ASTM D5558-95(2006)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D5558 – 95 (Reapproved 2006)
Standard Test Method for
Determination of the Saponification Value of Fats and Oils
This standard is issued under the fixed designation D5558; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Procedure
1.1 This test method covers the determination of the saponi- 4.1 Melt the sample, if not already liquid, and filter through
fication value of fats and oils. filter paper to remove any impurities and the last traces of
1.2 The values stated in SI units are to be regarded as the moisture. The sample must be completely dry.
standard. 4.2 Accurately weigh a sample, of such size (usually 4 to 5
1.3 This standard does not purport to address all of the g) that the back titration is 45 to 55 % of the blank, and 50 mL
safety concerns, if any, associated with its use. It is the of the alcoholic KOH is added with a pipette, allowing the
responsibility of the user of this standard to establish appro- pipette to drain for a definite period of time.
priate safety and health practices and determine the applica- 4.2.1 Prepare a blank determination and conduct simulta-
bility of regulatory limitations prior to use. neously with the sample.
4.3 Connect air condensers to the flask and boil the solution
2. Significance and Use
gently but steadily until the sample is completely saponified.
2.1 This test method is intended for use in the determination
This usually requires approximately 1 h for normal samples.
of the saponification value of fats and oils used in the Take care that the vapor ring in the condenser does not rise to
manufacture of fat liquors for the purpose of quality assurance.
the top of the condenser or there may be some loss.
NOTE 1—Some samples particularly difficult to saponify may require
3. Apparatus and Reagents
more than 1 h. This can only be determined by trial. Clarity and
3.1 Erlenmeyer Flasks, Corning alkali resistant, Kimble
homogeneity of the test solution are partial indicators of the complete
resistant, or equivalent, 250 or 300 mL.
saponification, but they are not necessarily absolute criteria.
3.2 Air Condensers, minimum length 650 mm.
4.4 After the flask and condenser have cooled somewhat,
3.3 Water Bath or a Hot Plate, with variable heat control.
but not sufficiently to jell the contents, wash down the inside of
3.4 Hydrochloric Acid, 0.5 N, accurately standardized.
the condenser with a little distilled water. Then disconnect the
3.5 Alcoholic Potassium Hydroxide, added to a 2-L flask
flask, add approximately 1 mL of indicator, and titrate the
from 1 to 1.5 L of 95 % ethyl alcohol (U.S.S.D. Formula 3A
solution with 0.5 N HCl until the pink color has just disap-
is permitted) and a few grams (5 to 10 g) of potassium
peared.
hydroxide. After boiling under a reflux condenser on a water
bath for 30 to 60 min, the alcohol shall be distilled an
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