ASTM-D7638 › Standard Test Method for Determination of Fatty Acids and Esters in Glycerin
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Scope
1.1 This test method provides the quantitative determination of the fatty acid and ester content in purified glycerin by the titrimetric method.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard may involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautions are listed in Section 8.
Significance and Use
Any residual fatty acid and esters (FA&E) should be present only at very low levels in purified glycerine.
This procedure requires the addition of a measured volume of sodium hydroxide, in excess of the amount actually needed to react with FA&E in the glycerine sample. After boiling, the excess sodium hydroxide is back titrated with standardized hydrochloric acid. The quantity of the substance being titrated is calculated as the difference between the volumes of the sodium hydroxide solution originally added, corrected by means of a blank titration, and that was consumed by the titrant in the back titration.
Note 1—The standardized solutions for sodium hydroxide and hydrochloric acid are commercially available.
Keywords
antifreeze; engine coolant; ethylene; esters; fatty acids; glycerin; glycerine; glycerol; titrimetric; ICS Number Code 71.080.60 (Alcohols. Ethers)
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Document Number
ASTM-D7638-10R21
Revision Level
2010 R21 EDITION
Status
Current
Modification Type
New
Publication Date
Sept. 1, 2021
Document Type
Test Method
Page Count
3 pages
Committee Number
D15.93