ASTM D6470-99(2010)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6470 − 99(Reapproved 2010)
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 Method for Water in Crude Oils by Coulometric
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 ChemicalAnalysis
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 forWater in Crude Oils by Potentiomet-
Nichrome wire.
ric 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 Lubricantsand is the direct responsibility of Subcommittee
D02.03 on Elemental Analysis.
mounted in front of the extraction apparatus (see 5.1).
Current edition approved May 1, 2010. Published May 2010. Originally
5.3 Sampling Tube, glass, length approximately 600 mm,
approved in 1999. Last previous edition approved in 2004 as D6470–99 (2004).
DOI: 10.1520/D6470-99R10.
I.D. approximately 5 mm, with a bulb having a volume of 100
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
mL, or more, and drawn out at one end to an opening of inside
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
diameter (I.D.) 2 to 3 mm. A pipette with cut-off tip makes a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. suitable sample tube.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6470 − 99 (2010)
NOTE 1—Hopkins-type condenser is used.
FIG. 1 Extraction Apparatus
5.4 Potentiometric Titration Equipment, with a measuring 6.1 Purity of Reagents—Unless otherwise indicated, it is
accuracyof 62mV,orbetter,providedwithasilverindicating 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).
6.2 Purity of Water—For all purposes where water is men-
5.5 Magnetic Stirrer, with polytetrafluoroethylene (PTFE)-
tioned, reagent water of a suitable purity shall be used.Various
coated stirring bar.
types of reagent water are described in Specification D1193.
5.6 Homogenizer. A mixer with counter-rotating blades
6.3 Acetone (2-propanone) , conforming to Specification
operatingatapproximately3000r/min(50/s)isusuallysuitable
D329.(Warning—Extremely flammable. Vapors may cause
for homogenization of samples up to 500 mL. Other designs
flashfire.)
can also be used provided the performance conforms to the
requirements described in Annex A1.
5.7 Oven, explosion-proof, temperature 65 6 5°C.
Reagent Chemicals, American Chemical Society Specifications, American
5.8 Filter Paper, Whatman No. 41, or equivalent. Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
listed by the American Chemical Society, see Annual Standards for Laboratory
5.9 Stopwatch.
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
6. Reagents and Materials MD.
D6470 − 99 (2010)
6.4 Alcohol, for example, 95 % (V/V) ethanol, or propan- analysis. Mix the laboratory sample properly, as described in
2–ol (isopropyl alcohol), conforming to Specification D770. 7.4, prior to drawing the test sample.
(Warning—Flammable.)
7.4 Homogenize the laboratory sample of crude oil imme-
6.5 Barium Nitrate, A.R., crystals. (Warning—Barium
diately (within 15 min) before drawing the test sample to
compounds and their solutions present a health risk if incor-
ensure complete homogeneity. Mix the sample at room tem-
rectly handled. Prevent all contact.)
perature (15 to 25°C), or less, in the laboratory sample
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.concentratedhydrochloricacid(density1.19g/mL)to1L
at room temperature, to 3°C above their pour point in order to
with water. (Warning—Corrosive. Causes skin burns.)
facilitate test sample withdrawal. Select the type of mixer
6.7 Nitric Acid, 5 mol/L, aqueous. Cautiously add 325 mL
related to the quantity of crude oil in the laboratory sample
of A.R. concentrated nitric acid (density 1.42 g/mL) to 1 L
container. Before any unknown mixer is used, the specifica-
water, while stirring. (Warning—Corrosive. Causes skin
tions for the homogenization test (see AnnexA1) shall be met.
burns.)
Reevaluate the mixer for any changes in the type of crude, the
6.8 Silver Nitrate Solution, standard, c(AgNO ) = 0.1
quantity of crude, the shape of the sample container, or the
mol/L, aqueous. Prepare, standardize and store as described in mixing conditions (such as mixing speed and time of mixing).
