ASTM D3227-00
(Test Method)Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
SCOPE
1.1 This test method covers the determination of mercaptan sulfur in gasolines, kerosines, aviation turbine fuels, and distillate fuels containing from 0.0003 to 0.01 mass% of mercaptan sulfur. Organic sulfur compounds such as sulfides, disulfides, and thiophene do not interfere. Elemental sulfur in amounts less than 0.0005 mass % does not interfere. Hydrogen sulfide will interfere, if not removed as described in 9.2.
1.2 The values in acceptable SI units are to be regarded as the standard. The values in parentheses are for information only.
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 health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Sections 6, 8, and 9.
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NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 3227 – 00 An American National Standard
Designation: 342/93
Standard Test Method for
(Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation
Turbine, and Distillate Fuels (Potentiometric Method)
This standard is issued under the fixed designation D 3227; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
This test method has been approved by the sponsoring committee and accepted by the cooperation societies in accordance with
established procedures.
1. Scope Petroleum Products
D 6299 Practice for Applying Statistical Quality Assurance
1.1 This test method covers the determination of mercaptan
Techniques to Evaluate Analytical Measurement System
sulfur in gasolines, kerosines, aviation turbine fuels, and
Performance
distillate fuels containing from 0.0003 to 0.01 mass % of
mercaptan sulfur. Organic sulfur compounds such as sulfides,
3. Summary of Test Method
disulfides, and thiophene, do not interfere. Elemental sulfur in
3.1 The hydrogen sulfide-free sample is dissolved in an
amounts less than 0.0005 mass % does not interfere. Hydrogen
alcoholic sodium acetate titration solvent and titrated potentio-
sulfide will interfere if not removed, as described in 9.2.
metrically with silver nitrate solution (see Note 1), using as an
1.2 The values in acceptable SI units are to be regarded as
indicator the potential between a glass reference electrode and
the standard. The values in parentheses are for information
a silver/silver-sulfide indicating electrode. Under these condi-
only.
tions, the mercaptan sulfur is precipitated as silver mercaptide
1.3 This standard does not purport to address all of the
and the end point of the titration is shown by a large change in
safety concerns, if any, associated with its use. It is the
cell potential.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4. Significance and Use
bility of regulatory limitations prior to use. For specific hazard
4.1 Mercaptan sulfur has an objectionable odor, an adverse
statements, see Sections 6, 8, and 9.
effect on fuel system elastomers, and is corrosive to fuel
2. Referenced Documents system components.
2.1 ASTM Standards:
5. Apparatus
D 1193 Specification for Reagent Water
3 5.1 As described in 5.2-5.5; alternatively, any automatic
D 1250 Guide for Petroleum Measurement Tables
titration system may be used that, using the same electrode pair
D 1298 Test Method for Density, Relative Density (Specific
described in 5.3, is capable of performing the titration as
Gravity), or API Gravity of Crude Petroleum and Liquid
3 described in Section 9 and selecting the endpoint specified in
Petroleum Products by Hydrometer Method
11.1 with a precision that meets or is better than that given in
D 4052 Test Method for Density and Relative Density of
4 Section 13.
Liquids by Digital Density Meter
5.2 Meter—An electronic voltmeter, operating on an input
D 4057 Practice for Manual Sampling of Petroleum and
−12
4 of less than 9 3 10 A and having a sensitivity of 62mV
Petroleum Products
over a range of at least 61 V. The meter shall be electrostati-
D 4177 Practice for Automatic Sampling of Petroleum and
cally shielded, and the shield shall be connected to the ground.
5.3 Cell System, consisting of a reference and indicating
electrode. The reference electrode should be a sturdy, pencil-
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee type glass electrode, having a shielded lead connected to
D02.03 on Elemental Analysis.
ground. The indicating electrode shall be made from a silver
Current edition approved Nov. 10, 2000. Published November 2000. Originally
published as D 3227 – 73. Last previous edition D 3227 – 99.
Annual Book of ASTM Standards, Vol 11.01.
3 5
Annual Book of ASTM Standards, Vol 05.01. Annual Book of ASTM Standards, Vol 05.04.
4 6
Annual Book of ASTM Standards, Vol 05.02. Any apparatus that will give equal or better precision will be acceptable.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 3227
wire, 2 mm (0.08 in.) in diameter or larger, mounted in an 6.6.1 Standardization—Add six drops of concentrated
insulated support. Silver billet electrodes can also be used. HNO (rel dens 1.42) (Warning—Poison. Causes severe burns.
