1、Designation: D 1166 84 (Reapproved 2007)Standard Test Method forMethoxyl Groups in Wood and Related Materials1This standard is issued under the fixed designation D 1166; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 method covers the determination of methoxylgroups in wood and related materials (1 to 7).2The test methodis
3、applicable to wood sawdust and, by suitable adjustment insize of the test specimen, to fractions isolated from wood andlignin.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 ap
4、pro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 6.2. Principle of Method2.1 The principle of the test method is the same as that in theoriginal method of Zeisel (1), except that th
5、e methyl iodide iscollected in an acetic acid solution of potassium acetatecontaining bromine. The following reactions then occur:CH3I 1 Br2CH3Br 1 IBrIBr 1 2Br21 3H2OHIO31 5HBr (1)The iodic acid is determined by titration of iodine liberatedby the reaction:HIO31 5HI3I21 3H2O (2)From the above equat
6、ions, it follows that one methoxylgroup (CH3O) liberates six atoms of iodine.3. Significance and Use3.1 Most of the methoxyl in wood is attributable to thelignin. This test method is used extensively in the study oflignin.4. Apparatus4.1 The apparatus shall be similar to that illustrated in Fig.1 an
7、d shall consist of the following:4.1.1 Reaction Flask,4.1.2 Heat SourceA microburner, provided with a cylin-drical shield to eliminate the effect of air drafts,4.1.3 Vertical Air-Cooled Condenser,4.1.4 Scrubber, and4.1.5 Two Absorption Vessels.5. Purity of Reagents and Water5.1 Purity of ReagentsRea
8、gent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended that1This test method is under the jurisdiction of ASTM Committee D07 on Woodand is the direct responsibility of Subcommittee D07.01 on Fundamental TestMethods and Properties.Current edition approved April 1,
9、2007. Published April 2007. Originallyapproved in 1956. Last previous edition approved in 2001 as D 1166 84 (2001).2The boldface numbers in parentheses refer to the references listed at the end ofthis test method.FIG. 1 Apparatus for Methoxyl Determination1Copyright ASTM International, 100 Barr Harb
10、or Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that th
11、e reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.5.2 WaterUnless otherwise indicated, references to watershall be understood to mean distilled water.6. Reagents6.1 Hydriodic Acid (sp gr 1.70)The best reagent grade HI,if stored in the absenc
12、e of light and at a low temperature, maybe used without redistillation. If purification is necessary, theHI may be redistilled. If purification is necessary, the HI maybe redistilled after addition of a few grams of red phosphorus,taking care not to overheat the sides of the flask above theliquid le
13、vel, and collecting the distillate which comes overbetween 124 and 130C. A slow stream of CO2should bemaintained through the receiver during the distillation.(WarningDuring the distillation, the poisonous gas phos-phine, PH3, may be formed under certain conditions, and thismay unite with molecular i
14、odine to form the explosive PI3,similar in properties to NI3. The PI3may explode on contactwith air. It is therefore advisable to keep the current of CO2going after the distillation has been finished, until the apparatushas cooled; this prevents air from being sucked into theapparatus. As a safety p
15、recaution, the distillation should beconducted in a hood or behind a wire-glass shield.) A perma-nently colorless solution of hydriodic acid may be obtained ifthe liquid, heated to approximately 100C, is treated withslightly more than the quantity of H3PO2(50 %) necessary toeffect complete de-colori
16、zation.6.2 Phenol.6.3 Cadmium Sulfate Solution (50 g CdSO4/L)Dissolve67.2 g of CdSO44H2O in water and dilute to 1 L.NOTE 1A water suspension of red phosphorus is equally satisfactoryin the scrubber.6.4 Sodium Thiosulfate Solution (50 g Na2S2O3/L)Dissolve 78.5 g of Na2S2O35H2O in water and dilute to
17、1 L(Note 1).6.5 Carbon Dioxide GasThe CO2may be drawn from acylinder of the compressed gas. It may be obtained also by theuse of a Kipp generator and washed, before introduction intothe apparatus, through two wash bottles, the first containingsaturated NaHCO3solution and the second containing H2SO4(
