ASTM D94-07(2012)

Standard Test Methods for Saponification Number of Petroleum Products

SIGNIFICANCE AND USE
5.1 Petroleum products can contain additives that react with alkali to form metal soaps. Fats are examples of such additives. Also, certain used engine oils, especially from turbine or internal combustion engines, can contain chemicals that will similarly react with alkali. The saponification number expresses the amount of base that will react with 1 g of sample when heated in a specific manner. This then gives an estimation of the amount of acid present in the sample, that is, any free acid originally present plus any combined (for example, in esters) that have been converted to metal soaps during the heating procedure.  
5.2 Saponification numbers are also used in setting product specifications for lubricants and additives.
SCOPE
1.1 These test methods cover the determination of the amount of constituents in petroleum products such as lubricants, additives, and transmission fluids that will saponify under the conditions of the test. Note 1—Statements defining this test and its significance when applied to electrical insulating oils of mineral origin will be found in Guide D117. Experience has shown that for transformer oils, Test Method D94, modified by use of 0.1  M KOH solution and 0.1 M HCl, is more suitable.  
1.1.1 Two test methods are described: Method A—Color Indicator Titration (Sections 6-13), and Method B—Potentiometric Titration (Sections 14-23).  
1.2 Because compounds of sulfur, phosphorus, the halogens, and certain other elements that are sometimes added to petroleum products also consume alkali and acids, the results obtained indicate the effect of these extraneous materials in addition to the saponifiable material present. Results on products containing such materials, on used internal-combustion-engine crankcase oils, and on used turbine oils must be interpreted with caution. Note 2—The materials referred to above, which are not normally considered saponifiable matter, include inorganic or certain organic acids, most nonalkali soaps, and so forth. The presence of such materials increases the saponification number above that of fatty saponifiable materials for which the test method is primarily intended. The odor of hydrogen sulfide near the end of the back-titration in the saponification test is an indication that certain types of reactive sulfur compounds are present in the sample. In the case of other reactive sulfur, chlorine, and phosphorus compounds and other interfering materials, no simple indication is given during the test. A gravimetric determination of the actual amount of fatty acids is probably the most reliable method for such compounds. Test Methods D128 or IP Method 284/86 can be used to determine fatty acids gravimetrically.  
1.3 The values stated in SI units are to be regarded as the standard.  
1.4 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. For specific hazard statements, see Sections 6, 7, 8, 10, 15, 16, 17, and 19.

General Information

• Status: Historical
• Publication Date: 31-Oct-2012
• ICS: 75.080 - Petroleum products in general
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.06 - Analysis of Liquid Fuels and Lubricants

Relations

• Replaces: ASTM D94-07 - Standard Test Methods for Saponification Number of Petroleum Products
• Effective Date: 01-Nov-2012
• Replaced By: ASTM D94-07(2012)e1 - Standard Test Methods for Saponification Number of Petroleum Products
• Effective Date: 01-Nov-2012
• Referred By: ASTM D4056-21 - Standard Test Method for Estimation of Solubility of Water in Hydrocarbon and Aliphatic Ester Lubricants
• Effective Date: 01-Nov-2012
• Referred By: ASTM D6710-21 - Standard Guide for Evaluation of Hydrocarbon-Based Quench Oil
• Effective Date: 01-Nov-2012

