1、Designation: D 1696 95 (Reapproved 2006)Standard Test Method forSolubility of Cellulose in Sodium Hydroxide1This standard is issued under the fixed designation D 1696; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t 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 This test method2is intended for application todissolving-type cellulose pulps prepared from cotton or wood.The procedur
3、e is not directly applicable to unrefined pulps foruse in chemical conversion processes because solubility equi-librium may not be attained within the specified extractiontime.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.
4、1.3 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 consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Re
5、ferenced Documents2.1 ASTM Standards:3D 1193 Specification for Reagent WaterD 1347 Test Methods for Methylcellulose4D 1348 Test Methods for Moisture in Cellulose2.2 TAPPI Standard:T 429 Method for Alpha-Cellulose in Paper53. Summary of Test Method3.1 Pulp is steeped in a sodium hydroxide solution of
6、 aspecified concentration for1hat20C. The soluble fraction isestimated by dichromate oxidation of the filtered steepingalkali. The concentration of sodium hydroxide used in the pulpextraction process must be reported as part of the analyticalresult. Sodium hydroxide concentrations of 10, 18, and 21.
7、5 %are most frequently used. Data are reported as percent of drysample weight.3.2 The extraction procedure avoids dilution sequences, andtherefore, the results are not comparable to data obtained by thealpha, beta, gamma methods of pulp fractionation (see TAPPIMethod T 429). The terms “alpha-,” “bet
8、a-,” or “gamma-”cellulose must not be applied to any test values obtained by thisprocedure since they are defined only by the method of theirdetermination.3.3 The essential feature of the method is to prepare sodiumhydroxide extracts and oxidize the soluble material withdichromate as described. Alte
9、rnative methods of estimatingdichromate by titration with ferrous ammonium sulfate andsodium thiosulfate are described.4. Significance and Use4.1 The measurement of soluble oxidizable components ofcellulose in sodium hydroxide is indicative of the purity of thecellulose sample, since pure cellulose
10、is insoluble in sodiumhydroxide. The extracted components are typically hemicellu-loses, which are naturally present in the wood. Differences inpulp purity can have a dramatic impact on the processing andproperties of the cellulose derivatives produced from the pulp.5. Apparatus5.1 Constant-Temperat
11、ure BathA water bath maintainedat 20 6 0.2C.5.2 StirrerMechanical stirrer as shown in Fig. 1. All partsin contact with solutions must be of stainless steel. The stirrermotor shall be a variable speed laboratory motor with 1500rpm max speed.5.3 Fritted-Glass Filter Crucible A fritted-glass filtercruc
12、ible, coarse porosity (pore size 40 to 60 m), of 30-mLcapacity.5.4 Electrometric Titration Apparatus For estimation ofdichromate by titration with ferrous ammonium sulfate. Anindicator may be used as described in 8.6, but for rapid,accurate analysis an electrometric apparatus is recommended.1This te
13、st 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 Cellulose Derivatives.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 1959.
14、Last previous edition approved in 2000 as D 1696 95 (2000).2This test method is an adaptation of the method designated CCA 8:55 by theAnalysis Committee of the Central Committee of the Cellulose Industry of theSwedish Association of Pulp and Paper Engineers. This test method is alsocomparable with t
15、he TAPPI Tentative Standard T 235 m-58, Solubility of Pulp inCold Sodium Hydroxide.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary pa
16、ge onthe ASTM website.4Withdrawn.5Available from Technical Association of the Pulp and Paper Industry (TAPPI),P.O. Box 105113,Atlanta, GA30348; 15 Technology Parkway South, Norcross, GA30092.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United S
17、tates.6. Purity of Reagents6.1 Reagent grade chemicals shall be used in all tests.Unless otherwise indicated, it is intended that all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society,6where suchspecifications are available. Other gra
18、des may be used, pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.6.2 Unless otherwise indicated, references to water shall beunderstood to mean reagent water conforming to SpecificationD 1193.7. Rea