18、sp gr 1.84). Solid CO2, or “dry ice,” is a convenient source (5)and the gas requires no purification.6.6 Potassium Acetate Solution in Acetic AcidDissolve100 g of anhydrous potassium acetate in 1 L of glacial aceticacid. Traces of moisture are not significant.6.7 Liquid Bromine.6.8 Sodium Acetate So
19、lution (250 g/L)Dissolve 415 g ofsodium acetate trihydrate in water and dilute to 1 L.6.9 Formic Acid (90 %).6.10 Potassium Iodide Solution (100 g KI/L)Dissolve 100g of KI in water and dilute to 1 L.NOTE 2The KI solution, on standing, develops a yellow color due tofree iodine. If a blank titration o
20、n the solution consumes Na2S2O3, a freshsolution should be prepared.6.11 Sulfuric Acid (1 + 9)Mix one volume of H2SO4(spgr 1.84) with nine volumes of water.6.12 Standard Sodium Thiosulfate Solution (0.1 N)Dissolve 25 g of Na2S2O35H2O in 200 mL of water anddilute to 1 L. Use freshly boiled and cooled
21、 water. It ispreferable to allow the solution to stand for a few days beforestandardization. Standardize the solution against an approxi-mately 0.1 N solution of KMnO4that has been standardizedagainst sodium oxalate oxidimetric standard furnished by theNational Bureau of Standards (standard sample N
22、o. 40). Ineach of two glass-stoppered Erlenmeyer flasks put2gofKIand 100 mL of freshly boiled and cooled water. Shake todissolve the KI and add 2 mL of HCl (sp gr 1.18). To one flaskadd slowly from a buret either 20.0 mL of 0.1 N KMnO4or10.0 mL of 0.18 N KMnO4, while swirling the flask gently. Tothe
23、 other flask add an equal volume of water. Stopper the flasksand let them stand in the dark for 10 min. Titrate the iodine thathas been set free with the Na2S2O3until the solution is of afaint straw color. Add 2 mL of starch solution and continue thetitration until the blue color has just been destr
24、oyed. Subtractthe volume of Na2S2O3required in the blank determinationfrom that required in the other titration, and calculate thenormality of the Na2S2O3, based on the normality of theKMnO4.6.13 Starch Indicator Solution (10 g/L)Make a paste of 1g of soluble starch in 5 mL of water and add to 100 m
25、L ofboiling water. Prepare fresh as needed.7. Test Specimen7.1 The test specimen of wood shall consist of about 0.1 g,weighed to the nearest 0.0001 g, of air-dry sawdust that hasbeen ground to pass a 420-m sieve. For analysis of isolatedlignins or other preparations of high methoxyl content, it isre
26、commended that the specimen not exceed 0.05 g. Forspecimens of very low methoxyl content, the specimen may beincreased to 0.2 g.7.2 The specimen may be weighed in a glass boat, in agelatin capsule, or on a cigarette paper. The container shall betransferred with the specimen to the reaction flask. Th
27、e paperor capsule shall contain no methoxyl groups, as determined bya separate analysis.8. Moisture Determination8.1 At the same time the test specimen is weighed, weigh0.1 g of the air-dry sawdust in a tared, glass-stopperedweighing bottle. Dry in an oven for 12 h at 100 to 105C,replace the stopper
28、, and cool in a desiccator. Loosen thestopper to equalize the pressure and weigh. Continue thedrying for 1-h periods until the weight is constant. Calculatethe percentage of moisture-free wood.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. Fo
29、r 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. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.D 1166 84 (2007)29. Pr
30、ocedure9.1 Place in the reaction flask 15 mL of HI,7gofphenol,and a 10-mm length of Nichrome wire or a boiling tube (Note3) to prevent bumping. Place in the scrubber a mixture of equalvolumes of CdSO4solution (50 g CdSO4/L) and Na2S2O3solution (50 g Na2S2O3/L) (see Note 1). The volume ofsolution sho
31、uld be adjusted so that the inlet tube of the scrubberis covered to a depth of about 4 mm. Adjust the flow of CO2toabout 60 bubbles per minute through the scrubber (Note 4).NOTE 3A boiling tube may be prepared by sealing off a piece ofthin-wall capillary tubing of such length that it will remain ver
32、tical in thereaction flask, and inserting it with the open end down. If the CO2introduction tube extends to the bottom of the flask, no anti-bumpingdevice is necessary.NOTE 4Two to four samples may be analyzed with one charge ofreagents in the reaction flask and scrubber. The apparatus should then b
