ASTM D6470-99(2020)
(Test Method)Standard Test Method for Salt in Crude Oils (Potentiometric Method)
Standard Test Method for Salt in Crude Oils (Potentiometric Method)
SIGNIFICANCE AND USE
4.1 A knowledge of water extractable inorganic halides in oil is important when deciding whether or not the oils need desalting. Excessive halide, especially in crude oil, frequently results in higher corrosion rates in refining units.
SCOPE
1.1 This test method covers the determination of salt in crude oils. For the purpose of this test method, salt is expressed as % (m/m) NaCl (sodium chloride) and covers the range from 0.0005 % to 0.15 % (m/m).
1.2 The limit of detection is 0.0002 % (m/m) for salt (as NaCl).
1.3 The test method is applicable to nearly all of the heavier petroleum products, such as crude oils, residues, and fuel oils. It may also be applied to used turbine oil and marine diesel fuel to estimate seawater contamination. Water extractable salts, originating from additives present in oils, are codetermined.
1.4 The values stated in SI units are to be regarded as the standard.
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 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.
General Information
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Standards Content (Sample)
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: D6470 − 99 (Reapproved 2020)
Standard Test Method for
Salt in Crude Oils (Potentiometric Method)
This standard is issued under the fixed designation D6470; 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 D4057 Practice for Manual Sampling of Petroleum and
Petroleum Products
1.1 This test method covers the determination of salt in
D4177 Practice for Automatic Sampling of Petroleum and
crudeoils.Forthepurposeofthistestmethod,saltisexpressed
Petroleum Products
as % (m/m) NaCl (sodium chloride) and covers the range from
D4377 Test Method forWater in Crude Oils by Potentiomet-
0.0005 % to 0.15 % (m/m).
ric Karl Fischer Titration (Withdrawn 2020)
1.2 The limit of detection is 0.0002 % (m/m) for salt (as
D4928 Test Method for Water in Crude Oils by Coulometric
NaCl).
Karl Fischer Titration
1.3 The test method is applicable to nearly all of the heavier E200 Practice for Preparation, Standardization, and Storage
of Standard and Reagent Solutions for ChemicalAnalysis
petroleum products, such as crude oils, residues, and fuel oils.
Itmayalsobeappliedtousedturbineoilandmarinedieselfuel
3. Summary of Test Method
to estimate seawater contamination. Water extractable salts,
originating from additives present in oils, are codetermined. 3.1 After homogenizing the crude oil with a mixer, a
weighed aliquot is dissolved in xylene at 65 °C and extracted
1.4 The values stated in SI units are to be regarded as the
with specified volumes of alcohol, acetone, and water in an
standard.
electrically heated extraction apparatus. A portion of the
1.5 This standard does not purport to address all of the
aqueous extract is analyzed for total halides by potentiometric
safety concerns, if any, associated with its use. It is the
titration.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Significance and Use
mine the applicability of regulatory limitations prior to use.
4.1 A knowledge of water extractable inorganic halides in
1.6 This international standard was developed in accor-
oil is important when deciding whether or not the oils need
dance with internationally recognized principles on standard-
desalting. Excessive halide, especially in crude oil, frequently
ization established in the Decision on Principles for the
results in higher corrosion rates in refining units.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
5. Apparatus
Barriers to Trade (TBT) Committee.
5.1 Extraction Apparatus, made of borosilicate glass, con-
formingtothedimensionsgiveninFig.1,andconsistingofthe
2. Referenced Documents
following component parts:
2.1 ASTM Standards:
5.1.1 Boiling Flask, 500 mL capacity.
D329 Specification for Acetone
5.1.2 Hopkins Reflux Condenser, having a vapor outlet
D770 Specification for Isopropyl Alcohol
connected by a rubber tube to an outside vent or to a suction
D843 Specification for Nitration Grade Xylene
hood.
D1193 Specification for Reagent Water
5.1.3 Thistle Tube, approximately 70 mL capacity, with a
D4006 Test Method for Water in Crude Oil by Distillation
line to indicate approximately the 50 mL level.
5.1.4 Heating Tube, containing a chimney for increasing
convection in the liquid.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
5.1.5 Heating Coil, 250 W, consisting of a suitable gage of
Subcommittee D02.03 on Elemental Analysis.
Nichrome wire.
Current edition approved May 1, 2020. Published June 2020. Originally
5.1.6 Rheostat, of suitable resistance and capacity, for
approved in 1999. Last previous edition approved in 2015 as D6470 – 99 (2015).
DOI: 10.1520/D6470-99R20. regulating the heater.
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 last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6470 − 99 (2020)
NOTE 1—Hopkins-type condenser is used.
FIG. 1 Extraction Apparatus
5.2 Safety Shield, colorless safety glass, or equivalent, to be designscanalsobeusedprovidedtheperformanceconformsto
mounted in front of the extraction apparatus (see 5.1). the requirements described in Annex A1.