19、gents7.1 Ferroin (0.025 M)Dissolve 1.48 g of orthophenan-throline monohydrate (or 1.624 g of the hydrochloride) with0.695 g of ferrous sulfate (FeSO4) in water and dilute to 100mL.7.2 Ferrous Ammonium Sulfate Solution (0.1 N)Dissolve40 to 41 g of ferrous ammonium sulfate (FeSO4(NH4)2-SO46H2O) in wat
20、er containing 10 mL of H2SO4and dilute to 1litre in a volumetric flask. Standardize the solution dailyagainst potassium permanganate (KMnO4).7.3 Potassium Dichromate Solution (20 g/L)Weigh 20.0 gof potassium dichromate (K2Cr2O7), transfer to a 2-L beaker,and dissolve in approximately 700 mL of water
21、. Add, withconstant stirring, 150 mL of H2SO4. Allow to cool to roomtemperature. Dilute to 1 L with water.7.4 Potassium Iodide (KI).76Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the Ame
22、rican 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.7This reagent is required only for the iodometric method for measuringdichromate (se
23、e section 9.7). Thyodene, supplied by Fisher Scientific Co., Pitts-burgh, PA is an acceptable substitute.Metric Equivalentsin.mm183.2146.41212.73419.0125.431482.6612165.1858219.1FIG. 1 Design Details of Mechanical StirrerD 1696 95 (2006)27.5 Sodium Hydroxide SolutionDissolve solid sodiumhydroxide (N
24、aOH) in an equal weight of water. Cover andallow to stand about one week to permit settling of sodiumcarbonate (Na2CO3). Prepare the dilute NaOH solutions listedbelow by approximate addition of freshly boiled water toportions of the concentrated stock solution. Use a siphon towithdraw the required v
25、olume of 50 % NaOH solution fromthe stock bottle; do not disturb the Na2CO3precipitate. TheNa2CO3content of the dilute solutions should not exceed 1g/L. Standardize the final dilute solutions by titration withstandard acid.7.5.1 Sodium Hydroxide Solution (10 %)Prepare a solu-tion containing 10.0 6 0
26、.1 g NaOH per 100 g of solution.Specific gravity at 20/4C is 1.1089. This solution is 2.77 N.7.5.2 Sodium Hydroxide Solution (18 %)Prepare a solu-tion containing 18.0 6 0.1 g NaOH per 100 g of solution.Specific gravity at 20/4C is 1.1972. This solution is 5.39 N.7.5.3 Sodium Hydroxide Solution (21.5
27、 %)Prepare a so-lution containing 21.5 6 0.1 g NaOH per 100 g of solution.Specific gravity at 20/4C is 1.2356. This solution is 6.64 N.7.6 Sodium Thiosulfate Solution (0.1 N)6Prepare andstandardize 0.1 N sodium thiosulfate (Na2S2O3) solution asdirected in 23.11 of Test Methods D 1347.7.7 Starch Solu
28、tion (5 g/L).7.8 Sulfuric Acid (sp gr 184)Concentrated sulfuric acid(H2SO4).8. Preparation of Samples8.1 Condition the air-dry pulp samples to obtain moistureequilibrium by exposing them to the atmosphere for 24 h in theroom where the portions of this sample will be weighed formoisture and solubilit
29、y analysis.8.2 If the pulp is in sheeted form, tear it into pieces about 10mm square. Do not use cut edges. Weigh a portion for moistureanalysis and immediately also weigh, to the nearest 1 mg,about 1.6 g of the air-dry sample for the solubility determina-tion.8.3 Determine the moisture content of t
30、he air-dry sample inaccordance with Test Methods D 1348. Calculate the oven-dryweight of the sample for the solubility determination.9. Procedure9.1 Precool the NaOH solutions to 20C. Pulp solubility in18 and 21.5 % NaOH solutions is not affected by a few degreesvariation in temperature. Hence, temp
31、eratures of 20 6 2C aresatisfactory in this case. However, pulp solubility in 10 %NaOH solution is very sensitive to temperature variation. Theoperator must control temperature to 20 6 0.2C in all phasesof pulp extraction with 10 % NaOH solution.9.2 With a pipet or buret, transfer 100 mL of the NaOH
32、solution of the desired concentration (10, 18, or 21.5 %) into a250-mL beaker. Add the 1.6 g air-dry pulp sample to thesolution. Allow the pulp to swell for 2 min; then introduce thestirring apparatus into the beaker so that the surface of theliquid coincides with the draft tube top. Disintegrate th
33、e pulpby stirring for 3 min (Note 1). Adjust the stirring speed toprevent addition of air to the slurry (about 1500 rpm). Removethe stirrer. Carefully clean the stirring apparatus and walls ofthe beaker with a glass rod so that all pulp fibers are retainedin the alkali. Cover the beaker with a watch
34、 glass and leave inthe 20C bath until a total of 60 min have elapsed from the timeof addition of NaOH to the sample. For solubility determina-tions in 10 % NaOH solution, all extraction operations must beperformed with the sample container in the constant-temperature water bath. In work with 18 or 2
35、1.5 % NaOH, thesample container may be removed from the bath for thedisintegration process.NOTE 1Most pulps are completely disintegrated after 3 min. Areasonable increase in the time of disintegration does not sensibly affectthe solubility. On the other hand, low values are obtained if thedisintegra
