1、Designation: D1166 84 (Reapproved 2013)Standard Test Method forMethoxyl Groups in Wood and Related Materials1This standard is issued under the fixed designation D1166; 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 () 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 (1-7).2The test method isapplic
3、able to wood sawdust and, by suitable adjustment in sizeof 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 appro-pr
4、iate 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 the meth
5、yl iodide iscollected in an acetic acid solution of potassium acetatecontaining bromine. The following reactions then occur:CH3I1Br2CH3Br1IBr (1)IBr12Br213H2OHIO315HBrThe iodic acid is determined by titration of iodine liberatedby the reaction:HIO315HI3I213H2O (2)From the above equations, it follows
6、 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 and shall consist
7、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 ReagentsReagent grade chemi
8、cals 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 American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained
9、 that the 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 th
10、e absence 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 thel
11、iquid level, 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 gasphosphine, PH3, may be formed under certain conditions, andthis may unite with molec
12、ular iodine 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 sa
13、fety precaution, the distillation should be1This 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 Aug. 1, 2013. Published August 2013. Originallyapproved in 19
14、56. Last previous edition approved in 2007 as D1166 84 (2007).DOI: 10.1520/D1166-84R13.2The boldface numbers in parentheses refer to the references listed at the end ofthis test method.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For sugges
15、tions 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.Copyright ASTM International,
16、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1conducted 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 H3
17、PO2(50 %) necessary toeffect complete de-colorization.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)Dissolv
18、e 78.5 g of Na2S2O35H2O in water and dilute to 1L(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 N
19、aHCO3solution and the second containing H2SO4(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 signif
20、icant.6.7 Liquid Bromine.6.8 Sodium Acetate Solution (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 c
21、olor due tofree iodine. If a blank titration on 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
22、anddilute to 1 L. Use freshly boiled and cooled 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 the
23、National Bureau of Standards (standard sample No. 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
24、N KMnO4, while swirling the flask gently. Tothe 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 thetit
25、ration until the blue color has just been destroyed. 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 s
26、oluble starch in 5 mL of water and add to 100 mL 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
27、 preparations of high methoxyl content, it isrecommended 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 betransfer
28、red with the specimen to the reaction flask. The 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-stopperedFIG. 1 Apparatus for Methoxy
29、l DeterminationD1166 84 (2013)2weighing bottle. Dry in an oven for 12 h at 100 to 105C,replace the stopper, 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.9
30、. Procedure9.1 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
31、 should 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
32、 vertical 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 th
33、en bethoroughly 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 oth
34、er interfering 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 tria
35、l determination, 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 m
36、anner and their average issubtracted from the titration of the sample.9.3 Let the reaction flask cool below 100C. In themeantime, add to 20 mL of the potassium acetate solution,about 0.6 mL of bromine, and mix. Add approximately 15 mLof the mixture to the first receiver and 5 mL to the second, andat
37、tach the receiver to the apparatus. Seal the ground-glass jointwith a 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 theconten
38、ts 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.Usuall
39、y, 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
40、more 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
41、 of 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 331.03! 3100!/G 31000 36! (3)5VN/G! 30.517where:V = millilitres of Na2S2O3solution required for thetitration,N = normality of Na2S2O3so
42、lution, 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.,“ Quan
43、titative 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 Gos
44、sypol 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, p.
45、 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. 181.
46、(7) Samsel, E. P., and McHard, J. A., “Determination of Alkoxyl Groupsin Cellulose Ethers,” Industrial and Engineering Chemistry, Analyti-cal Edition, Vol 14, 1942, p. 750.D1166 84 (2013)3ASTM International takes no position respecting the validity of any patent rights asserted in connection with an
47、y 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 technical
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