ASTM D3242-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D3242 − 11 (Reapproved 2017) D3242 − 23
Designation: 354/98354/09
Standard Test Method for
1,2
Acidity in Aviation Turbine Fuel
This standard is issued under the fixed designation D3242; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 This test method covers the determination of the acidity in aviation turbine fuel in the range from 0.000 mg ⁄g to 0.100 mg ⁄g
KOH.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration
D1193 Specification for Reagent Water
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.1.2 acid number, n—the quantity of a specified base, expressed in milligrams of potassium hydroxide per gram of sample,
required to titrate a sample in a specified solvent to a specified endpoint using a specified detection system.
This test method is under the jurisdiction of ASTM International Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility
of ASTM Subcommittee D02.06 on Analysis of Liquid Fuels and Lubricants. The technically equivalent standard as referenced is under the jurisdiction of the Energy Institute
Subcommittee SC-B-11.
Current edition approved May 1, 2017Nov. 1, 2023. Published June 2017November 2023. Originally approved in 1973. Last previous edition approved in 20112017 as
D3242 – 11.D3242 – 11 (2017). DOI: 10.1520/D3242-11R17. 10.1520/D3242-23.
This test method has been approved by the sponsoring committees and accepted by the cooperating societies in accordance with established procedures.
This test method has been developed through the cooperative effort between ASTM and the Energy Institute, London. ASTM and IP standards were approved by ASTM
and EI technical committees as being technically equivalent but that does not imply both standards are identical.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3242 − 23
3.1.2.1 Discussion—
in this test method, the solvent is a toluene-water-isopropanol mixture and the end point is determined when a green/green brown
color is obtained using the specified p-naphtholbenzein indicator solution.
4. Summary of Test Method
4.1 The sample is dissolved in a mixture of toluene and isopropyl alcohol containing a small amount of water. The resulting single
phase solution is blanketed by a stream of nitrogen bubbling through it and is titrated with standard alcoholic potassium hydroxide
to the end point indicated by the color change (orange in acid and green in base) of the added p-naphtholbenzein solution.
5. Significance and Use
5.1 Some acids can be present in aviation turbine fuels due either to the acid treatment during the refining process or to naturally
occurring organic acids. Significant acid contamination is not likely to be present because of the many check tests made during
the various stages of refining. However, trace amounts of acid can be present and are undesirable because of the consequent
tendencies of the fuel to corrode metals that it contacts or to impair the water separation characteristics of the aviation turbine fuel.
5.2 This test method is designed to measure the levels of acidity that can be present in aviation turbine fuel and is not suitable
for determining significant acid contamination.
6. Apparatus
6.1 Buret—A 25 mL buret graduated in 0.1 mL subdivisions, or a 10 mL buret graduated in 0.05 mL subdivisions.
NOTE 1—An automated buret capable of delivering titrant amounts in 0.05 mL or smaller increments can be used, but the stated precision data were
obtained using manual burets only.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
NOTE 2—Commercially available reagents may be used in place of laboratory preparations when they are certified in accordance with 7.1.
7.2 Purity of Water— References to water shall be understood to mean distilled water as defined by Type III water of Specification
D1193.
5,6
7.3 p-Naphtholbenzein Indicator Solution—The p-naphtholbenzein must meet the specifications given in Annex A1. Prepare a
solution of p-naphtholbenzein in titration solvent equal to 10 g ⁄L 6 0.01 g ⁄L.
7.4 Nitrogen, dry-type, carbon dioxide-free. (Warning—Compressed gas under high pressure. Gas reduces oxygen available for
breathing.)
7.5 Potassium Hydroxide Solution, Standard Alcoholic (0.01 N)—Add 0.6 g of solid KOH (Warning—Highly corrosive to all
body tissue both in solid form and in solution.) to approximately 1 L of anhydrous isopropyl alcohol (Warning—Flammable.
Vapor harmful. Keep away from heat, sparks, and open flame.) (containing less than 0.9 % water) in a 2 L Erlenmeyer flask. Boil
the mixture gently for 10 min to 15 min, stirring to prevent the solids from forming a cake on the bottom. Add at least 0.2 g of
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For Suggestionssuggestions on the testing of reagents not listed by the American Chemical Society, see
AnnualAnalar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial
Convention, Inc. (USPC), Rockville, MD.
In a 2006 study, only Kodak, Baker (Mallinkrodt), Fluka, and Aldrich were found to meet the specifications in Annex A1. However, Kodak brand is no longer available.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1626. Contact ASTM Customer
Service at service@astm.org.
D3242 − 23
FIG. 1 Titration Flask
barium hydroxide (Ba(OH) ) (Warning—Poisonous if ingested. Strongly alkaline, causes severe irritation producing dermatitis.)
and again boil gently for 5 min to 10 min. Cool to room temperature, allow to stand for several hours, and filter the supernatant
liquid through a fine sintered-glass or porcelain filtering funnel; avoid unnecessary exposure to carbon dioxide (CO ) during
filtration. Store the solution in a chemically resistant dispensing bottle out of contact with cork, rubber, or saponifiable stopcock
lubricant and protected by a guard tube containing soda lime.
NOTE 3—Because of the relative large coefficient of cubic expansion of organic liquids, such as isopropyl alcohol, the standard alcoholic solutions should
be standardized at temperatures close to those employed in the titration of samples.
