ASTM D6470-99(2004)
(Test Method)Standard Test Method for Salt in Crude Oils (Potentiometric Method)
Standard Test Method for Salt in Crude Oils (Potentiometric Method)
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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:D6470–99 (Reapproved 2004)
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 D4928 Test Methods for Water in Crude Oils by Coulom-
etric Karl Fischer Titration
1.1 This test method covers the determination of salt in
E200 Practice for Preparation, Standardization, and Storage
crudeoils.Forthepurposeofthistestmethod,saltisexpressed
of Standard and Reagent Solutions for Chemical Analysis
as % (m/m) NaCl (sodium chloride) and covers the range from
0.0005 to 0.15 % (m/m).
3. Summary of Test Method
1.2 The limit of detection is 0.0002 % (m/m) for salt (as
3.1 After homogenizing the crude oil with a mixer, a
NaCl).
weighed aliquot is dissolved in xylene at 65°C and extracted
1.3 The test method is applicable to nearly all of the heavier
with specified volumes of alcohol, acetone, and water in an
petroleum products, such as crude oils, residues, and fuel oils.
electrically heated extraction apparatus. A portion of the
Itmayalsobeappliedtousedturbineoilandmarinedieselfuel
aqueous extract is analyzed for total halides by potentiometric
to estimate seawater contamination. Water extractable salts,
titration.
originating from additives present in oils, are codetermined.
1.4 The values stated in SI units are to be regarded as the
4. Significance and Use
standard.
4.1 A knowledge of water extractable inorganic halides in
1.5 This standard does not purport to address all of the
oil is important when deciding whether or not the oils need
safety concerns, if any, associated with its use. It is the
desalting. Excessive halide, especially in crude oil, frequently
responsibility of the user of this standard to establish appro-
results in higher corrosion rates in refining units.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
5. Apparatus
5.1 Extraction Apparatus, made of borosilicate glass, con-
2. Referenced Documents
formingtothedimensionsgiveninFig.1,andconsistingofthe
2.1 ASTM Standards:
following component parts:
D329 Specification for Acetone
5.1.1 Boiling Flask, 500 mL capacity.
D770 Specification for Isopropyl Alcohol
5.1.2 Hopkins Reflux Condenser, having a vapor outlet
D843 Specification for Nitration Grade Xylene
connected by a rubber tube to an outside vent or to a suction
D1193 Specification for Reagent Water
hood.
D4006 Test Method for Water in Crude Oil by Distillation
5.1.3 Thistle Tube, approximately 70 mL capacity, with a
D4057 Practice for Manual Sampling of Petroleum and
line to indicate approximately the 50 mL level.
Petroleum Products
5.1.4 Heating Tube, containing a chimney for increasing
D4177 Practice for Automatic Sampling of Petroleum and
convection in the liquid.
Petroleum Products
5.1.5 Heating Coil, 250 W, consisting of a suitable gage of
D4377 Test Method for Water in Crude Oils by Potentio-
Nichrome wire.
metric Karl Fischer Titration
5.1.6 Rheostat, of suitable resistance and capacity, for
regulating the heater.
This test method is under the jurisdiction of ASTM Committee D02 on
5.2 Safety Shield, colorless safety glass, or equivalent, to be
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
mounted in front of the extraction apparatus (see 5.1).
D02.03 on Elemental Analysis.
5.3 Sampling Tube, glass, length approximately 600 mm,
Current edition approved May 1, 2004. Published June 2004. Originally
approved in 1999. Last previous edition approved in 1999 as D6470–99. DOI: I.D. approximately 5 mm, with a bulb having a volume of 100
10.1520/D6470-99R04.
mL, or more, and drawn out at one end to an opening of inside
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
diameter (I.D.) 2 to 3 mm. A pipette with cut-off tip makes a
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
suitable sample tube.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6470–99 (2004)
NOTE 1—Hopkins-type condenser is used.
FIG. 1 Extraction Apparatus
5.4 Potentiometric Titration Equipment, with a measuring theCommitteeonAnalyticalReagentsoftheAmericanChemi-
accuracyof 62mV,orbetter,providedwithasilverindicating cal Society where such specifications are available.
and a glass reference electrode and 10 mL burette, preferably 6.2 Purity of Water—For all purposes where water is
pistontype.Ifanautomatictitratorisused,thisshallbecapable mentioned, reagent water of a suitable purity shall be used.
of adding fixed increments of titrant (see 9.3.3.2). Various types of reagent water are described in Specification
5.5 Magnetic Stirrer, with polytetrafluoroethylene (PTFE)- D1193.
coated stirring bar. 6.3 Acetone (2-propanone), conforming to Specification
5.6 Homogenizer. A mixer with counter-rotating blades D329.(Warning—Extremely flammable. Vapors may cause
operatingatapproximately3000r/min(50/s)isusuallysuitable flashfire.)
for homogenization of samples up to 500 mL. Other designs 6.4 Alcohol, for example, 95 % (V/V) ethanol, or propan-
can also be used provided the performance conforms to the 2–ol (isopropyl alcohol), conforming to Specification D770.
requirements described in Annex A1. (Warning—Flammable.)
