1、Designation: E 256 98 (Reapproved 2003)e1Standard Test Method forChlorine in Organic Compounds by Sodium Peroxide BombIgnition1This standard is issued under the fixed designation E 256; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTEWarning notes were editoria
3、lly moved into the standard text in May 2003.1. Scope1.1 This test method covers the determination of chlorine inorganic compounds by sodium peroxide bomb ignition. It isintended for application to samples of organic materials con-taining more than 0.5 % chlorine. The procedure assumes thatcompounds
4、 containing halogens other than chlorine will not bepresent.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-b
5、ility of regulatory limitations prior to use. For specific safetyprecautions, see 6.5.2, Section 7, 8.3, and 8.9.1.3 Review the current Material Safety Data Sheets (MSDS)for detailed information concerning toxicity, first aid proce-dures, and safety precautions.NOTE 1Other test methods based on oxyg
6、en bomb combustion foranalysis for chlorine are described in Test Method D 808, Test MethodD 2361, and Test Method D 4208.2. Referenced Documents2.1 ASTM Standards:D 808 Test Method for Chlorine in New and Used Petro-leum Products (Bomb Method)2D 1193 Specification for Reagent Water3D 2361 Test Meth
7、od for Chlorine in Coal4D 4208 Test Method for Total Chlorine in Coal by theOxygen Bomb Combustion/Ion Selective ElectrodeMethod4E 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals5E 200 Practice for Preparation, Standardization
8、, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis53. Summary of Test Method3.1 The sample is heated in a closed bomb with sodiumperoxide in the presence of an accelerator (potassium nitrate)and an oxygen-bearing compound (sucrose). The chlorine isconverted to chloride. The conten
9、ts of the bomb are dissolvedin water. The solution is acidified and the chloride is deter-mined by titrating the excess of silver nitrate solution used toprecipitate the chloride.4. Significance and Use4.1 This test method may be used to determine the totalchlorine content of unknown organic samples
10、 or to assayknown chlorine containing organic compounds.4.2 This test method may be used on organic materials inwhich the complete conversion to chloride can be accom-plished by sodium peroxide bomb ignition, and which containno other halogens.5. Apparatus5.1 Sodium Peroxide Bomb,6flame ignition typ
11、e, 22-mLcapacity. This consists of a 99 % nickel fusion cup, 99 % nickelcap cover, lead gaskets, a bomb body, a screw cap, a wrench,an ignition housing, a bomb socket, glass mixing rod, and a1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty Chemicals and is
12、 the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved Apr. 10, 2003. Published May 2003. Originallyapproved in 1965. Last previous edition approved in 1998 as E 256 98.2Annual Book of ASTM Standards, Vol 05.01.3Annual Book of ASTM Standards, Vol 11.01.4Annual
13、 Book of ASTM Standards, Vol 05.06.5Annual Book of ASTM Standards, Vol 15.05.6The sole source of supply of the ignition bomb and assembly known to thecommittee at this time is Parr Instrument Co., Moline, IL. The 22-mL fusion cup ispart No. N-200. If you are aware of alternative suppliers, please pr
14、ovide thisinformation to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee1, whichyou may attend.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.sodiu
15、m peroxide measuring dipper. A less expensive nickel-plated brass cap cover may be substituted.5.2 Safety ShieldAny heavy-duty commercially availableshield should suffice to confine the results of an explosion inthe event of bomb body rupture during flame ignition.5.3 Burner, blast-type, using gas a
16、nd air. For some bombwork, the cheaper bunsen burner has been found to besatisfactory.5.4 Capsules, gelatin, size No. 00, for liquid samples.6. Reagents6.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the specifications ofthe Committee on Analytical
17、Reagents of the American Chemi-cal Society, where such specifications are available.7Othergrades may be used, provided it is first ascertained that thereagent is of sufficiently high purity to permit its use withoutlessening the accuracy of the determination.6.2 Purity of WaterUnless otherwise indic
18、ated, referencesto water shall be understood to mean Type II or Type IIIreagent water conforming to Specification D 1193.6.3 Ammonium Thiocyanate, Standard Solution (0.1 N)Prepare in accordance with Practice E 200.6.4 Ferric Ammonium Sulfate Indicator Solution (80 g/L)Prepare in accordance with Prac