7.5.1 Standardization of Potassium Hydroxide Solution—Standardize frequently enough to detect changes of 0.0002N. One way
to accomplish this is as follows. Weigh, to the nearest 0.1 mg, approximately 0.02 g of potassium acid phthalate, which has been
dried for at least 1 h at 110 °C 6 1 °C and dissolve in 40 mL 6 1 mL of water, free of CO . Titrate with the potassium hydroxide
alcoholic solution to either of the following end points: (1) when the titration is electrometric, titrate to a well-defined inflection
point at the voltage that corresponds to the voltage of the basic buffer solution; (2) when the titration is colorimetric, add 6 drops
of phenolphthalein indicator solution and titrate to the appearance of a permanent pink color. Perform the blank titration on the
water used to dissolve the potassium acid phthalate. Calculate the normality using the equation:
W 1000
p
Normality 5 × (1)
204.23 V 2 V
b
where:
W = weight of the potassium acid phthalate, g,
p
204.23 = molecular weight of the potassium acid phthalate,
V = volume of titrant used to titrate the salt to the specific end point, mL, and
V = volume of titrant used to titrate the blank, mL.
b
7.5.2 Phenolphthalein Indicator Solution—Dissolve 0.1 g 6 0.01 g of pure solid phenolphthalein in 50 mL of water, free of CO ,
and 50 mL of ethanol.
7.6 Titration Solvent—Add 500 mL of toluene (Warning—Flammable. Vapor harmful. Keep away from heat, sparks, and open
flame.) and 5 mL of water to 495 mL of anhydrous isopropyl alcohol.
8. Procedure
8.1 Introduce 100 g 6 5 g of the sample weighed to the nearest 0.5 g, into a 500 mL wide-mouth Erlenmeyer flask. (One type of
suitable modified flask is shown in Fig. 1.) Add 100 mL of the titration solvent and 0.1 mL of the indicator solution. Introduce
nitrogen through a 6 mm to 8 mm outside diameter glass tube to a point within 5 mm of the flask bottom at a rate of 600 mL ⁄min
to 800 mL ⁄min. Bubble the solution for 3 min 6 30 s with occasional mixing.
D3242 − 23
8.1.1 The vapor from this treatment contains toluene and should be removed with adequate ventilation.
8.2 Continue the nitrogen addition and titrate without delay at a temperature below 30 °C. Add 0.01 N KOH solution in increments
and swirl to disperse. When the solution first turns green, reduce the increment size to dropwise (manual buret) or between 0.01 mL
and 0.05 mL (automated buret). Continue until a persistent green end point is reached and held for a minimum of 15 s after the
addition of the last increment.
NOTE 4—The temperature can be measured by any suitable temperature measuring device.
8.3 Blank—Perform a blank titration on 100 mL of the titration solvent and 0.1 mL of the indicator solution, introducing the
nitrogen in the same manner and titrating to the same end point as above.
9. Quality Control Checks
9.1 Confirm the performance of the equipment or the procedure each day it is in use, by analyzing a quality control (QC) sample.
It is advisable to analyze additional QC samples as appropriate, such as at the end of a batch of samples or after a fixed number
of samples to ensure the quality of the results. Analysis of result(s) from these QC samples can be carried out using control chart
techniques. When the QC sample result causes the laboratory to be in an out-of-control situation, such as exceeding the
laboratory’s control limits, instrument recalibration may be required. An ample supply of QC sample material shall be available
for the intended period of use, and shall be homogeneous and stable under the anticipated storage conditions. If possible, the QC
sample shall be representative of samples typically analyzed and the average value and control limits of the QC sample shall be
determined prior to monitoring the measurement process. The QC sample precision shall be checked against the ASTM method
precision to ensure data quality.
NOTE 5—Because the acid number can vary while the QC sample is in storage, when an out-of-control situation arises, the stability of the QC sample
can be a source of the error.
10. Calculations
10.1 Calculate the acid number as follows:
Acid number, mg of KOH/g5 A 2 B N ×56.1 /W (2)
@~ ! #
where:
A = KOH solution required for titration of the sample (8.2), mL,
B = KOH solution required for titration of the blank (8.3), mL,
N = normality of the KOH solution, and
W = sample used, g.
11. Report
11.1 Report the result to the nearest 0.001 mg KOH ⁄g as Acid Number (Test Method D3242) = (Result).
12. Precision and Bias
12.1 Precision—The precision of this test method as determined by statistical examination of interlaboratory results is as follows:
12.1.1 Repeatability—The difference between two test results, obtained by the same operator with the same apparatus under
constant operating conditions on identical test material, would in the long run, in the normal and correct operation of the test
method, exceed the following values only in one case in twenty (see Table 1).
12.1.2 Reproducibility—The difference between two single and independent results obtained by different operators working in
MNL 7, Manual on Presentation of Data Control Chart Analysis, Section 3: Control Charts for Individuals, 6th ed., ASTM International, W. Conshohocken, 1990.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1010. Contact ASTM Customer
Service at service@astm.org.
D3242 − 23
A
TABLE 1 Precision
NOTE 1—All values are in acid number units.
Average Acid Number Repeatability Reproducibility
0.001 0.0004 0.0013
0.002 0.0006 0.0018
0.005 0.0009 0.0029
0.010 0.0013 0.0041
0.020 0.0019 0.0057
0.050 0.0030 0.0091
0.100 0.0042 0.0128
A
These precision data were derived as follows:
Repeatability 50.0132 a
œ
Reproducibility 50.0406 a
œ
where: a = acid number
different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method,
exceed the following values only in one case in twenty (see Table 1).
NOTE 6—The precision statements were based on the use of manual burets only. The user is cautioned that the precision statements may or may not be
applicable to titrations performed with the use of automated burets, since no interlaboratory study has been conducted to date to statistically evalua
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