ASTM D94-07(2017)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D94 −07 (Reapproved 2017)
Designation: 136S1/98, 136S2/99
Standard Test Methods for
Saponification Number of Petroleum Products
ThisstandardisissuedunderthefixeddesignationD94;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 These test methods cover the determination of the
responsibility of the user of this standard to establish appro-
amount of constituents in petroleum products such as
priate safety and health practices and determine the applica-
lubricants, additives, and transmission fluids that will saponify
bility of regulatory limitations prior to use. For specific hazard
under the conditions of the test.
statements, see Sections 6, 7, 8, 10, 15, 16, 17, and 19.
NOTE1—Statementsdefiningthistestanditssignificancewhenapplied
1.5 This international standard was developed in accor-
toelectricalinsulatingoilsofmineraloriginwillbefoundinGuideD117.
dance with internationally recognized principles on standard-
Experience has shown that for transformer oils, Test Method D94,
ization established in the Decision on Principles for the
modified by use of 0.1 M KOH solution and 0.1 M HCl, is more suitable.
Development of International Standards, Guides and Recom-
1.1.1 Two test methods are described: Method A—Color
mendations issued by the World Trade Organization Technical
Indicator Titration (Sections 6–13), and Method
Barriers to Trade (TBT) Committee.
B—Potentiometric Titration (Sections14–23).
1.2 Because compounds of sulfur, phosphorus, the 2. Referenced Documents
halogens, and certain other elements that are sometimes added
2.1 ASTM Standards:
to petroleum products also consume alkali and acids, the
D117Guide for Sampling, Test Methods, and Specifications
results obtained indicate the effect of these extraneous materi-
for Electrical Insulating Oils of Petroleum Origin
als in addition to the saponifiable material present. Results on
D128Test Methods for Analysis of Lubricating Grease
products containing such materials, on used internal-
D1193Specification for Reagent Water
combustion-engine crankcase oils, and on used turbine oils
D4057Practice for Manual Sampling of Petroleum and
must be interpreted with caution.
Petroleum Products
NOTE 2—The materials referred to above, which are not normally D4177Practice for Automatic Sampling of Petroleum and
considered saponifiable matter, include inorganic or certain organic acids,
Petroleum Products
most nonalkali soaps, and so forth. The presence of such materials
D6299Practice for Applying Statistical Quality Assurance
increases the saponification number above that of fatty saponifiable
and Control Charting Techniques to Evaluate Analytical
materials for which the test method is primarily intended. The odor of
Measurement System Performance
hydrogen sulfide near the end of the back-titration in the saponification
test is an indication that certain types of reactive sulfur compounds are D6792Practice for Quality Management Systems in Petro-
present in the sample. In the case of other reactive sulfur, chlorine, and
leum Products, Liquid Fuels, and Lubricants Testing
phosphorus compounds and other interfering materials, no simple indica-
Laboratories
tion is given during the test. A gravimetric determination of the actual
amount of fatty acids is probably the most reliable method for such 2.2 Energy Institute Standards:
compounds. Test Methods D128 or IP Method284/86 can be used to
IP 136Method of Test for Saponification Number of Petro-
determine fatty acids gravimetrically.
leum Products
1.3 The values stated in SI units are to be regarded as the IP 284Method of Test for Fatty Acids
standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
These test methods are under the jurisdiction of ASTM Committee D02 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Petroleum Products, Liquid Fuels, and Lubricants and are the direct responsibility Standards volume information, refer to the standard’s Document Summary page on
of Subcommittee D02.06 on Analysis of Liquid Fuels and Lubricants. the ASTM website.