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D94 −07(Reapproved 2012)
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 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
toelectricalinsulatingoilsofmineraloriginwillbefoundinGuideD117.
2. Referenced Documents
Experience has shown that for transformer oils, Test Method D94,
2.1 ASTM Standards:
modified by use of 0.1 M KOH solution and 0.1 M HCl, is more suitable.
D117Guide for Sampling,Test Methods, and Specifications
1.1.1 Two test methods are described: Method A—Color
for Electrical Insulating Oils of Petroleum Origin
Indicator Titration (Sections 6-13), and Method
D128Test Methods for Analysis of Lubricating Grease
B—Potentiometric Titration (Sections 14-23).
D1193Specification for Reagent Water
1.2 Because compounds of sulfur, phosphorus, the
D4057Practice for Manual Sampling of Petroleum and
halogens, and certain other elements that are sometimes added
Petroleum Products
to petroleum products also consume alkali and acids, the
D4177Practice for Automatic Sampling of Petroleum and
results obtained indicate the effect of these extraneous materi-
Petroleum Products
als in addition to the saponifiable material present. Results on
D6299Practice for Applying Statistical Quality Assurance
products containing such materials, on used internal-
and Control Charting Techniques to Evaluate Analytical
combustion-engine crankcase oils, and on used turbine oils
Measurement System Performance
must be interpreted with caution.
D6792Practice for Quality System in Petroleum Products
NOTE 2—The materials referred to above, which are not normally and Lubricants Testing Laboratories
considered saponifiable matter, include inorganic or certain organic acids,
2.2 Energy Institute Standards:
most nonalkali soaps, and so forth. The presence of such materials
IP 136Method of Test for Saponification Number of Petro-
increases the saponification number above that of fatty saponifiable
leum Products
materials for which the test method is primarily intended. The odor of
hydrogen sulfide near the end of the back-titration in the saponification IP 284Method of Test for Fatty Acids
test is an indication that certain types of reactive sulfur compounds are
present in the sample. In the case of other reactive sulfur, chlorine, and
3. Terminology
phosphorus compounds and other interfering materials, no simple indica-
3.1 Definitions:
tion is given during the test. A gravimetric determination of the actual
amount of fatty acids is probably the most reliable method for such
3.1.1 saponification number, n—the number of milligrams
compounds. Test Methods D128 or IP Method284/86 can be used to
ofpotassiumhydroxideconsumedby1gofasampleunderthe
determine fatty acids gravimetrically.
conditions of the test.
1.3 The values stated in SI units are to be regarded as the
3.1.1.1 Discussion—Thevalueofthesaponificationnumber
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 [e-mail]. For Annual Book of ASTM
Petroleum Products and Lubricants and are the direct responsibility of Subcommit- Standards volume information, refer to the standard’s Document Summary page on
tee D02.06 on Analysis of Lubricants. the ASTM website.
Current edition approved Nov. 1, 2012. Published November 2012. Originally Available from Institute of Petroleum, 61 New Cavendish St., London, W.I.,
approved in 1921. Last previous edition approved in 2007 as D94–07. DOI: England.Available from Energy Institute, 61 New Cavendish St., London, WIG
10.1520/D0094-07R12. 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 (2012)
in these test methods can be affected by the presence of other where such specifications are available. Other grades may be
alkali-reactive species, as described in Note 2. used, provided it is first ascertained that the reagent is of
sufficiently high purity to permit its use without lessening the
3.1.2 saponify, v—to hydrolyze a fat with alkali to form an
accuracy of the determination.
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—
Extremely flammable. Vapors can cause flash fire), and is
7.3 Alcohol —95 % ethanol (Warning—Flammable.
heatedwithaknownamountofalcoholicpotassiumhydroxide
