1、Designation: D1696 95 (Reapproved 2011)Standard Test Method forSolubility of Cellulose in Sodium Hydroxide1This standard is issued under the fixed designation D1696; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、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 This test method2is intended for application todissolving-type cellulose pulps prepared from cotton or wood.The procedure i
3、s 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.1.3
4、 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. Refer
5、enced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterD1347 Test Methods for Methylcellulose4D1348 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 aspec
6、ified 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 21.5 %are
7、 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-,” “beta-,” o
8、r “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. Alternativ
9、e 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 is ins
10、oluble 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-Temperature Ba
11、thA 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 CrucibleA fritted-glass filter cru-cible,
12、 coarse porosity (pore size 40 to 60 m), of 30-mLcapacity.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 Cellulose Derivatives.Current edition approved
13、 June 1, 2011. Published June 2011. Originallyapproved in 1959. Last previous edition approved in 2006 as D1696 95 (2006).DOI: 10.1520/D1696-95R11.2This test method is an adaptation of the method designated CCA 8:55 by theAnalysis Committee of the Central Committee of the Cellulose Industry of theSw
14、edish Association of Pulp and Paper Engineers. This test method is alsocomparable with the 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 Ann
15、ual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.5Available from Technical Association of the Pulp and Paper Industry (TAPPI),P.O. Box 105113,At
16、lanta, GA30348; 15 Technology Parkway South, Norcross, GA30092.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4 Electrometric Titration ApparatusFor estimation ofdichromate by titration with ferrous ammonium sulfate. Anindicator m
17、ay be used as described in 8.6, but for rapid,accurate analysis an electrometric apparatus is recommended.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 An
18、alyticalReagents of the American Chemical Society,6where suchspecifications are available. Other grades 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, r
19、eferences to water shall beunderstood to mean reagent water conforming to SpecificationD1193.7. Reagents7.1 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
20、Sulfate Solution (0.1 N)Dissolve40 to 41 g of ferrous ammonium sulfate (FeSO4(NH4)2-SO46H2O) in water 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 pot
21、assium dichromate (K2Cr2O7), transfer to a 2-L beaker,and dissolve in approximately 700 mL of water. Add, withconstant stirring, 150 mL of H2SO4. Allow to cool to roomtemperature. Dilute to 1 L with water.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washing
22、ton, 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, Inc. (USPC), Rockville,MD.Metric Equiv
23、alentsin.mm183.2146.41212.73419.0125.431482.6612165.1858219.1FIG. 1 Design Details of Mechanical StirrerD1696 95 (2011)27.4 Potassium Iodide (KI).77.5 Sodium Hydroxide SolutionDissolve solid sodiumhydroxide (NaOH) in an equal weight of water. Cover andallow to stand about one week to permit settling
24、 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 volume of 50 % NaOH solution fromthe stock bottle; do not disturb the Na2CO3precipitate. The
25、Na2CO3content 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 0.1 g NaOH per 100 g of solution.Specific gravity at 20/4C is 1.1089. This solution is 2.77
26、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 %)Prepare a so-lution containing 21.5 6 0.1 g NaOH per 100 g of solution.Specific gravity
27、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 D1347.7.7 Starch Solution (5 g/L).7.8 Sulfuric Acid (sp gr 184)Concentrated sulfuric acid(H2SO4).8. Preparation o
28、f 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 solubility analysis.8.2 If the pulp is in sheeted form, tear it into pieces about 10mm square. Do not
29、 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 the air-dry sample inaccordance with Test Methods D1348. Calculate the oven-dryweight of the
30、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, temperatures of 20 6 2C aresatisfactory in this case. However, pulp solubility in 10 %NaOH soluti
31、on 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 NaOHsolution of the desired concentration (10, 18, or 21.5 %) into a250-mL beaker. Add the 1.6 g
32、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 the pulpby stirring for 3 min (Note 1). Adjust the stirring speed toprevent addition of air to
33、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 glass and leave inthe 20C bath until a total of 60 min have elapsed from the timeof addition
34、 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 21.5 % NaOH, thesample container may be removed from the bath for thedisintegration process.NO
35、TE 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 thedisintegration is not complete. The stirrer should, therefore, be run untilcomplete disintegration is o
36、btained, 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 suction but do not pull airthrough the cellulose mat on the filter. Discard the first 10 mLof
37、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 filtrates to250-mL Erlenmeyer flasks. Add 10 mL K2Cr2O7solution toeach flask; then carefully a
38、dd 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 maintain a temperaturein the range of 125 to 130C for the entire 10-min period. A reflux syste
39、mis 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 offiltrate to 5 mL and the volume of H2SO4to 25 mL. For pulpswith alkali solubility less than
40、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 ammonium sulfatesolution. An electrometric titrimeter is preferred for thisoperation. If this equipm
41、ent 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 solution with about 500 mL of water to a1-L Erlenmeyer flask. Add about 2 g of Kl and after 5
42、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.7This reagent is required only for the iodometric method for measuringdichromate (see section 9.7). Thyodene, supplied
43、 by Fisher Scientific Co., Pitts-burgh, PA is an acceptable substitute.D1696 95 (2011)310. Calculations10.1 Calculate 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 forti
44、tration of the sample, mL,b = ferrous ammonium sulfate solution required fortitration of the blank, 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
45、 of sample used, g.NOTE 3The factor 68.5 is the experimental value recommended inmethod CCA 8:55.2As 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: Disso
46、lve 200 mg (oven-dry weight) of high-quality cotton linterspulp in H2SO4(3 + 1) (prepared by mixing 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 o
47、f this solution in the proceduredescribed in Section 8 for blank and sample treatment. Compare 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 solubilit
48、y, % 5 10 Cb 2 a!#/mw (2)where:C = concentration of ferrous ammonium sulfate solution in terms 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 68.5m
49、w (3)where:V1=Na2S2O3solution required for titration of the sample,mL,V2=Na2S2O3solution required 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