5.3 Sampling Tube, glass, length approximately 600 mm, 5.7 Oven, explosion-proof, temperature 65 °C 6 5 °C.
I.D. approximately 5 mm, with a bulb having a volume of
5.8 Filter Paper, Whatman No. 41, or equivalent.
100 mL, or more, and drawn out at one end to an opening of
5.9 Stopwatch.
inside diameter (I.D.) 2 mm to 3 mm.Apipette with cut-off tip
makes a suitable sample tube.
6. Reagents and Materials
5.4 Potentiometric Titration Equipment, with a measuring
6.1 Purity of Reagents—Unless otherwise indicated, it is
accuracy of 62 mV, or better, provided with a silver indicating
intended that all reagents shall conform to the specifications of
and a glass reference electrode and 10 mL burette, preferably
theCommitteeonAnalyticalReagentsoftheAmericanChemi-
pistontype.Ifanautomatictitratorisused,thisshallbecapable
cal Society where such specifications are available.
of adding fixed increments of titrant (see 9.3.3.2).
5.5 Magnetic Stirrer, with polytetrafluoroethylene (PTFE)-
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
coated stirring bar.
Standard-Grade Reference Materials, American Chemical Society, Washington,
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
5.6 Homogenizer. A mixer with counter-rotating blades
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
operating at approximately 3000 r⁄min (50/s) is usually suit-
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
able for homogenization of samples up to 500 mL. Other copeial Convention, Inc. (USPC), Rockville, MD.
D6470 − 99 (2020)
6.2 Purity of Water—For all purposes where water is 7.2 Laboratory Sample—The sample of crude oil presented
mentioned, reagent water of a suitable purity shall be used. tothelaboratoryortestfacilityforanalysisbythistestmethod.
Various types of reagent water are described in Specification Only representative samples obtained as specified in Practices
D1193. D4057 and D4177 shall be used for this test method.
7.3 Test Sample—The sample aliquot obtained from the
6.3 Acetone (2-propanone), conforming to Specification
D329.(Warning—Extremely flammable. Vapors may cause laboratory sample for analysis by this test method. Once
drawn, the entire portion of the test sample will be used in the
flashfire.)
analysis. Mix the laboratory sample properly, as described in
6.4 Alcohol, for example, 95 % (V/V) ethanol, or propan-
7.4, prior to drawing the test sample.
2–ol (isopropyl alcohol), conforming to Specification D770.
7.4 Homogenize the laboratory sample of crude oil imme-
(Warning—Flammable.)
diately (within 15 min) before drawing the test sample to
6.5 Barium Nitrate, A.R., crystals. (Warning—Barium
ensure complete homogeneity. Mix the sample at room tem-
compounds and their solutions present a health risk if incor-
perature (15 °C to 25 °C), or less, in the laboratory sample
rectly handled. Prevent all contact.)
container, and record the temperature of the sample in degrees
6.6 Hydrochloric Acid, 0.1 mol⁄L, aqueous. Add 9 mL of
Celsius immediately before mixing. Heat waxy samples, solid
A.R. concentrated hydrochloric acid (density 1.19 g⁄mL) to at room temperature, to 3 °C above their pour point in order to
1 L with water. (Warning—Corrosive. Causes skin burns.)
facilitate test sample withdrawal. Select the type of mixer
related to the quantity of crude oil in the laboratory sample
6.7 Nitric Acid, 5 mol⁄L, aqueous. Cautiously add 325 mL
container. Before any unknown mixer is used, the specifica-
of A.R. concentrated nitric acid (density 1.42 g⁄mL) to 1 L
tions for the homogenization test (see AnnexA1) shall be met.
water, while stirring. (Warning—Corrosive. Causes skin
Reevaluate the mixer for any changes in the type of crude, the
burns.)
quantity of crude, the shape of the sample container, or the
6.8 Silver Nitrate Solution, standard, c(AgNO)=
mixing conditions (such as mixing speed and time of mixing).
0.1 mol⁄L, aqueous. Prepare, standardize and store as de-
7.5 For small laboratory sample containers and volumes,
scribed in Practice E200 for 0.1 N aqueous solution, reading
50 mL to 500 mL, a nonaerating, high speed (3000 r⁄min),
concentrations in mol/L in place of normality. Restandardize
shear mixer is required. Use the mixing time, mixing speed,
regularly, but in any case before preparation of the standard
and height above the bottom of the container found to be
0.01 mol⁄L solution (see 6.9)
satisfactory to Annex A1. For larger containers and volumes,
NOTE 1—Alternatively, ampoules containing concentrated solutions for
appropriate mixing conditions shall be defined by following a
preparation of standard volumetric solutions are available from various
set of procedures similar to those outlined in Annex A1 and
suppliers. (Warning—Silver compounds and their solutions present a
Practice D4177 but modified for application to the larger
health risk if incorrectly handled. Prevent all contact.)
containers and volumes. Clean and dry the mixer between
6.9 Silver Nitrate Solution, standard, c(AgNO)=
samples.
