1、Designation: D1681 05 (Reapproved 2014)Standard Test Method forSynthetic Anionic Active Ingredient in Detergents byCationic Titration Procedure1This standard is issued under the fixed designation D1681; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of revision, the year of last 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 Direct titration of an anionic surfactant with a standard-ized cationic reagent is a s
3、imple and convenient method for thequantitative determination of the content of active ingredient.The end point is detffected by the transfer of a colored complexfrom an organic solvent phase to an aqueous phase. Therelationship between anionic and cationic agents is not alwaysstoichiometric, and fo
4、r maximum accuracy the anionic type ofinterest should first be characterized and then used to standard-ize the cationic reagent. In most cases, however, the differentanionic surfactants likely to be encountered react in the sameproportions. That is, a cationic titrating solution standardizedagainst
5、a characterized anionic agent can be used to analyzeother anionics of known molecular weights.1.2 This test method is applicable to alkylaryl sulfonatesand fatty alkyl sulfates. Low results are obtained with alkyl-benzene sulfonates having the alkyl chain length less than eightcarbon atoms. Low resu
6、lts are also obtained for alkyl sulfateswith the alkyl chain length of less than twelve carbon atoms.The anionic surfactants characterized in accordance withSections 1723should be the sodium salt and not amine,ammonium, or potassium salts. In case only amine or ammo-nium salts are available, they sh
7、ould be first converted to thesodium salt before proceeding with this analysis.1.3 The analytical procedures appear in the following order:SectionsSeparation of Alcohol-Soluble Matter 8 and 9Separation of Oil-Free Sulfonate 10 and 11Determination of Sodium Chloride (NaCl) Content 1217Characterizatio
8、n of Anionic Surfactant Standard:Part I. Determination of Surfactant, SO3Content, and SolutionMolarity1820Part II. Determination of Surfactant, SO3and Active IngredientContents Combining Weight, and Solution Molarity2124Standardization of Cationic Reagent 2529Quantitative Determination of Anionic Su
9、rfactant by CationicTitration30331.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user o
10、f this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For a specifichazards statement, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water3. Summary of Test Method3.1 T
11、his test method involves isolating alkylaryl sulfonateor fatty alkyl sulfate by extraction with ethyl alcohol to removeinorganic salts, extracting the alcohol-soluble material withpetroleum ether to remove unsulfonatable matter, correctingfor sodium chloride present, and determining the active ingre
12、-dient combining weight. The characterized surfactant is used tostandardize a cationic reagent which in turn is used to titratesimilar anionic surfactants.4. Significance and Use4.1 This test method determines anionic detergents com-monly found in laundry, dishwashing, and other cleaningmaterials. A
13、ccurate determination of the anionic active sub-stance is highly important in assessing the cost and effective-ness of such cleaning substances.5. Interferences5.1 With the exception of picrate, perchlorate, thiocyanate,nitrate, dichromate, and chromate, common inorganic anionsand low molecular weig
14、ht organic anions do not interfere withthis analysis. However, sulfonates of xylene, cunene, or tolu-ene interfere positively. Since the cationic titration is con-ducted under acidic conditions, soap does not interfere. Soap1This test method is under the jurisdiction of ASTM Committee D12 on Soapsan
15、d Other Detergentsand is the direct responsibility of Subcommittee D12.12 onAnalysis and Specifications of Soaps, Synthetics, Detergents and their Components.Current edition approved Jan. 1, 2014. Published February 2014. Originallyapproved in 1959. Last previous edition approved in 2005 as D1681 05
16、. DOI:10.1520/D1681-05R14.2For 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 page onthe ASTM website.Copyright ASTM International, 100 B
17、arr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1must not be present in the anionic surfactant characterized inaccordance with Sections 1723.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended th
18、atall 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 the reagent is ofsufficiently high purity to permit its use without les