5.7 Oven, explosion-proof, temperature 65 6 5°C.
5.8 Filter Paper, Whatman No. 41, or equivalent.
5.9 Stopwatch. 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
6. Reagents and Materials
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
6.1 Purity of Reagents—Unless otherwise indicated, it is
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
intended that all reagents shall conform to the specifications of MD.
D6470–99 (2004)
6.5 Barium Nitrate, A.R., crystals. (Warning—Barium Celsius immediately before mixing. Heat waxy samples, solid
compounds and their solutions present a health risk if incor- at room temperature, to 3°C above their pour point in order to
rectly handled. Prevent all contact.) facilitate test sample withdrawal. Select the type of mixer
6.6 Hydrochloric Acid, 0.1 mol/L, aqueous. Add 9 mL of related to the quantity of crude oil in the laboratory sample
A.R.concentratedhydrochloricacid(density1.19g/mL)to1L container. Before any unknown mixer is used, the specifica-
with water. (Warning—Corrosive. Causes skin burns.) tions for the homogenization test (seeAnnexA1) shall be met.
6.7 Nitric Acid, 5 mol/L, aqueous. Cautiously add 325 mL Reevaluate the mixer for any changes in the type of crude, the
of A.R. concentrated nitric acid (density 1.42 g/mL) to 1 L quantity of crude, the shape of the sample container, or the
water, while stirring. (Warning—Corrosive. Causes skin mixing conditions (such as mixing speed and time of mixing).
burns.) 7.5 For small laboratory sample containers and volumes, 50
6.8 Silver Nitrate Solution, standard, c(AgNO ) = 0.1 to500mL,anonaerating,highspeed(3000r/min),shearmixer
mol/L, aqueous. Prepare, standardize and store as described in is required. Use the mixing time, mixing speed, and height
Practice E200 for 0.1 N aqueous solution, reading concentra- above the bottom of the container found to be satisfactory to
tions in mol/L in place of normality. Restandardize regularly, Annex A1. For larger containers and volumes, appropriate
but in any case before preparation of the standard 0.01 mol/L mixing conditions shall be defined by following a set of
solution (see 6.9) procedures similar to those outlined inAnnexA1 and Practice
D4177 but modified for application to the larger containers and
NOTE 1—Alternatively, ampoules containing concentrated solutions for
volumes. Clean and dry the mixer between samples.
preparation of standard volumetric solutions are available from various
7.6 Record the temperature of the sample immediately after
suppliers. (Warning—Silver compounds and their solutions present a
homogenization. The rise in temperature between this reading
health risk if incorrectly handled. Prevent all contact.)
andtheinitialreadingpriortomixing(see7.4)shallnotexceed
6.9 Silver Nitrate Solution, standard, c(AgNO ) = 0.01
10°C, otherwise excessive loss of volatile vapors can occur or
mol/L, aqueous. Prepare shortly before use by accurately
the dispersion can become unstable.
diluting one volume of the recently restandardized 0.1 mol/L
7.7 In order to ensure that crude oils with rapidly settling
silver nitrate solution (Warning—see 6.8) to a tenfold volume
impurities are properly sampled, withdraw the test sample
with water.
container immediately after homogenization by lowering the
6.10 Sodium Chloride Solution, approximately 1 mmol/L,
tip of the sample tube (see 5.3) almost to the bottom of the
aqueous. Dissolve 59 6 1 mg sodium chloride in 1 L water.
container, and withdrawing the test sample as quickly as
6.11 Xylene, conforming to Specification D843.
possible. Clean and dry the sample tube before and after
(Warning—Xylene presents a health risk if incorrectly
sampling.
handled.Avoid inhalation. Extract vapor by working in a fume
cupboard.)
