ASTM E649-2000(2005)e1 Standard Test Method for Bromine in Chlorine《氯中溴含量的标准试验方法》.pdf

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1、Designation: E 649 00 (Reapproved 2005)e1Standard Test Method forBromine in Chlorine1This standard is issued under the fixed designation E 649; 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

2、parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes were made in June 2005.1. Scope1.1 This test method covers the determination of bromine inliquid chlorine and in gaseous chlorine wi

3、th a lower limit ofdetection of 4 ug/kg by weight.1.2 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 r

4、egulatory limitations prior to use. Specific hazardstatements 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:2D 1193 Specifi

5、cation for Reagent WaterE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial ChemicalsE 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis3. Summary of Test Method3.1 Chlorine gas is sampled

6、 by absorption in aqueoussodium hydroxide (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

7、, bromide is oxidized tobromate by hypochlorite. 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

8、 bromine contaminant in chlorine causeproblems 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

9、 Figs. 1and 2. Modification of the equipment 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 fro

10、mlarge shipping or storage containers.5.2 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 Comm

11、ittee on Analytical Reagents of the AmericanChemical Society, where such specifications are available.3Other 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 WaterUnl

12、ess otherwise indicated, referencesto water shall be understood to mean Type II or Type IIIreagent water conforming to Specification D 1193.6.3 Chloride SolutionDissolve 200 g of sodium chloride(NaCl) in 940 mL of water.1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial C

13、hemicals and is the direct responsibility of Subcommittee E15.02 onProduct Standards.Current edition approved April 1, 2005. Published May 2005. Originallyapproved in 1978. Last previous edition approved in 2000 as E 649 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcont

14、act ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of

15、 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 Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive,

16、PO Box C700, West Conshohocken, PA 19428-2959, United States.6.4 Formate SolutionDissolve 50 g of sodium formate in175 mL of water.6.5 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 h

17、ypochlorite bleach solution may beused as the hypochlorite solution. Although such commercial bleachsolutions 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 hypochlori

18、te bleachsolution is satisfactory for this use. Because the sodium chloride andhypochlorite solutions 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

19、molybdate (NH4)6Mo7O244H2O) in 10 mL of 6 Nammonium hydroxide (NH4OH) and dilute with 90 mL ofwater.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 of

20、monobasic sodium phosphate (NaH2PO4H2O) in 500 mL ofwater.6.9 Sodium Hydroxide Solution (10 %)Dissolve 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 stand

21、ard 0.1 N sodium thiosulfate solution.Prepare, standardize, and restandardize 0.1 N sodium thiosul-fate solution in accordance with Practice E 200.6.11 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

22、withconstant stirring, 1 volume of concentrated sulfuric acid (sp gr1.84, H2SO4) to 5.5 volumes of water. Caution: 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)

23、to 1volume of water. Caution: Use goggles when preparing thissolution.7. Hazards7.1 Concentrated sulfuric 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 wa

24、ter. For eyes, immedi-ately flush with water for at least 15 min; then get promptmedical attention. Goggles 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. P

25、ersonnel should beequipped with a respirator, goggles, faceshield, and gloves. Ifpossible, perform sampling 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 ch

26、lorine out of doors,people downwind from such operation should be warned of thepossible release of chlorine vapors.FIG. 1 Chlorine Gas Sampling ApparatusE 649 00 (2005)e127.4 It is recommended that means be available for disposalof excess chlorine in an environmentally safe and acceptablemanner. If

27、chlorine cannot be disposed of in a chlorine-consuming process, a chlorine absorption system should beprovided. When the analysis and sampling regimen requires aninitial purging of chlorine from a container, the purged chlorineshould be similarly handled. Purging to the atmosphere shouldbe avoided.7

28、.5 In the event chlorine is inhaled, first aid should besummoned immediately and oxygen administered withoutdelay.7.6 Chlorine is a corrosive and toxic material. 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 Rec

29、ord 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 solution and sealthe stopper firmly in place. Record the tare of this assembly tothe nearest 0.1 g. Place the apparatus in the insulating jacketand

30、 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 is inequilibrium. Hence, when sampling containers of liquid chlo-rine, it is necessary to make sure that only the liquid phase issampled. Gase

31、ous chlorine sources may be sampled directly,using a small valve to control the chlorine flow. Feed the liquidchlorine through vaporizing equipment before passing theresulting vapor into the chlorine gas sampling apparatus. Thereis no need for a vaporizer when sampling a source of gaseouschlorine.8.

32、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 (PTFE) instrument airtubing. This had adequate flexibility, and is easily coiled toform a 120-mm diameter evaporating coil. When sampling aliqu

33、id 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 off in case of excessivepressure. With the small control valve closed, open the liquidchlorine supply valve about a half turn to bring the liqu

34、idchlorine to the control valve.8.4 Swirl the NaOH solution in the chlorine samplingapparatus thoroughly and note the initial temperature; thenvery carefully open the control valve to allow a small stream ofchlorine gas to purge the air from the line leading to thesampling apparatus. Lift the sampli

35、ng apparatus partially out ofits insulating jacket to observe the bubbles rising from thefritted gas sparger. As the air is purged from the system,increase the chlorine flow, so that the chlorine bubbles enteringthe solution from the sparger shrink to minimum size about 20mm below the surface of the

36、 liquid. Lower the sampling bottleinto the insulating jacket and observe the temperature of thesolution.1. Inverted liquid chlorine 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 w

37、ater6. Evaporating coil (two loops held with tape at indicated points)7. Gas sampling apparatus of Fig. 1FIG. 2 Liquid Chlorine Sampling EquipmentE 649 00 (2005)e138.5 The temperature should rise at 2 to 5C/min. If the rateof temperature rise is higher or lower than this, adjust thechlorine flow acc

38、ordingly. Swirl the sampling apparatus fre-quently to mix thoroughly and achieve temperature uniformity.When the temperature reaches 20C above the initial tempera-ture, remove the sampling apparatus from the insulating jacket,turn off the control valve, and immediately disconnect thePTFE tubing from

39、 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 the control valve to vent liquid chlorine trappedbetween the valves. Direct the vented chlorine int

40、o a hood or achlorine disposal system. Caution: Do not overlook thisventing procedure. If the space between the closed supply andcontrol valves is left completely filled with liquid chlorine,dangerous pressures rapidly build up when the temperature isallowed to rise.8.7 Thoroughly blend the sample s

41、olution 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 gainin weight of the apparatus is the weight of chlorine absorbed.The final weight less the tare o

42、f 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 volume calibration mark at 100 mL.Add by pipet, 25 mL of chloride solution, add9gofsodiumsulfite

43、(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 starch iodide paper that has beentreated with a trace of chlorine vapor to give a light blue color.Th

44、e 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 into solution. At this point, the solutionvolume should be less than 100 mL.9.2 Cool the sample to b

45、elow 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.Heat the solution nearly to boiling for 5 min, then boil thesolution for 2 min. At the end of thi

46、s 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 solution whileswirling. Wash down the flask and again bring the solution toboiling. Cool to room t

47、emperature, 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 solution is paleyellow. Add 2 mL of starch solution and titrate until the bluecolor disappears. Rec

48、ord 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 substituting 50 mL of 10 %NaOH solution for the weighed aliquot of sample solution. Use17 mL of H2SO4(1 + 1)

49、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 in the aliquot, usethe following equation:grams Cl2absorbed 3 grams sample aliquotgrams total samp