19、sening theaccuracy of the determination.6.2 Unless otherwise indicated, references to water shall beunderstood to mean reagent water conforming to SpecificationD1193.37. Hazards7.1 All reagents and chemicals should be handled with care.Before using any chemical, read and follow all safety precau-tio
20、ns and instructions on the manufacturers label or MSDS(Material Safety Data Sheet).SEPARATION OF ALCOHOL-SOLUBLE MATTER8. Solvent8.1 Ethyl AlcoholFreshly boiled ethyl alcohol conformingto Formula No. 3A or No. 30 of the U.S. Bureau of InternalRevenue. The alcohol should not be neutralized. Redistill
21、edalcohol must be used if alkali absorption is more than 0.2 mLof 100 mL of 0.1 N NaOH solution.9. Procedure9.1 Weigh out a sample, to the nearest 0.01 g, to correspondto surfactants with the following ranges of active ingredientcontents and transfer to a 600-mL beaker:Active Ingredient, wt % Weight
22、 of Sample, g10 to 25 3025 to 40 1540 to 60 1060 to 80 7Over 80 5.59.2 Add 300 to 350 mL of hot alcohol. Cover with a watchglass and heat on the steam bath for at least 2 h, stirringfrequently to disperse solids and break up lumps. Have aprepared Gooch crucible or sintered glass filter inserted in t
23、he1000-mL vacuum flask.9.3 At the end of 2 h, remove the beaker from the bath anddecant the alcohol solution rapidly through the filter, retainingas much as possible of the residue in the beaker. Add 50 mL ofhot alcohol to the residue in the beaker. Heat to boiling on a hotplate, breaking up any lum
24、ps of the residue. Decant the alcoholthrough the filter as before. Repeat with another 50-mL portionof hot alcohol.9.4 Evaporate the residual alcohol from the residue in thebeaker on the steam bath, stirring at intervals, especially nearthe end. Dissolve the residue in the beaker with 10 mL of hotwa
25、ter, heating on the steam bath until solution is effected.9.5 Dilute the water solution with 200 mL of hot alcohol,bring to a boil on the steam bath, and filter. Transfer theprecipitate onto the filter with the aid of hot alcohol andpoliceman. Wash the beaker and the residue with hot alcoholthree or
26、 four times. For samples being prepared for Part I of thecharacterization of anionic surfactant (Sections 1820),continue as directed in 9.6. For samples being prepared foreventual use in Part II of the characterization of anionicsurfactant (Sections 2124), continue in accordance with theseparation o
27、f oil-free sulfonate (Sections 10 and 11).9.6 Transfer the filtrate to a 1000-mL beaker. Wash the filterflask with alcohol and 10 mL of water followed by an alcoholwash. Evaporate the filtrate to about 400 mL and transfer to a1000-mL volumetric flask. Dilute with water to mark. Desig-nate as Solutio
28、n I and reserve for use in Part I of thecharacterization of the anionic surfactant (Sections 1820).SEPARATION OF OIL-FREE SULFONATE10. Reagents10.1 Ethyl AlcoholSee Section 8.10.2 Petroleum Ether, having a boiling point of 30 to 60C.11. Procedure11.1 Transfer the alcohol solution quantitatively to a
29、1000-mL beaker (with the 100-mL volume marked on the side)and concentrate to 100 mL on a steam bath or hot water bath.Transfer the concentrate quantitatively to a 500-mL, pear-shaped separatory funnel by rinsing the beaker with 100 mL ofwater in several portions. Add the remainder of water to thefun
30、nel to bring the total volume to 200 mL.11.2 Extract the aqueous-alcoholic solution with three 50-mL portions of petroleum ether, using additional separatoryfunnels. Combine the ether extracts and wash with 3 to 50- mLportions of 50 % aqueous ethanol. Add the aqueous ethanolwashings to the extracted
31、 aqueous alcohol solution. Discard thepetroleum ether extracts. Transfer the oil-free aqueous alco-holic solution quantitatively to a 1000-mL beaker by rinsingthe separatory funnel with small portions of water. Heat thesolution in a 400-mL beaker in a water bath at 40 to 50C in ahood to vent off pet
32、roleum ether fumes. When free of ether,transfer the oil-free salt-free solution quantitatively to a1000-mLvolumetric flask.Add 300 mLof alcohol and dilute tovolume with water. Designate as Solution II and reserve for usein Part II of the characterization of the anionic surfactant(Sections 2124).3Rea
33、gent Chemicals, American Chemical Society Specifications, 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 Pharmacopeiaan
34、d National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D1681 05 (2014)2DETERMINATION OF SODIUM CHLORIDE (NaCl)CONTENT12. Scope12.1 Sections 1317cover the determination of the sodiumchloride content of the surfactant in order that appropriatecorrections can be made in the valu
35、es obtained in the charac-terization of the anionic active ingredients and the quantitativedetermination of an unknown anionic active ingredient.13. Apparatus13.1 Stirrer Motor and Small Glass Rod Stirrer.13.2 Potentiometer.413.3 Calomel Reference Electrode, saturated.13.4 Silver Wire Electrode, 1mm
