1、Designation: E649 17Standard 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 parentheses indicates
2、the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 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.1.2 This standard d
3、oes 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 hazardstatements are giv
4、en in Section 7.1.3 Review the current Safety Data Sheets (SDS) for de-tailed information concerning toxicity, first-aid procedures,handling, and safety precautions.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE180 Practice for Determining the Precision of ASTMMeth
5、ods for Analysis and Testing of Industrial and Spe-cialty Chemicals (Withdrawn 2009)3E200 Practice for Preparation, Standardization, and Storageof Standard and Reagent Solutions for Chemical Analysis3.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 hydroxide (NaOH).
6、 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 hypochlorite.
7、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 causeproblems in
8、 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 equipment to d
9、eal 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.5.2 A 10-mL
10、 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 AmericanChemi
11、cal 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 water shall
12、 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.1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct
13、responsibility ofSubcommittee D16.16 on Industrial and Specialty Product Standards.Current edition approved March 1, 2017. Published March 2017. Originallyapproved in 1978. Last previous edition approved in 2011 as E649 00 (2011).DOI: 10.1520/E0649-17.2For referenced ASTM standards, visit the ASTM w
14、ebsite, 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Reagent Chemicals, Ameri
15、can 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, U.K., and the United States Pharmacopeiaand National Formulary,
16、 U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.*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 StatesThis international standard was developed in accordance with int
17、ernationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1FIG. 1 Chlorine Gas Sampling Apparatus1. Inver
18、ted 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 water6. Evaporating coil (two loops held with tape at indicated points)7. Gas sampling apparatus of Fig. 1FIG. 2
19、Liquid Chlorine Sampling EquipmentE649 1726.4 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 hypochlorite bleach
20、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 hypochlorite bleachsolution i
21、s 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 molybdate (NH4)6Mo7
22、O244H2O) 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 ofmonobasic sodium ph
23、osphate (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 standard 0.1 N sodium th
24、iosulfate solution.Prepare, standardize, and restandardize 0.1 N sodium thiosul-fate 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 stirrin
25、g, 1 volume of concentrated sulfuric acid (sp gr1.84, H2SO4) to 5.5 volumes of water. 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. W
26、arning: 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 water. For eyes, immedi-
27、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. Personnel should beequi
28、pped 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 chlorine out of doors,pe
29、ople downwind from such operation should be warned of thepossible release of chlorine 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 abs
30、orption 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.7.5 In the event chlorine is inhaled, first aid should besummoned immediately a
31、nd 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 Record to the nearest 0.1 g the tare of the clean and drychlorine gas sampling ap
32、paratus 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 allow to stand to reach temperature equilibrium.8.2 Saturated chlorine vapor
33、will contain only about 0.3 asmuch bromine as the liquid chlorine with which it is inequilibrium. Hence, when sampling containers of liquidchlorine, it is necessary to make sure that only the liquid phaseis sampled. Gaseous chlorine sources may be sampled directly,using a small valve to control the
34、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.8.3 A satisfactory vaporizer for sampling liquid chlorine isreadily prepared from
35、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 aliquid chlorine cylinder, invert the cylinder and connect theapparatus as shown in F
36、ig. 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 liquidchlorine to the control valve.8.4 Swirl the NaOH solution in the chlorine samp
37、lingapparatus 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 sampling apparatus partially out ofits insulating jacket to observe the bubbles rising
38、 from thefritted gas sparger. As the air is purged from the system,increase the chlorine flow, so that the chlorine bubbles enteringE649 173the 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
39、 the temperature of thesolution.8.5 The temperature should rise at 2 to 5C/min. If the 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.When the temperature reaches
40、 20C above the initialtemperature, remove the sampling apparatus from the insulat-ing jacket, turn off the control valve, and immediately discon-nect the PTFE tubing from the control valve. With an aspiratorbulb, blow air through the tubing to force all chlorine in thePTFE tubing into the sample sol
41、ution.8.6 Close the chlorine supply valve and immediately openslightly the 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 andc
42、ontrol 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 solution while using theaspirator bulb to push the sample solution back and forththrough the sparger frit. Carefully clean and dry
43、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 of the empty apparatus is theweight of the sample solution.9. Procedure9.1 Take about one third of the sample solution (61 g),weigh
44、 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 (Na2SO3), and 25 mL of water, swirl, and warm, todissolve; then add slowly, while swirling, 9 mL of H2SO4(1 + 1). Add three boilin
45、g 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.The starch iodide paper should be bleached colorless, indicat-ing an excess of sulfite over the chlorine in the sample.Continue to b
46、oil 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 below 50C, add 1 drop of phenol-phthalein indicator solution, and neutralize to within 1 dropexcess of 10 % NaOH solution. Add 20 m
47、L 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 this boiling period, the steamfrom the sample solution should rapidly turn moist starchiodide paper blue. This indicates an adequate
48、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 temperature, add1gofpotassium iodide(KI), 25 mL of 6 N H2SO4, and 2 drops of molybdate solution.Immediately titrate the liberated i
49、odine 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. 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 substituting 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 solutioncons
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1