19、tice E 200.6.5 Mixture, Bomb Accelerator:6.5.1 Dry 900 g of potassium nitrate (KNO3) crystals in a110 to 120C oven for 2 days. Grind the dried crystals to apowder.6.5.2 Dry 300 g of granulated sucrose in a 50 to 60C ovenfor 2 days. Grind the dried sugar to a powder (WarningDonot grind potassium nitr
20、ate with sugar. To avoid the possibilityof an explosion, grind these materials separately.).6.5.3 Mix the powdered KNO3and powdered sugar in a ballmill for 20 to 30 min. Balls should be omitted from the millduring this blending operation. Store in a closed jar kept in adesiccator.6.6 Nitric Acid (sp
21、 gr 1.42)Concentrated nitric acid(HNO3).6.7 NitrobenzeneThe use and disposal of nitrobenzenemust be done in accordance with its hazardous properties (see7.2). Benzyl alcohol may be a safer, but less effective,coagulant than nitrobenzene.6.8 Silver Nitrate, Standard Solution (0.1 N)Prepare inaccordan
22、ce with Practice E 200.6.9 Sodium Peroxide, 30- to 40-mesh, calorific grade. Seethe safety precautions on the label concerning this stronglycaustic oxidant.7. Safety Precautions7.1 This test method should not be applied to samplescontaining appreciable amounts of water (0.1 % or greater).Water react
23、s spontaneously with sodium peroxide and maycause premature reaction of the sample and peroxide. Also,oxygen is released which may develop dangerously highinternal bomb pressure.7.2 Nitrobenzene is very hazardous when absorbed throughthe skin or when its vapor is inhaled. Do not get nitrobenzenein t
24、he eyes, on the skin, or on clothing. Avoid breathing itsvapor. Use only with adequate ventilation.7.3 Sodium peroxide is a potentially dangerous chemical.Avoid scattering the reagent or leaving the container exposedto the air or moisture. Spilled sodium peroxide should bewashed down with large amou
25、nts of water, and not wiped upwith paper or cloth.7.4 Fusion cups may develop holes or cracks at any time(even when relatively new, but especially after long andcontinued use) and should be examined before use; cups notsuitable for use should be discarded promptly. Fusion cupcover gaskets must be re
26、placed when damaged. Bomb bodiesand screw caps must be discarded when the threads becomeworn. This must be checked frequently.7.5 Samples of unknown or unfamiliar composition orsamples suspected of containing water or other materialreactive with sodium peroxide should be tested before mixingwith sod
27、ium peroxide. Place sodium peroxide in an emptyfusion cup to a depth of 5 mm. Cautiously (wear gloves andsafety glasses) add small quantities (approximately 25 mg) ofthe sample and mix. If the sample ignites spontaneously uponcontact with the sodium peroxide, use a gelatin capsule forweighing the sa
28、mple and introducing it into the bomb mixture.If the sample does not react with sodium peroxide, thenproceed with the weighing of the sample, omitting the use of agelatin capsule.8. Procedure8.1 Weigh (to the nearest 0.0001 g) a sample containing theequivalent of 0.1 g of chlorine. In any case, do n
29、ot exceed asample weight of 0.5 g. Solid samples should be pulverizedbefore weighing. Liquid samples and samples that react oncontact with sodium peroxide (see 7.4) should be weighed in agelatin capsule.8.2 Weigh approximately 1.0 g of KNO3-sugar mixture (see6.5) into a clean, dry fusion cup. Add on
30、e dipper (approxi-mately 15 g) of sodium peroxide to the fusion cup and mix thecontents with a clean, dry, glass stirring rod.8.3 Transfer approximately one half of the mixture momen-tarily from the fusion cup above into a second fusion cup(WarningDuring the following charging procedure, theanalyst
31、should be prepared for a premature ignition. The use ofgloves, safety spectacles, and a protective shield is urged.).Place the weighed sample (see 8.1) into the first fusion cup. Inthe case of a sample that is not in a capsule, stir the contents ofthe first cup with a clean, dry, glass rod while slo
32、wly returningthe balance of the peroxide-accelerator mixture from thesecond cup. Wipe the lower part of the rod with a 15 by 30-mmpiece of dry filter paper. Add the paper to the contents of thefusion cup and proceed promptly to the assembly operation. Inthe case of a sample that is in a capsule, ret
33、urn the balance ofthe peroxide-accelerator mixture to the first fusion cup.Promptly assemble the bomb with a gasket, cover, bomb body,7Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the Am
34、erican 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.E 256 98 (2003)e12and screw cap. Tighten the screw cap first by hand (weargloves) a
35、nd then with the wrench, supporting the bomb in thebench socket. Proceed promptly to the next step.8.4 Place the bomb on a tripod behind a safety shield. About1 or 2 mL (avoid excess) of water may be placed in thereservoir formed on top of the bomb by the surrounding screwcap. Adjust the blast burne