36、 in diameter by 120 mm inlength.14. Reagents and Materials14.1 Acetone.14.2 Ethyl AlcoholFreshly boiled ethyl alcohol conform-ing to Formula No. 3Aor No. 30 of the U.S. Bureau of InternalRevenue.14.3 Methyl Orange Indicator.14.4 Nitric Acid (1+1)Mix 1 volume of HNO3(sp gr 1.42)containing 0.3 % sodiu
37、m nitrite (NaNO2) with 1 volume ofwater.14.5 Nitric Acid (1+4)Mix 1 volume of nitric acid(HNO3, sp gr 1.42) with 4 volumes of water.14.6 Silver Nitrate, Standard Solution (0.2 N)Prepare andstandardize a 0.2 N silver nitrate (AgNO3) solution as follows:Weigh 17 g of AgNO3to the nearest 1 mg. Dissolve
38、 in waterand transfer to a 500-mL volumetric flask. Dilute to the mark.Standardize as follows:14.6.1 Dry about 10 g of NaCl at 110C to constant weight.Weigh about 2.00 g of the dried NaCl to the nearest 1 mg.Dissolve in a solvent consisting of 60 % water and 40 %alcohol. Transfer to a 100-mL volumet
39、ric flask and dilute to themark with solvent. Pipet 100 mL of the NaCl solution to abeaker and titrate with the AgNO3solution as described inSection 15.14.6.2 Calculate the normality of the AgNO3solution asfollows:Normality 5 A 3100!/B 358.45! (1)where:A = grams of NaCl used, andB = millilitres ofAg
40、NO3solution required for titration of theNaCl.15. Procedure for Qualitative Determination15.1 Place 5 mL of Solution I or II in a test tube and acidifywith HNO3(1+4). Add several drops of AgNO3solution. If thesolution becomes turbid, it contains NaCl. Presence of soapwill also cause turbidity. Soap
41、must not be present with thesurfactant to be characterized.16. Procedure for Quantitative Determination16.1 Pipet 100-mL portions of Solution I or II into each oftwo 400-mL beakers. Add 2 drops of methyl orange indicatorsolution and acidify to the acid color by using HNO3(1+4).Warm slightly and stir
42、 to effect maximum solution. Add 50 mLof acetone.16.2 Clean the silver electrode in the HNO3(1+1) contain-ing NaNO2. Set up the titration cell with the silver electrodeconnected to the top terminal, the saturated calomel cellconnected to the bottom terminal. Set the pH meter on + mV.Start the stirri
43、ng and titrate the solution potentiometrically asfollows:16.2.1 Add 0.5 mL ofAgNO3solution and measure the emf.If appreciable chloride is present, the emf should be in therange of 100 mV.16.2.2 Add AgNO3solution slowly in 2 to 3-mL portionsuntil the emf reaches 200 mV. Stir well.16.2.3 Add AgNO3solu
44、tion in 0.1-mL portions, allowingsufficient time after each addition for the solution to reachequilibrium (60 to 80 s). Measure the emf (stirrer off) at each0.1-mL point.16.2.4 Calculate the end point by the rate of change method(Note 1). The end point is usually in the range from 260 to 270mV.NOTE
45、1ExampleThe method for determining the maximum rate ofchange is as follows:mL emf E E21.2 210 10 1021.3 220 20 17A21.4 240 37 1221.5 277 2521.6 302AMaximum rate of change.End point 5 21.31171711230.1 (2)521.46 mL16.3 Run a blank and subtract the value obtained from thevalue calculated in 16.2.4.17.
46、Calculations17.1 Calculate the grams of NaCl present in 250 mL ofSolution I or II as follows:A 5 B 3 N 30.05845 3250!/100 (3)where:A = grams of NaCl present in 250 mL of Solution I or II,B = millilitres of AgNO3solution required for titration ofthe NaCl, andN = normality of the AgNO3solution.17.2 Ca
47、lculate the grams of NaCl equivalent to sodiumsulfate (Na2SO4) present in 250 mL of Solution I or II asfollows:4The Beckman Model G pH meter, or its equivalent, has been found satisfactoryfor this purpose.D1681 05 (2014)3A 5 B 371.03!/58.45 (4)where:A = grams of Na2SO4equivalent to the NaCl in 250 m
48、L ofSolution I or II, andB = grams of NaCl present in 250 mL of Solution I or II.CHARACTERIZATION OF ANIONICSURFACTANT STANDARDPart I. Determination of Surfactant, SO3Content, and Solution Molarity18. Reagents18.1 Ethyl AlcoholSee Section 6.18.2 Sulfuric Acid (sp gr 1.84)Concentrated sulfuric acid(H
49、2SO4).19. Procedure19.1 Pipet 250 mL of Solution I (9.6) into each of two250-mL beakers. Evaporate to near dryness on a steam bath orunder an infrared lamp. Transfer quantitatively the concen-trated solution from the beaker into a tared, ignited, platinumcrucible. Wash the beaker with small amounts of alcohol andwater to ensure complete transfer to the crucible.19.2 Evaporate the contents in the crucible to dryness on asteam bath or under an infrared lamp, adding small portions ofalcohol to aid in removal of water.19.3 Carefully heat the cr
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