5.4 Buret, 10-mL capacity, graduated in 0.05-mL intervals, Harmful or fatal if swallowed or inhaled.) to 100 mL of water
with a tip that extends approximately 120 mm (5 in.) below the in a 300-mL tall-form beaker. Remove oxides of nitrogen by
stopcock. boiling for 5 min. Cool to ambient temperature. Pipet 5 mL of
5.5 Titration Stand, preferably built as an integral part of the 0.1 mol/L KI solution into the beaker and titrate with the
meter housing and provided with supports for the electrodes AgNO solution choosing the end point at the inflection of the
and electrical stirrer, all connected to ground. No permanent titration curve.
change in meter reading should be noticeable upon connecting 6.7 Silver Nitrate, Standard Alcoholic Solution (0.010 mol/
or disconnecting the stirring motor. L)—Prepare daily when the test is being performed by dilution
of the 0.1 N standard. Pipet 100 mL of the 0.1 mol/L standard
6. Reagents and Materials
into a 1-L volumetric flask and dilute to volume with propan-
6.1 Purity of Reagents—Reagent grade chemicals shall be
2-ol. Calculate the exact molarity.
used in all tests. Unless otherwise indicated, it is intended that
6.8 Sodium Sulfide Solution (10 g/L)—Dissolve 10 g of
all reagents shall conform to the specifications of the Commit-
Na S in water and dilute to 1 L with water. Prepare fresh as
tee on Analytical Reagents of the American Chemical Society,
needed.
where such specifications are available. Other grades may be
6.9 Sulfuric Acid, dilute. Cautiously dilute five volumes of
used, provided it is first ascertained that the reagent is of
water with one volume of sulfuric acid (Sp.Gr.1.84). (Warning
sufficiently high purity to permit its use without lessening the
Adding the acid will generate heat: mix well. If water begins to
accuracy of the determination.
boil, cool before adding more acid. Note that only limited
6.1.1 Commercially available solutions may be used in
volumes are required because only 10 mL are needed for each
place of prepared laboratory solutions, when they are certified
litre of cadmium sulfate solution.
to meet the required concentrations.
6.10 Titration Solvent—Low molecular weight mercaptans,
6.1.2 Alternate volumes of solutions and solvents may be
as usually found in gasoline, are readily lost from the titration
prepared, when an equivalent concentration is maintained.
solution if an acidic titration solvent is used. For the determi-
6.2 Water—Reagent grade, Type I, Specification D 1193.
nation of the higher molecular weight mercaptan as normally
6.3 Cadmium Sulfate, Acid Solution (150 g/L)—Dissolve
encountered in kerosines, aviation turbine fuels, and distillate
150 g of cadmium sulfate (3CdSO 3 8H O) in water.
4 2
fuels, the acidic titration solvent is used to achieve more rapid
(Warning—Poison. May be fatal if swallowed or inhaled. A
equilibrium between successive additions of the titrant.
known carcinogen (animal positive).) Add 10 mL of dilute
6.10.1 Alkaline Titration Solvent—Dissolve 2.7 g of sodium
H SO ( Warning—Poison. Causes severe burns. Harmful or
2 4
acetate trihydrate (NaC H O ·3H O) or 1.6 g of anhydrous
2 3 2 2
fatal if swallowed or inhaled.) and dilute to 1 L with water.
sodium acetate (NaC H O ) in 25 mL of water free of
2 3 2
6.4 Potassium Iodide, Standard Solution (approximately 0.1
dissolved oxygen and pour into 975 mL of propan-2-ol (99 %)
mol/L)—Dissolve 17 g of KI (weigh to 0.01 g) in 100 mL of
(Note 1). When necessary, remove dissolved oxygen by purg-
water in a 1-L volumetric flask and dilute to 1 L. Calculate the
ing the solution with a rapid stream of nitrogen for 10 min each
exact molarity.
day prior to use; keep protected from the atmosphere. To
6.5 2-Propanol—( Warning—Flammable.). Warning—
minimize oxygen from dissolving in the solution during
Unless inhibited against it, peroxides can form in 2-propanol
storage, an option exists to nitrogen blanket the solution prior
when stored in the same container that is exposed to air. When
to sealing the solvent container.
this happens and the propan-2-ol evaporates to dryness, an
6.10.2 Acidic Titration Solvent—Dissolve 2.7 g of
explosion can occur. When peroxides are suspected, they may
NaC H O ·3H Oor1.6gofNaC H O in 20 mL of water free
2 3 2 2 2 3 2
be removed by percolation through an activated alumina
of dissolved oxygen and pour into 975 mL of propan-2-ol
column.
