1、Designation: D7638 10 (Reapproved 2015)Standard Test Method forDetermination of Fatty Acids and Esters in Glycerin1This standard is issued under the fixed designation D7638; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、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 This test method provides the quantitative determinationof the fatty acid and ester content in purified glycerin by
3、 thetitrimetric method.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard may involve hazardous materials, opera-tions and equipment. This standard does not purport to addressall of the safety concerns, if any
4、, associated with its use. It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use. Specificprecautions are listed in Section 8.2. Referenced Documents2.1 ASTM Standards:2D1193 Spec
5、ification for Reagent WaterD4725 Terminology for Engine Coolants and Related Fluids2.2 Other Standard:The United States Pharmacopoeia 31 Glycerin Monograph Fatty Acids and Esters33. Terminology3.1 Definitions:3.1.1 glycerinpropane-1,2,3-Triol, C3H5(OH)3(alsoknown as glycerine), 1,2,3-propanetriol, 1
6、,2,3-trihydroxypropane, glyceritol, glycyl alcohol. CAS #56-81-53.1.2 FA thereforeit is advisable to prepare 500 mL of water by boiling for 5 min. Cool toroom temperature. Check the pH of the distilled water before use. The pHshould be 7.0 6 0.1. If not, adjust the pH with 0.1 N sodium hydroxide(NaO
7、H) or 0.1 N hydrogen chloride (HCl), whichever is appropriate.Store the freshly boiled and neutralized water in a tightly closed container.7. Reagents7.1 Phenolphthalein Solution(See Note 2.) Dissolve 1 gof phenolphthalein in 100 mL of ethanol (95 %), methanol orisopropanol. This solution can be pur
8、chased.7.2 Hydrochloric Acid, 0.5 N, aqueous solution(See Note1 and Note 2.) To a 1000-mL volumetric flask containing 40mL of water, slowly add 43 mL of concentrated hydrochloricacid. Cool, and add water to volume. Standardize the solutionto an accuracy of 60.001 N.7.3 Sodium Hydroxide, 0.5 N, aqueo
9、us solution(See Note1 and Note 2.) Dissolve 22.0 g of NaOH in water and dilute to1 L. Allow to stand overnight. Siphon the liquid into a cleanbottle. Standardize accurately to 60.001 N with potassium acidphthalate. The standardized sodium hydroxide solution shouldbe protected against evaporation and
10、 absorption of carbondioxide (CO2) from the air.NOTE 3The normality of the hydrochloric acid and sodium hydroxidesolutions may be in the range of 0.5 6 0.05 N.7.4 Freshly boiled water, or equivalent. (See 6.2.)8. Precautions8.1 Hydrochloric acid and sodium hydroxide solutions arecorrosive. Avoid eye
11、 and skin contact.8.2 Prior to use, please study and be aware of the MaterialSafety Data Sheet and correct laboratory performance for theappropriate health and safety precautions that may apply to anyof the chemicals and equipment that are used in this procedure.8.3 It is the responsibility of each
12、organization to conduct ajob hazard analysis to assess all the safety risks and PPEneeded for performance of this test method.9. Procedure9.1 Weigh 50 6 0.1 g of a well-mixed glycerine sample intoa 200 to 250 mL Erlenmeyer flask.9.2 Dilute the sample with 50 mL of freshly boiled andcooled water.9.3
13、Add 5.00 6 0.1 mL of 0.5 N sodium hydroxide solutionto the flask using a pipette or automatic titrator. Gently swirlthe flask to ensure mixing.NOTE 4Ensure the glycerine sample, the water and the sodiumhydroxide solution are well mixed before refluxing, otherwise, bumpingand erratic boiling can occu
14、r.9.4 Add three to five boiling chips into the flask andsecurely place the fitted air condenser into the neck of the flask.Using a polytetrafluoroethylene (PTFE)4sleeve between theglass joint is suggested.NOTE 5When testing samples with expected high FA engine coolant; esters; ethylene; fatty acids;
15、glycerin; glycerine; glycerol; titrimetricASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and t
16、he riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision
17、of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shoul
18、dmake 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 obtain
19、ed by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 1 Fatty Acids and Esters in Glycerin (%)Material Average Std Dev RepeatabilityStd DevReproducibilityStd DevRepeatabilityLimitReproducibilityLimitx SxSrSRrRA 0.30 0.07 0.004 0.068 0.012 0.189B 0.54 0.05 0.009 0.047 0.025 0.131D7638 10 (2015)3