36、tion is not complete. The stirrer should, therefore, be run untilcomplete disintegration is obtained, even if the time required exceeds 3min.9.3 At the end of the 1-h total extraction time, remove thebeaker from the bath and immediately filter the slurry througha coarse fritted-glass filter. Apply s
37、uction but do not pull airthrough the cellulose mat on the filter. Discard the first 10 mLof filtrate. If suspended fibers are noted in the filtrate, recyclethe filtrate through the cellulose mat to clarify. Retain thefiltrate in a stoppered Erlenmeyer flask.9.4 Transfer 10-mL aliquots of the NaOH f
38、iltrates to250-mL Erlenmeyer flasks. Add 10 mL K2Cr2O7solution toeach flask; then carefully add 30 mL of H2SO4to each flask.After 10 min (Note 2), cool to room temperature. Include ablank test with the original NaOH extraction solution in thisoperation.NOTE 2It is suggested that heat be applied to m
39、aintain a temperaturein the range of 125 to 130C for the entire 10-min period. A reflux systemis highly satisfactory.9.5 The 10-mL aliquot of the NaOH filtrates specified in 9.4is generally suitable for dissolving-type pulps; however, if thealkali solubility is greater than 16 %, reduce the volume o
40、ffiltrate to 5 mL and the volume of H2SO4to 25 mL. For pulpswith alkali solubility less than 5 %, use 20 mLof filtrate and 45mL of H2SO4.9.6 After dichromate oxidation, add 50 mL of water to eachsample and the blank. Cool again to room temperature. Titratethe excess K2Cr2O7with 0.1 N ferrous ammoniu
41、m sulfatesolution. An electrometric titrimeter is preferred for thisoperation. If this equipment is not available, ferroin indicatormay be used to detect the end point.9.7 An acceptable alternative for measuring dichromateconcentration is to use iodometric methods. In this case,transfer the cooled s
42、olution with about 500 mL of water to a1-L Erlenmeyer flask. Add about 2 g of Kl and after 5 mintitrate the solution to a visual end point with 0.1 N Na2S2O3solution, using starch as the indicator. Make a blank test on theoriginal NaOH extraction solution in the same manner.10. Calculations10.1 Calc
43、ulate the results, when obtained by titration withferrous ammonium sulfate, as follows:Alkali solubility, % 5 b 2 a!N3 68.5/mw (1)where:a = ferrous ammonium sulfate solution required fortitration of the sample, mL,D 1696 95 (2006)3b = ferrous ammonium sulfate solution required fortitration of the bl
44、ank, mL,N = normality of the ferrous ammonium sulfate solu-tion,68.5 = cellulose equivalent to 1 milliequivalent ofK2Cr2O7, times 10 (Note 3), mg,m = filtrate used for oxidation, mL, andw = oven-dry weight of sample used, g.NOTE 3The factor 68.5 is the experimental value recommended inmethod CCA 8:5
45、5.2As an alternative, the problem of standardization offerrous ammonium sulfate can be handled in terms of oxidation of areference cellulose solution prepared at each occasion for analysis asfollows: Dissolve 200 mg (oven-dry weight) of high-quality cotton linterspulp in H2SO4(3 + 1) (prepared by mi
46、xing 3 volumes of H2SO4(sp gr.1.84) with 1 volume of water) and dilute to 100 mL with H2SO4(3 + 1).Do not use heat in the preparation of this solution. Immediately afterpreparation, oxidize 2-mL aliquots of this solution in the proceduredescribed in Section 8 for blank and sample treatment. Compare
47、thecellulose solution and blank to express the concentration of ferrousammonium sulfate solution in terms of milligrams of cellulose permillilitre of solution. The calculation then becomes:Alkali solubility, % 5 10 Cb 2 a!#/mw (2)where:C = concentration of ferrous ammonium sulfate solution in terms
48、ofmilligrams of cellulose per millilitre, andb, a, m, w are defined as in 10.1.10.2 Calculate the results, when obtained by titration withNa2S2O3solution, as follows:Alkali solubility, % 5 V12 V2!N 3 68.5mw (3)where:V1=Na2S2O3solution required for titration of thesample, mL,V2=Na2S2O3solution requir
49、ed for titration of the blank,mL, andN = normality of the Na2S2O3solution, and m and w aredefined as in 10.1.11. Report11.1 Report the alkali solubility as a percentage of oven-drypulp to one decimal place. Use the symbol S for alkalisolubility. Denote the strength of the sodium hydroxide solu-tion by a numerical suffix, for example, designate the solubilityin 10 % NaOH solution by the symbol S10.11.2 If it is of interest to report the insoluble fraction,subtract the S value from 100. Use the symbol R, with theappropriate subscript, to rep