CurrenteditionapprovedMay1,2017.PublishedJuly2017.Originallyapproved Available from Institute of Petroleum, 61 New Cavendish St., London, W.I.,
ɛ1
in 1921. Last previous edition approved in 2007 as D94–07 (2012) . DOI: England.Available from Energy Institute, 61 New Cavendish St., London, WIG
10.1520/D0094-07R17. 7AR, U.K., http://www.energyinst.org.uk.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D94 − 07 (2017)
3. Terminology 7. Reagents
3.1 Definitions: 7.1 Purity of Reagents—Reagent grade chemicals shall be
3.1.1 saponification number, n—the number of milligrams used in all tests. Unless otherwise indicated, it is intended that
ofpotassiumhydroxideconsumedby1gofasampleunderthe all reagents shall conform to the specifications of the Commit-
conditions of the test. tee onAnalytical Reagents of theAmerican Chemical Society,
3.1.1.1 Discussion—Thevalueofthesaponificationnumber where such specifications are available. Other grades may be
in these test methods can be affected by the presence of other used, provided it is first ascertained that the reagent is of
alkali-reactive species, as described in Note 2. sufficiently high purity to permit its use without lessening the
accuracy of the determination.
3.1.2 saponify, v—to hydrolyze a fat with alkali to form an
alcohol and the salt of a fatty acid.
NOTE 4—Commercially available reagents may be used in place of
laboratory preparations, provided they meet the specifications outlined.
4. Summary of Test Method
7.2 Purity of Water—Unless otherwise indicated, references
4.1 A known mass of the sample is dissolved in a suitable to water shall be understood to mean reagent water as defined
solvent, such as butanone (methylethylketone), xylenes, or by Type I, II, or III in Specification D1193.
Stoddard Solvent, or a combination thereof (Warning—
7.3 Alcohol —95 % ethanol (Warning—Flammable.
Extremely flammable. Vapors can cause flash fire), and is
Denatured—Cannot be made nontoxic) (see Note 5) and
heatedwithaknownamountofalcoholicpotassiumhydroxide
(Warning—Flammable) or 95% ethanol to which has been
(KOH).Theexcessalkaliistitratedwithstandardacid,andthe
added10%byvolumeofmethanol(seeNote5andNote6)or
saponification number is calculated.
absolute alcohol.
4.2 The titration end point can be detected either colori-
NOTE 5—It has been found that 99% 2-propanol (isopropyl alcohol)
metrically (Method A) or potentiometrically (Method B).
canbesubstitutedforthepurifiedethanolwithentirelysatisfactoryresults.
This substitution is not permissible, however, in referee tests.
5. Significance and Use
NOTE 6—This composition is available under the name of “U.S.
Department ofTreasury Specially Denatured Formula 30 (Regulation No.
5.1 Petroleumproductscancontainadditivesthatreactwith
3-1938).” Formula 3A plus 5% methanol is an equivalent.
alkalitoformmetalsoaps.Fatsareexamplesofsuchadditives.
7.4 Aqueous Hydrochloric Acid Standard Solution
Also, certain used engine oils, especially from turbine or
(0.5 M)—Standardize to detect molarity changes of 0.0005 by
internal combustion engines, can contain chemicals that will
titrating with standard alcoholic KOH solution (see 7.8 and
similarly react with alkali. The saponification number ex-
Note 7).
presses the amount of base that will react with 1g of sample
whenheatedinaspecificmanner.Thisthengivesanestimation
NOTE7—Wheresaponificationnumbersbelowoneareexpected,better
precisioncanbeobtainedbysubstituting0.1 MKOHsolutionandHClfor
of the amount of acid present in the sample, that is, any free
the 0.5 M reagents in Sections 7, 8, 10, 17, and 19.
acid originally present plus any combined (for example, in
7.5 Butanone (Methyl Ethyl Ketone), technical grade. Store
esters) that have been converted to metal soaps during the
heating procedure. in dark or brown bottles. (Warning—See 4.1.)
7.6 Naphtha, (Warning—Extremely flammable. Harmful if
5.2 Saponification numbers are also used in setting product
specifications for lubricants and additives. inhaled. Vapors can cause flash fire.) ASTM Precipitation
Grade (or Petroleum Spirit-60/80 or hexanes) (Warning—
METHOD A—COLOR INDICATOR TITRATION
Combustible. Vapor harmful.) Petroleum spirit shall conform
to the current IP 136.