Denatured—Cannot be made nontoxic) (see Note 5) and
(KOH).Theexcessalkaliistitratedwithstandardacid,andthe
(Warning—Flammable) or 95% ethanol to which has been
saponification number is calculated.
added 10 volume % of methanol (see Note 5 and Note 6)or
absolute alcohol.
4.2 The titration end point can be detected either colori-
metrically (Method A) or potentiometrically (Method B).
NOTE 5—It has been found that 99% 2-propanol (isopropyl alcohol)
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.
5.1 Petroleumproductscancontainadditivesthatreactwith Department ofTreasury Specially Denatured Formula 30 (Regulation No.
3-1938).” Formula 3A plus 5% methanol is an equivalent.
alkalitoformmetalsoaps.Fatsareexamplesofsuchadditives.
Also, certain used engine oils, especially from turbine or
7.4 Aqueous Hydrochloric Acid Standard Solution (0.5
internal combustion engines, can contain chemicals that will
M)—Standardize to detect molarity changes of 0.0005 by
similarly react with alkali. The saponification number ex-
titrating with standard alcoholic KOH solution (see 7.8 and
presses the amount of base that will react with1gof sample
Note 7).
whenheatedinaspecificmanner.Thisthengivesanestimation
NOTE7—Wheresaponificationnumbersbelowoneareexpected,better
of the amount of acid present in the sample, that is, any free
precisioncanbeobtainedbysubstituting0.1 MKOHsolutionandHClfor
acid originally present plus any combined (for example, in
the 0.5 M reagents in Sections 7, 8, 10, 17, and 19.
esters) that have been converted to metal soaps during the
7.5 Butanone (Methyl Ethyl Ketone) ,technicalgrade.Store
heating procedure.
in dark or brown bottles. (Warning— See 4.1.)
5.2 Saponification numbers are also used in setting product
7.6 Naphtha, (Warning— Extremely flammable. Harmful
specifications for lubricants and additives.
if 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 1.0 6
6.1 Erlenmeyer Flask and Condenser— An Erlenmeyer
0.1 g of phenolphthalein in 100 mL of alcohol (see 7.3).
flask,250or300-mLcapacity,alkali-resistant(seeNote3)and
Neutralize to faint pink color with dilute (0.1 M) alcoholic
(Warning—Causes severe burns; a recognized carcinogen;
KOH solution.
strong oxidizer—contact with other material can cause fire;
7.8 Alcoholic Potassium Hydroxide Standard Solution (0.5
hygroscopic ), to which is attached a straight or mushroom-
type reflux condenser. The straight-type condenser is fitted to M)—Prepareapproximately0.5 MsolutionbydissolvingKOH
in the alcohol specified in 7.3.Allow the solution to settle in a
the flask with a ground-glass joint; the mushroom-type con-
denser must fit loosely to permit venting of the flask. Water dark place. Filter the solution, and allow to stand for 24 h
before using.
reflux condensers can also be used instead of air condensers.
7.8.1 Alternatively prepare 0.5 or 0.1 M alcoholic KOH by
NOTE 3—Do not use scratched or etched Erlenmeyer flasks because
mixing a commercially available KOH ampule (which is
KOH will react with them. The glassware shall be chemically clean. It is
carbonate free) with 95% alcohol. Using this type solution
recommended that flasks be cleaned with chromic acid cleaning solution
(Alternatively, Nochromix or similar products can be used.) gives consistent blanks and does not give multiple breaks (see
Note 8).
6.2 Hot Plate—A suitable hot plate heated by either elec-
tricity or steam. (Warning—Thermal hazard; in addition to
other precautions, avoid contact with exposed skin.) 4
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
listed by the American Chemical Society, see Annual Standards for Laboratory
7. Reagents
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
7.1 Purity of Reagents—Reagent grade chemicals shall be
MD.
used in all tests. Unless otherwise indicated, it is intended that
Available from the U.S. Bureau of Alcohol, Tobacco, and Firearms, Distilled
all reagents shall conform to the specifications of the Commit-
Spirits and Tobacco Branch, 1200 Pennsylvania Avenue, NW, Washington, DC
tee onAnalytical Reagents of theAmerican Chemical Society, 20226.
D94 − 07 (2012)
