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TitleASTM-D2500-Cloud-Point-of-Petroleum-Products-pdf.pdf
TagsBiodiesel Diesel Fuel Ethanol Thermometer Methanol
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Table of Contents
                            Scope
Referenced Documents
Terminology
Summary of Test Method
Significance and Use
Reagents and Materials
FIG. 1
Procedure
Report
Precision and Bias
TABLE 1
Keywords
                        
Document Text Contents
Page 1

Designation: D 2500 – 05

Designation: 219/82

An American National Standard
British Standard 4458

Standard Test Method for
Cloud Point of Petroleum Products1

This standard is issued under the fixed designation D 2500; 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.

1. Scope*

1.1 This test method covers only petroleum products and
biodiesel fuels that are transparent in layers 40 mm in
thickness, and with a cloud point below 49°C.

NOTE 1—The interlaboratory program consisted of petroleum products
of Test Method D 1500 color of 3.5 and lower. The precisions stated in this
test method may not apply to samples with ASTM color higher than 3.5.

1.2 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 appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For specific hazard
statements, see Section 7.

2. Referenced Documents

2.1 ASTM Standards: 2

D 1500 Test Method for ASTM Color of Petroleum Prod-
ucts (ASTM Color Scale)

E 1 Specification for ASTM Liquid-in-Glass Thermometers
2.2 Energy Institute Standard:
Specifications for IP Standard Thermometers 3

3. Terminology

3.1 Definitions of Terms Specific to This Standard:
3.1.1 biodiesel, n—a fuel comprised of mono-alkyl esters of

long chain fatty acids derived from vegetable oils or animal
fats, designated B100.

3.1.1.1 Discussion—Biodiesel is typically produced by a
reaction of vegetable oil or animal fat with an alcohol such as

methanol or ethanol in the presence of a catalyst to yield
mono-esters and glycerin. The fuel typically may contain up to
14 different types of fatty acids that are chemically transformed
into fatty acid methyl esters (FAME).

3.1.2 biodiesel blend, n—a blend of biodiesel fuel with
petroleum-based diesel fuel designated BXX, where XX is the
volume % of biodiesel.

3.1.3 cloud point, n—in petroleum products and biodiesel
fuels, the temperature of a liquid specimen when the smallest
observable cluster of hydrocarbon crystals first occurs upon
cooling under prescribed conditions.

3.1.3.1 Discussion—To many observers, the cluster of wax
crystals looks like a patch of whitish or milky cloud, hence the
name of the test method. The cloud appears when the tempera-
ture of the specimen is low enough to cause wax crystals to
form. For many specimens, the crystals first form at the lower
circumferential wall of the test jar where the temperature is
lowest. The size and position of the cloud or cluster at the cloud
point varies depending on the nature of the specimen. Some
samples will form large, easily observable, clusters, while
others are barely perceptible.

3.1.3.2 Discussion—Upon cooling to temperatures lower
than the cloud point, clusters of crystals will grow in multiple
directions; for example, around the lower circumference of the
test jar, towards the center of the jar, or vertically upwards. The
crystals can develop into a ring of cloud along the bottom
circumference, followed by extensive crystallization across the
bottom of the test jar as temperature decreases. Nevertheless,
the cloud point is defined as the temperature at which the
crystals first appear, not when an entire ring or full layer of wax
has been formed at the bottom of the test jar.

3.1.3.3 Discussion—In general, it is easier to detect the
cloud point of samples with large clusters that form quickly,
such as paraffinic samples. The contrast between the opacity of
the cluster and the liquid is also sharper. In addition, small
brightly-reflective spots can sometimes be observed inside the
cluster when the specimen is well illuminated. For other more
difficult samples, such as naphthenic, hydrocracked, and those
samples whose cold flow behavior have been chemically
altered, the appearance of the first cloud can be less distinct.
The rate of crystal growth is slow, the opacity contrast is weak,

1 This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.07 on Flow Properties.

Current edition approved July 1, 2005. Published August 2005. Originally
approved in 1966. Last previous edition approved in 2002 as D 2500–02e1.

