10.1 To determine the mass of chlorine