6. Apparatus
7.7 Phenolphthalein Solution, Neutralized—Dissolve 1.0g
6.1 Erlenmeyer Flask and Condenser— An Erlenmeyer
6 0.1g of phenolphthalein in 100mL of alcohol (see 7.3).
flask, 250mLor 300mLcapacity, alkali-resistant (see Note 3)
Neutralize to faint pink color with dilute (0.1 M) alcoholic
and (Warning—Causes severe burns; a recognized carcino-
KOH solution.
gen; strong oxidizer—contact with other material can cause
7.8 Alcoholic Potassium Hydroxide Standard Solution (0.5
fire; hygroscopic ), to which is attached a straight or
M)—Prepareapproximately0.5 MsolutionbydissolvingKOH
mushroom-type reflux condenser. The straight-type condenser
in the alcohol specified in 7.3.Allow the solution to settle in a
is fitted to the flask with a ground-glass joint; the mushroom-
dark place. Filter the solution, and allow to stand for 24 h
type condenser must fit loosely to permit venting of the flask.
before using.
Water reflux condensers can also be used instead of air
condensers.
Reagent Chemicals, American Chemical Society Specifications, American
NOTE 3—Do not use scratched or etched Erlenmeyer flasks because
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
KOH will react with them. The glassware shall be chemically clean. It is
listed by the American Chemical Society, see Annual Standards for Laboratory
recommended that flasks be cleaned with chromic acid cleaning solution
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
(Alternatively, Nochromix or similar products can be used.)
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD.
6.2 Hot Plate—A suitable hot plate heated by either elec-
Available from the U.S. Bureau of Alcohol, Tobacco, and Firearms, Distilled
tricity or steam. (Warning—Thermal hazard; in addition to
Spirits and Tobacco Branch, 1200 Pennsylvania Avenue, NW, Washington, DC
other precautions, avoid contact with exposed skin.) 20226.
D94 − 07 (2017)
7.8.1 Alternatively, prepare 0.5 M or 0.1 M alcoholic KOH restores the color, continue the titration, making further drop-
by mixing a commercially available KOH ampule (which is wise additions of indicator, if necessary, until the end point is
carbonate free) with 95% alcohol. Using this type solution reached(Note14).Theendpointisreachedwhentheindicator
gives consistent blanks and does not give multiple breaks (see color is completely discharged and does not immediately
Note 8). reappear upon further dropwise addition of the indicator
solution. Record as V in 11.1.
NOTE 8—Because of the relatively large coefficient of cubic expansion
of organic liquids such as 2-propanol (isopropyl alcohol), the standard
NOTE 14—Avoid emulsification of titration mixture, but ensure phase
alcoholic solution has to be standardized at temperatures close to those
contact by swirling the flask vigorously as the end point is approached.
employed in the titrations of samples.
7.8.2 The KOH solutions shall be standardized by titrating
9. Sample
with standard potassium hydrogen phthalate solution (see 7.9
9.1 Using Practice D4057 (manual sampling) or Practice
and Note 8).
D4177 (automatic sampling) as a guideline for obtaining a
7.9 Potassium Hydrogen Phthalate—(C H KO ) 0.1 M
8 5 4
representativesample,makesurethattheportionofthesample
Standard Solution —Weigh 2.0422g 6 0.0002g of potassium
to be tested appears homogenous. Choose the size of the
hydrogen phthalate that has been dried at 110°C 65°Ctoa
sample so that the back-titration volume is from 40 to 80% of
constant weight into a 100mL volumetric flask. Dissolve in
the blank, but do not exceed a 20g sample weight (see Note
reagent water. Some heating may be necessary to dissolve the
15).
solid. Dilute to 100mLwith distilled or deionized water, after
NOTE 15—The following sample sizes are suggested:
the solution has cooled.