33、ethoroughly cleaned.9.2 Bring the contents of the flask to reaction temperature.Adjust the rate of heating so that the vapors of the boiling HIrise about 100 mm into the condensor. Heat the flask at reactiontemperature for 30 to 45 min, or longer if necessary, to removemethoxyl-containing or other i
34、nterfering substances which areusually present in the reagents.NOTE 5An appreciable blank may rise from the reagents used. Thegreater part of this blank is removed by a preliminary “burning out”period. In normal work, the time required to remove interfering substancesmust be determined by a trial de
35、termination, in the absence of a testspecimen, for a particular lot of reagents. For the highest accuracy, it isrecommended that the residual blank be ascertained by “blank” determi-nation before and after the determination on the test specimen. Theseblank determinations are made in the normal manne
36、r and their average issubtracted from the titration of the sample.9.3 Let the reaction flask cool below 100C. In the mean-time, add to 20 mL of the potassium acetate solution, about 0.6mL of bromine, and mix. Add approximately 15 mL of themixture to the first receiver and 5 mL to the second, and att
37、achthe receiver to the apparatus. Seal the ground-glass joint witha small drop of water from the glass rod.9.4 Remove the distilling flask and introduce the test speci-men. Immediately reconnect the flask and seal the ground-glassjoint with a drop of molten phenol from a glass rod. Bring thecontents
38、 of the flask to reaction temperature while passing auniform stream of CO2through the apparatus. Adjust the rateof heating so that the vapors of the boiling HI rise about 100mm into the condenser. Continue the heating for a timesufficient to complete the reaction and sweep out the apparatus.Usually,
39、 not more than 50 min are required.9.5 Wash the contents of both recievers into a 250-mLErlenmeyer flask that contains 15 mL of sodium acetatesolution. Dilute with water to approximately 125 mL and add6 drops of formic acid. Rotate the flsk until the color of thebromine is discharged, then add 12 mo
40、re drops of formic acidand allow the solution to stand for 1 to 2 min. Add 10 mL ofKI solution and 10 mL H2SO4(1 + 9), and titrate the liberatediodine with Na2S2O3solution, adding 1 mL of starch indicatorsolution just before the end point is reached and continuing thetitration to the disappearance o
41、f the blue color.10. Calculation and Report10.1 Calculate the percentage of methoxyl groups, based onthe weight of moisture-free wood, as follows:Methoxyl, % 5 VN 3 31.03! 3 100!/G 3 1000 3 6!5 VN/G! 3 0.517 (3)where:V = millilitres of Na2S2O3solution required for thetitration,N = normality of Na2S2
42、O3solution, andG = grams of moisture-free wood in the test specimen.10.2 Report the results to the second decimal place.11. Precision and Bias11.1 Sufficient data is not currently available to develop aprecision and bias statement.12. Keywords12.1 lignin; methoxyl; sawdustREFERENCES(1) Zeisel, S.,“
43、Quantitative Estimation of Methoxyl,” Monatshefte frchemie, Vol 6, 1885, p. 989; Vol 7, 1886, p. 406.(2) Friedrich, A., “Micromethoxyl Determination,” Zeitschrift fr Physi-ologische Chemie, Vol 163, 1927, p. 148.(3) Clark, E. P., “The Action of Boiling Hydriodic Acid as Used in theZeisel Method upon
44、 Gossypol and Some of Its Derivatives. ASemimicro Zeisel Methoxyl Method,” Journal, Am. Chemical Soc.,Vol 51, 1929, p. 1479.(4) Viebck, F., and Schwappach, A., “New Method for the VolumetricDetermination of the Methoxyl and Ethoxyl Groups,” Berichte derDeutschen Chemischen Gesellschaft, Vol 63, 1930
45、, p. 2818.(5) Peniston, Q. P., and Hibbert, H., “The Determination of MethoxylGroups in Pulp and Plant Materials,” Paper Trade Journal, Vol 109,No. 17, Oct. 26, 1939, p. 46.(6) Bailey, A. J., “An Improved Methoxyl Apparatus,” Industrial andEngineering Chemistry, Analytical Edition, Vol 14, 1942, p.
46、181.(7) Samsel, E. P., and McHard, J. A., “Determination of Alkoxyl Groupsin Cellulose Ethers,” Industrial and Engineering Chemistry,AnalyticalEdition, Vol 14, 1942, p. 750.D 1166 84 (2007)3ASTM International takes no position respecting the validity of any patent rights asserted in connection with
47、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 responsible technic
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49、 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, 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 ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm
