ASTM D4795 - 94(2008) Standard Test Method for Nitrogen Content of Soluble Nitrocellulose—Alternative Method .pdf

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1、Designation: D4795 94 (Reapproved 2008)Standard Test Method forNitrogen Content of Soluble NitrocelluloseAlternativeMethod1This standard is issued under the fixed designation D4795; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t

2、he 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. Scope1.1 Test Methods D301 for measuring nitrogen content innitrocellulose by nitrometer are the accepted standard.H

3、owever, the glassware is specialized and the precision isdependent on the development of a high level of skill by theoperator. The ferrous-sulfate titration of nitrate is a classicalprocedure. By controlling critical variables and automating theactual titration, precision equivalent to the nitromete

4、r can beachieved with nitrocellulose. This test method describes such aprocedure.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated wi

5、th 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. For specific hazardstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D301 Test Methods fo

6、r Soluble Cellulose Nitrate (With-drawn 2011)3D1193 Specification for Reagent Water3. Summary of Test Method3.1 A weighed specimen of nitrocellulose is dissolved insulfuric acid and titrated automatically with ferrous sulfate.The nitrogen content of the specimen is calculated using theequivalence fa

7、ctor of the ferrous sulfate.4. Significance and Use4.1 This test method provides a simpler means for measur-ing the nitrogen content of nitrocellulose than the nitrometerdescribed in Test Methods D301. Under controlled conditions,the procedure described is capable of results equivalent tothose obtai

8、ned by the nitrometer.5. Interferences5.1 The presence of moisture (or other volatile components)in the specimen will affect results. It is recommended that onlythoroughly dry specimens be used.5.2 Temperature rise must be controlled during the titration.The cooling bath provides that control. Howev

9、er, if the rate oftitrant addition is too fast, temperature may rise out of control.Results may then be erratic. Adherence to the procedure willavoid temperature excursions. For optimum system efficiency,room temperature should be maintained at 23 6 2C.5.3 The strength of the sulfuric acid used to d

10、issolve thespecimen is very important. Too low an acid strength slows therate of solution which, in turn, causes titrations to be abnor-mally slow. Results then become erratic.6. Apparatus6.1 Acid Bottle Safety Dispenser.6.2 Brinkman 20 Titration System, or equivalent, with 25mL amber buret:6.2.1 El

11、ectrode, platinum.6.2.2 Electrode, glass.6.3 Desiccator, with drying agent.6.4 Weighing bottles, 12-mL capacity, aluminum (preferred)or glass.6.5 Analytical Balance, accurate to 60.1 mg.6.6 Ovens135C, for drying standards, and 100C, fordrying specimens, having unexposed heating elements and thedoor

12、latch removed.6.7 Circulating Unit, for chilled water, 5 6 2C.6.8 Blender, with 0.25-L (8-oz) blender jar.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.36 on Cellulose an

13、d Cellulose Derivatives.Current edition approved June 1, 2008. Published June 2008. Originallyapproved in 1988. Last previous edition approved in 2003 as D4795 94 (2003).DOI: 10.1520/D4795-94R08.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at

14、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke

15、n, PA 19428-2959. United StatesNOTICE: This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International (www.astm.org) for the latest information17. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicat

16、ed, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permi

17、t its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type III of Specification D1193.7.3 Sulfuric Acid (H2SO4)95to98%.7.4 Ferrous Sulfate SolutionDissolve 350 g of ferrous

18、sulfate crystals (FeSO4) in 1000 mL of distilled water. Add1000 mL of 1+1 H2SO4solution. Makes 2 L.7.5 Potassium Nitrate (KNO3) Standard or an equivalentnitrate primary standard.7.6 Nitrocellulose StandardA sample with a known nitro-gen value or other known organic nitrate.8. Hazards8.1 Since the sa

19、mple of nitrocellulose must be dried, it isimperative that care be exercised in storage, handling, anddisposal. Dry nitrocellulose is extremely flammable. Refer tothe Procedure section for Drying Samples of Test MethodsD301.8.2 Strong sulfuric acid used as the solvent for the specimencan burn the sk

20、in. The ferrous sulfate titrant is also stronglyacidic. Take proper precautions to protect the operator and theequipment.8.3 To prevent burns from acid dripping off the electrodesand dispenser tip, always wipe the electrodes and dispenser tipwith a tissue before reaching under them to retrieve a bea

21、ker.9. Preparation of Apparatus9.1 If the system has been down for at least 8 h, purge thesystem with 40 mL of ferrous sulfate solution.10. Calibration and Standardization10.1 Weigh a sample bottle containing 0.5000 6 0.05 g ofKNO3that has been dried in a 135C oven for a minimum of4 h and stored in

22、a dessicator. If KNO3has been out of the ovenfor4hormore, redry in a 135C oven for a minimum of 2 h.(Nitrocellulose specimens are dried in a 100C oven for aminimum of 1 h. If out of the oven more than 2 h, redry for12 h.) Turn on the pump of the chilled water circulator to startwater flowing through

23、 the cooling bath.10.2 Place the magnetic stirring bar into a dry 250-mLbeaker and fill the beaker with 150 mL of H2SO4(20 6 2C).10.3 Place the beaker in the cooling bath on the stirrer unit.Start the stirrer and adjust the speed for a slight vortex. Toovigorous a vortex can cause the nitrocellulose