2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [email protected] For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.

3 Available from Energy Institute, 61 New Cavendish St., London, England WIM
8AR.

1

*A Summary of Changes section appears at the end of this standard.

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Page 2

and the boundary of the cluster is more diffuse. As the
temperature of these specimens decrease below the cloud
point, the diffuse cluster will increase in size and can form a
general haze throughout. A slight haze throughout the entire
sample, which slowly becomes more apparent as the tempera-
ture of the specimen decreases, can also be caused by traces of
water in the specimen instead of crystal formation (see Note 4).
With these difficult samples, drying the sample prior to testing
can eliminate this type of interference.

3.1.3.4 Discussion—The purpose of the cloud point method
is to detect the presence of the wax crystals in the specimen;
however trace amounts of water and inorganic compounds may
also be present. The intent of the cloud point method is to
capture the temperature at which the liquids in the specimen
begin to change from a single liquid phase to a two-phase
system containing solid and liquid. It is not the intent of this
test method to monitor the phase transition of the trace
components, such as water.

4. Summary of Test Method

4.1 The specimen is cooled at a specified rate and examined
periodically. The temperature at which a cloud is first observed
at the bottom of the test jar is recorded as the cloud point.

5. Significance and Use

5.1 For petroleum products and biodiesel fuels, cloud point
of a petroleum product is an index of the lowest temperature of
their utility for certain applications.

6. Apparatus (see Fig. 1)

6.1 Test Jar, clear, cylindrical glass, flat bottom, 33.2 to
34.8-mm outside diameter and 115 and 125-mm height. The
inside diameter of the jar may range from 30 to 32.4 mm within
the constraint that the wall thickness be no greater than 1.6
mm. The jar should be marked with a line to indicate sample
height 54 6 3 mm above the inside bottom.

6.2 Thermometers, having ranges shown below and con-
forming to the requirements as prescribed in Specification E 1
or Specifications for IP Standard Thermometers.

Thermometer
Number

Thermometer Temperature Range ASTM IP
High cloud and pour −38 to +50°C 5C 1C
Low cloud and pour −80 to +20°C 6C 2C

6.3 Cork, to fit the test jar, bored centrally for the test
thermometer.

6.4 Jacket, metal or glass, watertight, cylindrical, flat bot-
tom, about 115 mm in depth, with an inside diameter of 44.2 to
45.8 mm. It shall be supported free of excessive vibration and
firmly in a vertical position in the cooling bath of 6.7 so that
not more than 25 mm projects out of the cooling medium.

6.5 Disk, cork or felt, 6-mm thick to fit loosely inside the
jacket.

6.6 Gasket, ring form, about 5 mm in thickness, to fit snugly
around the outside of the test jar and loosely inside the jacket.
The gasket may be made of rubber, leather, or other material
that is elastic enough to cling to the test jar and hard enough to
hold its shape. Its purpose is to prevent the test jar from
touching the jacket.

6.7 Bath or Baths, maintained at prescribed temperatures
with a firm support to hold the jacket vertical. The required
bath temperatures may be maintained by refrigeration if
available, otherwise by suitable freezing mixtures.

NOTE 2—The mixtures commonly used for temperatures down to those
shown are as follows:

Ice and water 10°C
Crushed ice and sodium chloride crystals −12°C
Crushed ice and calcium chloride crystals −26°C
Acetone, methyl or ethyl alcohol, or petroleum naphtha

chilled in a covered metal beaker with an ice-salt mix-
ture to −12°C, then with enough solid carbon dioxide to
give the desired temperature

−57°C

7. Reagents and Materials

7.1 Acetone—Technical grade acetone is suitable for the
cooling bath, provided it does not leave a residue on drying.
(Warning—Extremely flammable.)