0.01 mol⁄L, aqueous. Prepare shortly before use by accurately
7.6 Record the temperature of the sample immediately after
diluting one volume of the recently restandardized 0.1 mol⁄L
homogenization. The rise in temperature between this reading
silver nitrate solution (Warning—see 6.8) to a tenfold volume
andtheinitialreadingpriortomixing(see7.4)shallnotexceed
with water.
10 °C, otherwise excessive loss of volatile vapors can occur or
6.10 Sodium Chloride Solution, approximately 1 mmol⁄L,
the dispersion can become unstable.
aqueous.Dissolve59 mg 61 mgsodiumchloridein1 Lwater.
7.7 In order to ensure that crude oils with rapidly settling
6.11 Xylene, conforming to Specification D843.
impurities are properly sampled, withdraw the test sample
(Warning—Xylene presents a health risk if incorrectly
container immediately after homogenization by lowering the
handled.Avoid inhalation. Extract vapor by working in a fume
tip of the sample tube (see 5.3) almost to the bottom of the
cupboard.)
container, and withdrawing the test sample as quickly as
possible. Clean and dry the sample tube before and after
6.12 Lead Acetate Paper.
sampling.
6.13 Polishing Paper, 800 grit, or finer, to polish the silver
electrode.
8. Preparation of Apparatus
8.1 Extraction Apparatus—To reduce the risk of superheat-
7. Sampling and Sample Preparation
ing and the resulting hazards, introduce a gentle stream of air
7.1 Sampling is defined as all the steps required to obtain an intothebottomoftheextractionapparatus.Thiscanbedoneby
aliquotrepresentativeofthecontentsofanypipe,tank,orother passing a length of hypodermic tubing through the bore of the
system, and to place the sample into the laboratory sample tap so that the lower end reaches the bottom of the heating
container. The laboratory sample container and sample volume tube, while the upper end of the tubing is passed through a
shall be of sufficient dimensions and volume to allow mixing, rubber bung in the top of the thistle tube. Place the extraction
as described in 7.4.(Warning—The results of the round robin apparatus behind a safety screen. Shield all electrical resis-
have shown that for reliable results, strict adherence to the tances and devices; alternatively, remove them from the
sampling and mixing procedure is of the utmost importance.) immediate vicinity of the extraction apparatus.
D6470 − 99 (2020)
8.2 Potentiometric Titration Equipment: 9.3.2 Fill the burette with 0.01 mol⁄Lsilver nitrate solution,
8.2.1 Glass Electrode—Before each titration (or each series place the beaker on a magnetic stirrer, and immerse the
of titrations), rinse the electrode with water and soak it for at electrodesinthesamplesolution.Immersethetipoftheburette
least 10 min in 0.1 mol⁄L hydrochloric acid (see 6.6). Then approximately 25 mm below the liquid surface, and adjust the
rinse again with water. After titrations store the electrode magnetic stirrer to produce vigorous stirring without spatter-
immersed in reagent water. ing.
8.2.2 Silver Electrode—Polish the silver electrode before
9.3.3 Titrate as follows:
each set of titrations with polishing paper (see 6.13) until a
9.3.3.1 When applying manual titration, record the initial
clean, polished metal surface is obtained.
burettereadingandthepH/millivoltmeterreading.Titratewith
standard silver nitrate solution, adding the titrant in small
9. Procedure portions.Aftereachaddition,waituntilaconstantpotentialhas
been established and record the burette and meter readings (see
9.1 Extraction:
Note 4). In regions between inflections where the potential
9.1.1 Weigh about 40 g of sample, to the nearest 0.1 g, into
change is small for each increment of silver nitrate used, add
a 250 mL beaker and heat on a water bath or in an oven to
volumes as large as 0.5 mL. When the rate of change of
65 °C 6 5 °C. Heat 40 mL 6 1 mL of xylene to the same
potential becomes greater than 5 mV per 0.1 mL, use 0.1 mL
temperature and add slowly to the sample while stirring
increments of silver nitrate solution. Construct a graph by
constantly until dissolution is complete. Transfer the solution
plotting the meter readings versus the volumes of standard
quantitatively to the extraction apparatus, rinsing the beaker
silver nitrate solution used in the titration.
with two separate portions of 15 mL 6 1 mLof hot xylene and
adding these rinsings also to the extraction apparatus.
NOTE4—Ifsilverhalidesareprecipitatedonthesilverelectrode,tapthe
9.1.2 While the solution is still hot, add 25 mL 61mLof electrode gently to dislodge the clinging precipitate and ensure that an
equilibrium has been
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