24、 to splash ontothe sides of the beaker.10.4 With the stirrer operating and the electrodes up in theair away from the acid, slowly pour the specimen into thevortex of the swirl. Be careful not to touch the dispensing tipor electrodes with the weighing bottle. Reweigh the weighingbottle to find the we

25、ight of the standard by difference.10.5 Allow most of the KNO3to dissolve. Visually inspectthe solution until no more chunks or chips of KNO3remain.The solution may be cloudy.10.6 Lower the electrodes and the dispensing tip into theH2SO4.10.7 Set the controls to the desired settings.10.8 As the KNO3

26、dissolves and HNO3is formed by thereaction of H2SO4and the specimen, a millivolt potentialchange is evident by a rising recorder pen.10.8.1 When the pen shows a leveling off, it is an indicationthat the majority of the KNO3is in solution. Visually inspectthe solution to verify the fact that chips ar

27、e no longer present.10.9 Set the buret control to a rate of about 5 mL/min.Allow10 6 0.1 mL to dispense at this rate.10.10 Stop the buret, switch the dispense-rate switch toautomatic, and restart. Allow the titration to proceed automati-cally to the end point.10.11 At the completion of the automatic

28、 titration, immedi-ately record the millilitre reading. Switch the electrode settingto STANDBY.10.12 Raise the electrodes from the acid and allow most ofthe acid to drip into the titration beaker. Carefully wipe bydabbing the electrodes and dispensing tip with a tissue.(WarningSee Section 8.) Discar

29、d the tissue into a containerof water. DO NOT allow acid to drip into the circulating-bathwater.10.13 Remove the completed titration beaker from thecooling bath.10.14 Lower the electrodes and pipet into a beaker of cleanH2SO4for soaking. Make sure the acid is not contaminatedwith FeSO4. (It may blee

30、d from the dispenser tip giving areddish tint to the acid.) Replace with clean H2SO4if thisoccurs.NOTE 1It is important to soak the electrodes in between each analysisand while the titrators are not in use. Cleanliness of equipment is of theutmost importance in this method of analysis.10.15 Calculat

31、e the nitrogen equivalence factor F for thestandard KNO3as follows:F 5 A 313.855!/B (1)where:A = weight of KNO3,g,4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Soci

32、ety, 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.D4795 94 (2008)213.855 = nitrogen equivalence of nitrogen in KNO3or in thestandard material used, andB

33、= amount of FeSO4used to titrate KNO3, mL.11. Specimen Preparation11.1 Cutting:11.1.1 Use a sample size of approximately 2 heapingtablespoons of wet nitrocellulose.11.1.2 For high viscosity types, place the sample into asmall 0.25-L (8-oz) plastic blender jar. Fill to the fill line withtap water, an

34、d screw on the cap with a 4-blade cutter unitinside.11.1.3 Place on the blender base and blend for 7 min at highspeed.11.1.4 For 11 % nitrogen and low viscosity types, grind in atissue disintegrator using a 0.5-L (16-oz) glass jar about34 fullof tap water.11.1.5 Grind each sample at high speed for t

35、heir respectivetimes as follows:Hercules Designation Time, minSS, all 5RS12 4RS14 4RS18 3AS, all 311.2 At the completion of cutting, remove the samplecontainer and draw off the excess water from the nitrocelluloseby filtering on a Bchner funnel through a circular filter paper.11.3 Dry the material i

36、n accordance with the paragraph onsmall quantities in the Procedure section for Drying Samples ofTest Methods D301.11.4 After drying, weigh 3 replicate specimens of 0.4500 60.0075 g each into a weighing can or bottle.11.5 It is desirable to analyze the specimens as soon as theyare taken out of the o

37、ven. Allow time for cooling in adesiccator before weighing. If specimens are out of the ovenfor more than 2 h, redry for12 h at 100C.12. Procedure12.1 Prepare specimens in accordance with Section 11.12.2 Repeat 10.1-10.15, using the settings for the specimengiven in Table 1.12.3 Dispose of any exces

38、s H2SO4standard down the sinkand rinse with large quantities of water.13. Calculation13.1 Calculate the percent of nitrogen N as follows:N 5 C 3 F!/D (2)where:C = FeSO4to titrate specimen, mL,F = equivalence factor from 10.15, andD = weight of specimen, g.14. Precision and Bias514.1 PrecisionTests b

39、y two laboratories on two samplesgave results equivalent to the nitrometer in precision and bias.No more extensive interlaboratory testing has been undertakenas yet.14.2 BiasNo statement on bias can be made as no suitablereference material is available as a standard.15. Keywords15.1 nitrogen content

40、; soluble nitrocelluloseASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringe

41、ment of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard o

42、r for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views k

43、nown to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting A

44、STM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).5Supporting data have been filed at ASTM Int

45、ernational Headquarters and maybe obtained by requesting Research Report: RR:D01-1056.TABLE 1 Suggested Settings for Brinkman 20EP-1 SelectEP-1Setting,mVProposedBandAMinimumDeliveryAStandardizations withKNO3-mV EP-1 350 80 100Analysis of nitro-cellulose-mV EP-1 200 80 100AThese are approximations only. Settings can vary between instruments.D4795 94 (2008)3