NOTE 8—Because of the relatively large coefficient of cubic expansion NOTE 14—Avoid emulsification of titration mixture, but ensure phase
of organic liquids such as 2-propanol (isopropyl alcohol), the standard contact by swirling the flask vigorously as the end point is approached.
alcoholic solution has to be standardized at temperatures close to those
employed in the titrations of samples.
9. Sample
7.8.2 The KOH solutions shall be standardized by titrating
9.1 Using Practice D4057 (manual sampling) or Practice
with standard potassium hydrogen phthalate solution (see 7.9
D4177 (automatic sampling) as a guideline for obtaining a
and Note 8).
representativesample,makesurethattheportionofthesample
to be tested appears homogenous. Choose the size of the
7.9 Potassium Hydrogen Phthalate—(C H KO ) 0.1 M
8 5 4
sample so that the back-titration volume is from 40 to 80% of
Standard Solution —Weigh 2.0422 6 0.0002 g of potassium
the blank, but do not exceed a 20-g sample weight (see Note
hydrogen phthalate that has been dried at 110 6 5°C to a
15).
constant weight into a 100-mL volumetric flask. Dissolve in
reagent water. Some heating may be necessary to dissolve the
NOTE 15—The following sample sizes are suggested:
solid. Dilute to 100 mLwith distilled or deionized water, after
Saponification Number Sample Size, g
the solution has cooled.
181 to 400 1
111 to 180 2
7.10 Stoddard Solvent, technical grade. (Warning—
71 to 110 3
Extremely flammable. Harmful if inhaled.)
31 to 70 5
16 to 30 10
7.11 Xylene, reagent grade. (Warning—Extremely flam-
0to15 20
mable. Harmful if inhaled.)
10. Procedure
8. Blank Determinations
10.1 Weigh the specimen to the nearest 0.01 g (record as W
8.1 Perform a blank determination concurrently with each
in 11.1), such as by difference, from a small beaker into the
set (see Note 9) (one or more) of samples as follows: measure
Erlenmeyer flask. Add 25 6 1 mL of butanone or one of the
accurately from a buret or volumetric pipet (see Note 10) into
alternative solvents (Warning—See 4.1), followed by 25 6
theErlenmeyerflask25 60.03mLofalcoholicKOHsolution
0.03 mL of alcoholic KOH solution (Warning—See 7.3)
and 256 1 mLof butanone (methylethyl-ketone) or one of the
measuredaccuratelyfromaburetorvolumetricpipet(seeNote
alternative solvents. Connect the condenser to the flask, and
7).
heat for the same amount of time as that used for the sample
10.2 Dissolve the difficult to dissolve samples, such as
after refluxing begins. (Warning—The reflux condenser
lubricants and additives, first in 15 to 25 mL of Stoddard
shouldbeclampedsecurelytopreventitfromtippingoveronto
Solvent (Warning— See 7.10) or xylene (Warning—See
the hot plate with possible breakage of glassware. See also
7.11) before adding butanone (Warning—See 4.1).
Note 11. ) Immediately add 50 mL of ASTM precipitation
naphtha (Warning— See 7.6, also Note 12 and Note 13)by
10.3 Connect the condenser to the flask and heat for 30 min
cautiously pouring the naphtha down the condenser (discon-
afterrefluxingbegins(seeNote11).Immediatelyadd50mLof
nectcondenserifmushroom-typeisused),andtitratetheblank
ASTM precipitation naphtha (Warning—Do not pour naphtha
while hot, without reheating, with 0.5 M hydrochloric acid
while the flask is on the hot plate) and (see 7.6) by cautiously
(HCl) using three drops of neutralized phenolphthalein indica-
pouring the naphtha down the condenser (see Note 12)
tor solution.
(disconnect condenser if mushroom-type before adding the
naphtha).
NOTE 9—Run blank determinations in duplicate on samples requiring
the highest accuracy. The precision data are based on duplicate blank
10.4 Titrate the solution while hot (without reheating) with
determinations. A single blank is sufficient for routine work.
0.5 M HCl using three drops of neutralized phenolphthalein
NOTE 10—If a volumetric pipet is used to measure the alcoholic KOH
indicator solution (Warning—See 7.3). When the indicator
solution, wait 30 s after delivery to allow for complete drainage.
color is discharged, add, dropwise, more indicator solution. If
NOTE11—Althoughstandardprocedurerequires30minofreflux,some
fa
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