1、Designation: D 4795 94 (Reapproved 2003)Standard Test Method forNitrogen Content of Soluble NitrocelluloseAlternativeMethod1This standard is issued under the fixed designation D 4795; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 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.1. Scope1.1 Test Methods D 301 for measuring nitrogen content innitrocellulose by nitrometer are the accepted standa
3、rd. How-ever, the glassware is specialized and the precision is depen-dent on the development of a high level of skill by the operator.The ferrous-sulfate titration of nitrate is a classical procedure.By controlling critical variables and automating the actualtitration, precision equivalent to the n
4、itrometer can be achievedwith nitrocellulose. This test method describes such a proce-dure.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, ass
5、ociated 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. For specific hazardstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:D 301 Test
6、Methods for Soluble Cellulose Nitrate2D 1193 Specification for Reagent Water33. 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 factor o
7、f 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 D 301. Under controlled conditions,the procedure described is capable of results equivalent tothose obtained b
8、y 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. However, i
9、f 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 dissol
10、ve 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 Electro
11、de, 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 latch
12、 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 and Cel
13、lulose Derivatives.Current edition approved May 10, 2003. Published June 2003. Originallyapproved in 1988. Last previous edition approved in 1994 as D 4795 94 (1998).2Annual Book of ASTM Standards, Vol 06.03.3Annual Book of ASTM Standards, Vol 11.01.1Copyright ASTM International, 100 Barr Harbor Dri
14、ve, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the America
15、n Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water
16、shall be understood to mean reagent water as definedby Type III of Specification D 1193.7.3 Sulfuric Acid (H2SO4)95to98%.7.4 Ferrous Sulfate SolutionDissolve 350 g of ferroussulfate crystals (FeSO4) in 1000 mL of distilled water. Add1000 mL of 1+1 H2SO4solution. Makes 2 L.7.5 Potassium Nitrate (KNO3
17、) 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 sample of nitrocellulose must be dried, it isimperative that care be exercised in storage, handling, anddisposal. Dry nitrocellu
18、lose is extremely flammable. Refer tothe Procedure section for Drying Samples of Test MethodsD 301.8.2 Strong sulfuric acid used as the solvent for the specimencan burn the skin. The ferrous sulfate titrant is also stronglyacidic. Take proper precautions to protect the operator and theequipment.8.3
19、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 beaker.9. Preparation of Apparatus9.1 If the system has been down for at least 8 h, purge thesystem with 40 mL of ferrous sulfat
20、e 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 a dessicator. If KNO3has been out of the ovenfor4hormore, redry in a 135C oven for a minimum of 2 h.(Nitrocellulose specimens
21、 are dried in a 100C oven for aminimum of 1 h. If out of the oven more than 2 h, redry for12h.) Turn on the pump of the chilled water circulator to startwater flowing through 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 2
22、C).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 to splash ontothe sides of the beaker.10.4 With the stirrer operating and the electrodes up in theair away from the acid, slo
23、wly 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 weight of the standard by difference.10.5 Allow most of the KNO3to dissolve. Visually inspectthe solution until no more chunks o
24、r 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 KNO3dissolves and HNO3is formed by thereaction of H2SO4and the specimen, a millivolt potentialchange is evident by a rising record
25、er 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 are 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 St
26、op 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 titration, immedi-ately record the millilitre reading. Switch the electrode settingto STANDBY.10.12 Raise the electrodes fro
27、m 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.) Discard the tissue into a containerof water. DO NOT allow acid to drip into the circulating-bathwater.10.13 Remove the completed ti
28、tration 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 bleed from the dispenser tip giving areddish tint to the acid.) Replace with clean H2SO4if thisoccurs.NOTE 1It is important to so
29、ak 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 Calculate the nitrogen equivalence factor F for thestandard KNO3as follows:F 5 A 3 13.855!/B (1)where:A = weight of KNO3,g,13.855 = n
30、itrogen equivalence of nitrogen in KNO3or inthe standard material used, andB = 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.4Reagent Chemicals, American Chemical Society Specification
31、s, 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, U.S. Pharmacopeial Convention, In
32、c. (USPC), Rockville,MD.D 4795 94 (2003)211.1.2 For high viscosity types, place the sample into asmall 0.25-L (8-oz) plastic blender jar. Fill to the fill line withtap water, and 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.
33、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 their respectivetimes as follows:Hercules Designation Time, minSS, all 5RS12 4RS14 4RS18 3AS, all 311.2 At the completion of
34、 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 in accordance with the paragraph onsmall quantities in the Procedure section for Drying Samples ofTest Methods D 301.11.4 Af
35、ter 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 oven. Allow time for cooling in adesiccator before weighing. If specimens are out of the ovenfor more than 2 h, redry for12
36、 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 excess H2SO4standard down the sinkand rinse with large quantities of water.13. Calculation13.1 Calculate the percent of nitroge
37、n 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 by two laboratories on two samplesgave results equivalent to the nitrometer in precision and bias.No more extensive interla
38、boratory 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; soluble nitrocelluloseASTM International takes no position respecting the validity of any patent rights asserted in conn
39、ection 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 infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the respons
40、ible 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 or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful c
41、onsideration 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 known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 10
42、0 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 ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM w
43、ebsite(www.astm.org).5Supporting data available from ASTM International Headquarters. Request 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.D 4795 94 (2003)3