Saponification Number Sample Size, g
7.10 Stoddard Solvent, technical grade. (Warning—
181 to 400 1
Extremely flammable. Harmful if inhaled.)
111 to 180 2
71 to 110 3
7.11 Xylene, reagent grade. (Warning—Extremely flam-
31 to 70 5
mable. Harmful if inhaled.) 16 to 30 10
0to15 20
8. Blank Determinations
10. Procedure
8.1 Perform a blank determination concurrently with each
10.1 Weigh the specimen to the nearest 0.01g (record as W
set (see Note 9) (one or more) of samples as follows: measure
in 11.1), such as by difference, from a small beaker into the
accurately from a buret or volumetric pipet (see Note 10) into
Erlenmeyer flask. Add 25mL 6 1mL of butanone or one of
the Erlenmeyer flask 25mL 6 0.03mL of alcoholic KOH
the alternative solvents (Warning—See 4.1), followed by
solution and 25mL 6 1mLof butanone (methylethyl-ketone)
25mL 6 0.03mLof alcoholic KOH solution (Warning—See
oroneofthealternativesolvents.Connectthecondensertothe
7.3) measured accurately from a buret or volumetric pipet (see
flask,andheatforthesameamountoftimeasthatusedforthe
Note 7).
sample after refluxing begins. (Warning—The reflux con-
denser should be clamped securely to prevent it from tipping
10.2 Dissolve the difficult to dissolve samples, such as
over onto the hot plate with possible breakage of glassware.
lubricants and additives, first in 15mL to 25mL of Stoddard
See also Note 11. ) Immediately add 50mLofASTM precipi-
Solvent(Warning—See7.10)orxylene(Warning—See7.11)
tation naphtha (Warning—See 7.6, also Note 12 and Note 13)
before adding butanone (Warning—See 4.1).
by cautiously pouring the naphtha down the condenser (dis-
10.3 Connect the condenser to the flask and heat for 30min
connect condenser if mushroom-type is used), and titrate the
afterrefluxingbegins(seeNote11).Immediatelyadd50mLof
blank while hot, without reheating, with 0.5 M hydrochloric
ASTM precipitation naphtha (Warning—Do not pour naphtha
acid (HCl) using three drops of neutralized phenolphthalein
while the flask is on the hot plate) and (see 7.6) by cautiously
indicator solution.
pouring the naphtha down the condenser (see Note 12)
NOTE 9—Run blank determinations in duplicate on samples requiring
(disconnect condenser if mushroom-type before adding the
the highest accuracy. The precision data are based on duplicate blank
naphtha).
determinations. A single blank is sufficient for routine work.
NOTE 10—If a volumetric pipet is used to measure the alcoholic KOH
10.4 Titrate the solution while hot (without reheating) with
solution, wait 30s after delivery to allow for complete drainage.
0.5 M HCl using three drops of neutralized phenolphthalein
NOTE11—Althoughstandardprocedurerequires30minofreflux,some
indicator solution (Warning—See 7.3). When the indicator
fats are readily saponified and complete saponification takes place within
10min. On the other hand, difficult saponifiable materials require more color is discharged, add, dropwise, more indicator solution. If
than2h.Neithertheshortenedperiodnorthelongerperiodshouldbeused
this addition of indicator restores the color, continue the
except by mutual consent of the interested parties.
titration, making further dropwise additions of indicator, if
NOTE 12—Pouring 50mLof naphtha down the condenser at the end of
necessary, until the end point is reached (Note 14). The end
thesaponificationnotonlyrinsesthecondenserbutalsocoolsthereaction
point is reached when the indicator color is completely
mixture.
NOTE 13—In the case of insulating oils, the addition of ASTM
discharged and does not immediately reappear upon further
precipitation naphtha or petroleum spirit is not necessary.
dropwise addition of the indicator solution. (Record as V in
8.2 After the indicator color has been discharged, add, 11.1.) When testing waxes, it may be necessary to reheat the
dropwise, more indicator solution. If this addition of indicator solutionduringtitrationtopreventsolidificationofthesample.