36、r to produce a narrow, hot flamestriking the bottom of the bomb. Do not expose anyone topossible injury should the bomb explode. Heat the bomb untilthe contents are ignited, as indicated by the boiling of the wateror a slightly perceptible dull red heat or an audible click. Ifpossible, do not contin
37、ue to heat after the water has evaporatedto dryness, as the top of the bomb will overheat and destroy thegasket. If the water does not boil, allow the bomb to heat for 7or 8 min or until the water has evaporated.8.5 Following ignition, drop the bomb into a water bath(shielded) to cool. Remove the bo
38、mb from the water bath andrinse the outside of the bomb with water.8.6 Disassemble the bomb, carefully remove the cover fromthe fusion cup, and rinse the cover with water into a 250-mLbeaker. Add sufficient water to make a volume approximately50 mL. Place the fusion cup upright in the beaker. Turn t
39、he cupon its side with a stirring rod and immediately cover with awatch glass. Allow to stand until effervescence ceases. Thefusion mass should be examined for evidence of a poor fusion,such as the presence of carbon or unfused peroxide granules, orboth. Poor fusions cause results to be low.8.7 Heat
40、 the contents of the beaker, if necessary, to dissolvethe peroxide melt. Rinse the watch glass and the fusion cupwith warm water and remove. Collect the rinsings in thebeaker.8.8 Cautiously acidify by adding HNO3(sp gr 1.42) to thebeaker while stirring. When the solution approaches neutral-ization,
41、as indicated by a decrease in effervescence, place apiece of blue litmus paper in the solution. Slowly continue theaddition of the acid until the litmus paper turns red, and thenadd 2 to 3 mL excess.8.9 Cool the solution to room temperature and transfer itcompletely to a conical 250-mL flask provide
42、d with a glassstopper. Add 1 to 2 mL of ferric ammonium sulfate indicatorsolution and 4 to 5 mL of nitrobenzene (WarningNitrobenzene is very hazardous when absorbed through theskin or when its vapor is inhaled. Do not get nitrobenzene inthe eyes, on the skin, or on clothing. Avoid breathing its vapo
43、r.Use only with adequate ventilation.).8.10 Fill a calibrated 10-mL buret to the zero mark with 0.1N NH4SCN solution. Add a few drops from the buret to theflask. Proceed to the next step.8.11 Fill a calibrated 50-mL buret to the zero mark with 0.1N AgNO3solution. Titrate the contents of the flask wi
44、th theAgNO3solution to a colorless end point. Add about 3 mLexcess and then record the total volume of AgNO3solutionadded, V1.8.12 Stopper the flask and shake vigorously for about 20 s tocoagulate the AgCl and to form a protective coating on theprecipitate. Rinse the stopper into the flask with wate
45、r.8.13 Continue the titration from the buret containing theNH4SCN solution. The end point is characterized by the firstpersistent reddish-brown color. It should remain colored duringvigorous shaking for 50 to 60 s. Record the total volume ofNH4SCN solution used, V2.8.14 BlankFor the blank, measure t
46、he specified amount ofsodium peroxide and accelerator into a bomb cup. If a gelatincapsule was used, add an empty capsule to the cup. Proceedaccording to the foregoing method.9. Calculation9.1 Calculate the chlorine content as follows:Chlorine, wt. % 5X 2 Y! 3 3.545W(1)where:X =V1N1V2N2,Y =v1N1v2N2,
47、V1= AgNO3solution used in the sample, mL,V2=NH4SCN solution used in the sample, mL,v1= AgNO3solution used in the blank, mL,v2=NH4SCN solution used in the blank, mL,N1= normality of the AgNO3solution,N2= normality of the NH4SCN solution,W = sample used, g, and3.545 = (atomic wt of chlorine 3 100)/100
48、0.10. Report10.1 Report the percentage of chlorine to the nearest0.01 %.11. Precision and Bias11.1 For Samples in CapsuleThe following criteriashould be used in judging the acceptability of results (Note 2):11.1.1 Repeatability (Single Analyst)The standard devia-tion for a single determination has b
49、een estimated to be0.261 % absolute at 14 DF. The 95 % limit for the differencebetween two such runs is 0.73 % absolute.11.1.2 Laboratory Precision (Within-Laboratory, Between-Days Variability)The standard deviation of results (eachthe average of duplicates), obtained by the same analyst ondifferent days, has been estimated to be 0.405 % absolute at 7DF. The 95 % limit for the difference between two suchaverages is 1.13 % absolute.11.1.3 Reproducibility (Multilaboratory)The standarddeviation of results (each the average of duplicates), obtainedby analysts in di
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