Practice E200 for 0.1 N aqueous solution, reading concentra-
7.5 For small laboratory sample containers and volumes, 50
tions in mol/L in place of normality. Restandardize regularly,
to500mL,anonaerating,highspeed(3000r/min),shearmixer
but in any case before preparation of the standard 0.01 mol/L
is required. Use the mixing time, mixing speed, and height
solution (see 6.9)
above the bottom of the container found to be satisfactory to
NOTE 1—Alternatively, ampoules containing concentrated solutions for
Annex A1. For larger containers and volumes, appropriate
preparation of standard volumetric solutions are available from various
mixing conditions shall be defined by following a set of
suppliers. (Warning—Silver compounds and their solutions present a
procedures similar to those outlined in AnnexA1 and Practice
health risk if incorrectly handled. Prevent all contact.)
D4177 but modified for application to the larger containers and
6.9 Silver Nitrate Solution, standard, c(AgNO ) = 0.01
volumes. Clean and dry the mixer between samples.
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. Dissolve 59 6 1 mg sodium chloride in 1 L water.
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
6.12 Lead Acetate Paper.
possible. Clean and dry the sample tube before and after
sampling.
6.13 Polishing Paper, 800 grit, or finer, to polish the silver
electrode.
8. Preparation of Apparatus
7. Sampling and Sample Preparation
8.1 Extraction Apparatus—To reduce the risk of superheat-
7.1 Sampling is defined as all the steps required to obtain an ing and the resulting hazards, introduce a gentle stream of air
aliquotrepresentativeofthecontentsofanypipe,tank,orother
intothebottomoftheextractionapparatus.Thiscanbedoneby
system, and to place the sample into the laboratory sample passing a length of hypodermic tubing through the bore of the
container.The laboratory sample container and sample volume
tap so that the lower end reaches the bottom of the heating
shall be of sufficient dimensions and volume to allow mixing, tube, while the upper end of the tubing is passed through a
as described in 7.4.(Warning—The results of the round robin
rubber bung in the top of the thistle tube. Place the extraction
have shown that for reliable results, strict adherence to the apparatus behind a safety screen. Shield all electrical resis-
sampling and mixing procedure is of the utmost importance.)
tances and devices; alternatively, remove them from the
immediate vicinity of the extraction apparatus.
7.2 Laboratory Sample—The sample of crude oil presented
tothelaboratoryortestfacilityforanalysisbythistestmethod.
8.2 Potentiometric Titration Equipment:
Only representative samples obtained as specified in Practices
8.2.1 Glass Electrode—Before each titration (or each series
D4057 and D4177 shall be used for this test method.
of titrations), rinse the electrode with water and soak it for at
7.3 Test Sample—The sample aliquot obtained from the least 10 min in 0.1 mol/L hydrochloric acid (see 6.6). Then
rinse again with water. After titrations store the electrode
laboratory sample for analysis by this test method. Once
drawn, the entire portion of the test sample will be used in the immersed in reagent water.
D6470 − 99 (2010)
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
9.1 Extraction: beenestablishedandrecordtheburetteandmeterreadings(see
9.1.1 Weigh about 40 g of sample, to the nearest 0.1 g, into Note 4). In regions between inflections where the potential
a 250 mL beaker and heat on a water bath or in an oven to 65 change is small for each increment of silver nitrate used, add
6 5°C. Heat 40 6 1 mLof xylene to the same temperature and volumes as large as 0.5 mL. When the rate of change of
add slowly to the sample while stirring constantly until potential becomes greater than 5 mV per 0.1 mL, use 0.1 mL
dissolution is complete. Transfer the solution quantitatively to increments of silver nitrate solution. Construct a graph by
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.
NOTE4—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
maintain boiling at a vigorous rate, but not at such a rate to
NOTE5—Itisessentialthatincrementaltitrationisapplied,asdescribed
cause bumping in the flask or to cause the condenser to flood. in 9.3.3, to ensure that complete precipitation occurs between additions.
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
a further 15 min. 9.4 Curve Interpretation:
9.1.3 Switch off the heater, and allow the two phases to
9.4.1
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