D94 − 07 (2017)
11. Calculation would in the long run, in the normal and correct operation of
the test method, exceed the Fig. 1 values only in one case in
11.1 Calculate the saponification number, A, as follows:
twenty.
A 556.1 M V 2 V /W (1)
~ !
1 2
13.1.2 Reproducibility—The difference between two single
and independent results obtained by different operators work-
where:
ingindifferentlaboratoriesonidenticaltestmaterialswould,in
M = molarity of the hydrochloric acid,
the long run, in the normal and correct operation of the test
V = volume of acid used in titrating the blank, mL,
method, exceed the Fig. 1 values only in one case in twenty.
V = volume of acid used in titrating the sample, mL,
W = sample, g, and
13.2 Bias—This is an empirical test method, and there are
56.1 = molecular weight of KOH.
no accepted reference materials that can be compared; hence,
bias cannot be determined.
12. Report
METHOD B—POTENTIOMETRIC TITRATION
12.1 For saponification numbers of less than 50, report the
saponification number to the nearest 0.5mg KOH⁄g sample.
14. Apparatus
12.2 For saponification number of 50 or more, report to the
14.1 Erlenmeyer Flask and Condenser— An Erlenmeyer
nearest whole number.
flask,250mLor300mLcapacity,alkali-resistant(seeNote3),
12.3 For electrical insulating oils, report the values to the
to which is attached a straight or mushroom-type reflux
nearest 0.1mg KOH/g sample.
condenser. The straight-type condenser is fitted to the flask
12.4 Report the saponification numbers as obtained by Test with a ground-glass joint; the mushroom-type condenser must
Methods D94, Method A. fitlooselytopermitventingoftheflask.Waterrefluxcondens-
ers can also be used instead of air condensers.
13. Precision and Bias
14.2 Hot Plate—A suitable hot plate heated by either
13.1 Precision—The data shown in Fig. 1 shall be used for
electricity or steam (see 6.2).
judging the acceptability of results (95% probability) (see
14.3 Potentiometric Titrator Automatic, Recording or
Note 16).
Manual—High-precision titrator capable of distinguishing the
NOTE 16—No precision intervals can be given for highly colored new
carbonate from pure caustic in the titration of ACS reagent
or used oils, or for oils that produce dark-colored solutions upon
grade KOH by hydrochloric acid (HCl).
saponification,ascolorcaninterferewiththedetectionoftheendpointof
the titration. In such cases, potentiometric titration (Method B) can be 14.4 Electrodes—High-quality electrodes must be used.
used.
Cleaning and maintenance of the electrodes are vital to their
satisfactory operation.
13.1.1 Repeatability—The difference between two test
14.4.1 Combination Glass Electrode, or a suitable glass
results, obtained by the same operator with the same apparatus
electrode and a suitable reference electrode; either silver
under constant operating conditions on identical test material,
chloride (AgCl)/saturated alcoholic lithium chloride (LiCl) or
saturated potassium chloride (KCl) inverted glass sleeve calo-
mel electrode can be used.
14.5 Magnetic Stirring Bars—Because, on titration, two
immiscibleliquidphasesappear,andpotassiumchloride(KCl)
is precipitated, stirring conditions are critical, and very vigor-
ous stirring is essential (see Note 17).
NOTE 17—If a large magnetic stir bar is used, only slow speeds are
possible, and if too small a stir bar is used, the highest rotational speeds
cause insufficient agitation of the bulk of the liquid. The optimum
magnetic stir bar has been found to be a 2.5cm by 0.5cm plain
polytetrafluoroethylene (PTFE)-coated cylinder. This magnetic stirrer is
not needed if a propeller or paddle stirrer is used.
14.6 Tall Form Beakers—250mLor 300mLsize Berzelius
type tall-form glass beaker with or without a spout (see Note
18).
NOTE 18—The potent
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