(99 %) (Note 1) and add 4.6 mL of glacial acetic acid. When
6.6 Silver Nitrate, Standard Alcoholic Solution (0.1 mol/
necessary, remove dissolved oxygen by purging the solution
L)—Dissolve 17 g of AgNO in 100 mL of water in a 1-L
with a rapid stream of nitrogen for 10 min each day prior to
volumetric flask and dilute to 1 L with 2-propanol (99 %) (see
use; keep protected from the atmosphere. To minimize oxygen
Note 1). Store in a dark bottle and standardize at intervals
from dissolving in the solution during storage, an option exists
frequent enough to detect a change of 0.0005 or greater in
to nitrogen blanket the solution prior to sealing the solvent
molarity.
container.
6.11 Polishing Paper or Cloth, 16–20 μm average particle
NOTE 1—It is important to pass the propan-2-ol through a column of
activated alumina to remove peroxides that may have formed on storage; size abrasive.
failure to remove peroxides will lead to low results. It is not necessary to
7. Sampling
perform this step if the alcohol is tested and found free of peroxides.
7.1 Take the sample in accordance with Practice D 4057 or
Practice D 4177.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
7.2 Methanethiol (methyl mercaptan) has a boiling point of
listed by the American Chemical Society, see Analar Standards for Laboratory
6.2°C and may be expected to be present in light untreated
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
gasolines. Therefore, when the presence of this low boiling
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. thiol (mercaptan) is known or expected, specimen to be tested
D 3227
elemental sulfur, which, when heated under total reflux conditions, may
shall be kept below 4°C to prevent the loss of mercaptan from
produce H S by the inter-reaction of both. This phenomenon is particu-
such samples.
larly noticed in straight run gasolines produced from some natural gas
8. Preparation of Apparatus condensates. Therefore, it is advisable that during the removal of H S (and
after all H S has been extracted), that no heat should be applied to the
8.1 Glass Electrode—After each manual titration, or batch
sample.
of titrations, in the case of automatic titration systems, wipe the
9.2.1 When the test results obtained are not for referee
electrode with a soft, clean tissue and rinse with water. Clean
purposes and Quality Assurance/Quality Control (QA/QC)
the electrode at frequent intervals (at least once a week) by
protocol permits, an alternative test for, and a procedure for the
stirring in cold chromic acid solution (Warning—Causes
removal of, hydrogen sulfide can be used. This process uses
severe burns. A recognized carcinogen. Strong oxidizer—
lead acetate paper and sodium hydrogen carbonate and is
contact with other material may cause fire. Hygroscopic. An
described in Appendix X1.
equivalent, chromium-free cleaning solution may be used.) for
9.2.2 For referee purposes, the protocol, as detailed in 9.2,
a few seconds (10 s maximum). When not in use, keep lower
shall be used. A possible non-referee situation may be the
half of the electrode immersed in water.
instance of routine refinery control.
8.2 Silver/Silver-Sulfide Electrode— Each day prior to use,
9.3 Measure with a pipet or weigh 20 to 50 mL of the
prepare a fresh silver sulfide coating on the electrode by the
original or treated sample into an appropriately sized beaker
following method:
(for example, a 200, 250, or 300 mL size beaker is typically
8.2.1 Burnish electrode with polishing paper or cloth until a
large enough) containing 100 mL of the appropriate titration
clean, polished silver surface shows.
solvent. Place the beaker on the titration stand or on the
8.2.2 Place electrode in operating position and immerse it in
auto-sampler of an automatic titration system. If an automatic
100 mL of titration solvent containing 8 mL of Na S solution.
titration system is used, set up the system to reproduce the
8.2.3 Add slowly from a buret, with stirring, 10 mL of 0.1
experimental conditions specified in 9.3.1, 9.3.2, and 9.3.3.
mol/L AgNO solution over a period from 10 to 15 min.
Adjust the position of the titration stand so that the electrodes
8.2.4 Remove electrode from solution, wash with water, and
are about half immersed. Fill the buret with 0.01 mol/L
wipe with a soft, clean tissue.
alcoholic AgNO solution and position it in the titration
8.2.5 Between manual titrations, or batches of titrations in 3
assembly so that the tip extends approximately 25 mm (1 in.)
the case of automatic titration systems, store the electrode a
below the surface of the liquid in the beaker. Adjust the speed
minimum of 5 min in 100 mL of titration solvent containing 0.5
of the stirrer to give vigorous stirring without spattering.
mL of the 0.1 mol/L AgNO solution.
9.3.1 Record the initial buret and cell potential readings.
9. Procedure
The usual meter readings for mercaptan presence are in
9.1 Determination of Density—If the sample is to be mea- the −250 mV to −350 mV range. Add suitable small portions of
sured volumetrically, determine the density by Test Method 0.01 mol/L AgNO solution and, after waiting until a constant
D 1298 or D 4052 at the temperature at which the test portion potential has been established, record the buret and meter
will be taken, either directly or from the density determined at
readings. Consider the potential constant if it changes less than
a reference temperature and conv
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