8. Preparation of Apparatus
6.12 Lead Acetate Paper.
8.1 Extraction Apparatus—To reduce the risk of superheat-
6.13 Polishing Paper, 800 grit, or finer, to polish the silver
ing and the resulting hazards, introduce a gentle stream of air
electrode.
intothebottomoftheextractionapparatus.Thiscanbedoneby
passing a length of hypodermic tubing through the bore of the
7. Sampling and Sample Preparation
tap so that the lower end reaches the bottom of the heating
7.1 Sampling is defined as all the steps required to obtain an
tube, while the upper end of the tubing is passed through a
aliquotrepresentativeofthecontentsofanypipe,tank,orother
rubber bung in the top of the thistle tube. Place the extraction
system, and to place the sample into the laboratory sample
apparatus behind a safety screen. Shield all electrical resis-
container. The laboratory sample container and sample volume
tances and devices; alternatively, remove them from the
shall be of sufficient dimensions and volume to allow mixing,
immediate vicinity of the extraction apparatus.
as described in 7.4.(Warning—The results of the round robin
8.2 Potentiometric Titration Equipment:
have shown that for reliable results, strict adherence to the
8.2.1 Glass Electrode—Before each titration (or each series
sampling and mixing procedure is of the utmost importance.)
of titrations), rinse the electrode with water and soak it for at
7.2 Laboratory Sample—The sample of crude oil presented
least 10 min in 0.1 mol/L hydrochloric acid (see 6.6). Then
tothelaboratoryortestfacilityforanalysisbythistestmethod.
rinse again with water. After titrations store the electrode
Only representative samples obtained as specified in Practices
immersed in reagent water.
D4057 and D4177 shall be used for this test method.
8.2.2 Silver Electrode—Polish the silver electrode before
7.3 Test Sample—The sample aliquot obtained from the
each set of titrations with polishing paper (see 6.13) until a
laboratory sample for analysis by this test method. Once
clean, polished metal surface is obtained.
drawn, the entire portion of the test sample will be used in the
9. Procedure
analysis. Mix the laboratory sample properly, as described in
7.4, prior to drawing the test sample. 9.1 Extraction:
7.4 Homogenize the laboratory sample of crude oil imme- 9.1.1 Weigh about 40 g of sample, to the nearest 0.1 g, into
diately (within 15 min) before drawing the test sample to a 250 mL beaker and heat on a water bath or in an oven to 65
ensure complete homogeneity. Mix the sample at room tem- 6 5°C. Heat 40 6 1 mLof xylene to the same temperature and
perature (15 to 25°C), or less, in the laboratory sample add slowly to the sample while stirring constantly until
container, and record the temperature of the sample in degrees dissolution is complete. Transfer the solution quantitatively to
D6470–99 (2004)
the extraction apparatus, rinsing the beaker with two separate plotting the meter readings versus the volumes of standard
portions of 15 6 1 mLof hot xylene and adding these rinsings silver nitrate solution used in the titration.
also to the extraction apparatus.
NOTE 4—Ifsilverhalidesareprecipitatedonthesilverelectrode,tapthe
9.1.2 While the solution is still hot, add 25 61mLof
electrode gently to dislodge the clinging precipitate and ensure that an
ethanol or isopropyl alcohol and 15 6 1 mL of acetone, using
equilibrium has been reached before taking a meter reading.
these portions for further rinsing of the beaker. Switch on the
9.3.3.2 When using an automatic recording titrator, titrate
heating element of the extraction apparatus to full heat until
with standard silver nitrate solution, adding fixed increments.
boiling begins, then adjust the rheostat to regulate the heat to
NOTE 5—Itisessentialthatincrementaltitrationisapplied,asdescribed
maintain boiling at a vigorous rate, but not at such a rate to
in 9.3.3, to ensure that complete precipitation occurs between additions.
cause bumping in the flask or to cause the condenser to flood.
Allow to reflux for 2 min after the liquid starts boiling (see
9.3.3.3 After each titration, clean the electrodes with water
8.1). Switch off the heater. When boiling ceases, add 125 6 1
(see also 8.2)
mLofwaterandagainbringtheliquidtotheboilandrefluxfor
9.4 Curve Interpretation:
a further 15 min.
9.4.1 The endpoint of the titration is found as the most
9.1.3 Switch off the heater, and allow the two phases to positive value of the steepest portion of the observed inflection
separate for 5 to 10 min. Draw off the aqueous phase, filtering of the titration curve.
through a filter paper into a conical flask of suitable capacity, 9.4.2 The exact location of the inflection point is dependent
stopper the flask, and retain the contents for the total halide onthechlorideconcentration,theelectrodesused,thenatureof
determination as described in 9.2 and 9.3. the titration medium, and the concentration of the silver nitrate
solution applied. To establish the value of the cell potential
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.