7.2 Calcium Chloride—Commercial or technical grade cal-
cium chloride is suitable.

7.3 Carbon Dioxide (Solid) or Dry Ice—A commercial
grade of dry ice is suitable for use in the cooling bath.

7.4 Ethanol or Ethyl Alcohol—A commercial or technical
grade of dry ethanol is suitable for the cooling bath.
(Warning—Flammable. Denatured, cannot be made non-
toxic.)

7.5 Methanol or Methyl Alcohol—A commercial or techni-
cal grade of dry methanol is suitable for the cooling bath.
(Warning—Flammable. Vapor harmful.)

7.6 Petroleum Naphtha—A commercial or technical grade
of petroleum naphtha is suitable for the cooling bath.
(Warning—Combustible. Vapor harmful.)

7.7 Sodium Chloride Crystals—Commercial or technical
grade sodium chloride is suitable.

7.8 Sodium Sulfate—A reagent grade of anhydrous sodium
sulfate should be used when required (see Note 4).

NOTE—All dimensions are in milllimetres.
FIG. 1 Apparatus for Cloud Point Test

D 2500 – 05

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Page 3

8. Procedure

8.1 Bring the sample to be tested to a temperature at least
14°C above the expected cloud point. Remove any moisture
present by a method such as filtration through dry lintless filter
paper until the oil is perfectly clear, but make such filtration at
a temperature of at least 14°C above the approximate cloud
point.

8.2 Pour the sample into the test jar to the level mark.
8.3 Close the test jar tightly by the cork carrying the test

thermometer. Use the high cloud and pour thermometer if the
expected cloud point is above −36°C and the low cloud and
pour thermometer if the expected cloud point is below −36°C.
Adjust the position of the cork and the thermometer so that the
cork fits tightly, the thermometer and the jar are coaxial, and
the thermometer bulb is resting on the bottom of the jar.

NOTE 3—Liquid column separation of thermometers occasionally oc-
curs and may escape detection. Thermometers should be checked periodi-
cally and used only if their ice points are 0 6 1°C, when the thermometer
is immersed to the immersion line in an ice bath, and when the emergent
column temperature does not differ significantly from 21°C. Alternatively,
immerse the thermometer to a reading and correct for the resultant cooler
stem temperature.

8.4 See that the disk, gasket, and the inside of the jacket are
clean and dry. Place the disk in the bottom of the jacket. The
disk and jacket shall have been placed in the cooling medium
a minimum of 10 min before the test jar is inserted. The use of
a jacket cover while the empty jacket is cooling is permitted.
Place the gasket around the test jar, 25 mm from the bottom.
Insert the test jar in the jacket. Never place a jar directly into
the cooling medium.

NOTE 4—Failure to keep the disk, gasket, and the inside of the jacket
clean and dry may lead to frost formation, which may cause erroneous
results.

8.5 Maintain the temperature of the cooling bath at 0 6
1.5°C.

8.6 At each test thermometer reading that is a multiple of
1°C, remove the test jar from the jacket quickly but without
disturbing the specimen, inspect for cloud, and replace in the
jacket. This complete operation shall require not more than 3 s.
If the oil does not show a cloud when it has been cooled to 9°C,
transfer the test jar to a jacket in a second bath maintained at
a temperature of −18 6 1.5°C (see Table 1). Do not transfer the
jacket. If the specimen does not show a cloud when it has been
cooled to −6°C, transfer the test jar to a jacket in a third bath
maintained at a temperature of −336 1.5°C. For the determi-
nation of very low cloud points, additional baths are required,
each bath to be maintained in accordance with Table 1. In each
case, transfer the jar to the next bath, if the specimen does not
exhibit cloud point and the temperature of the specimen

reaches the lowest specimen temperature in the range identified
for the current bath in use, based on the ranges stated in Table
1.

8.7 Report the cloud point, to the nearest 1°C, at which any
cloud is observed at the bottom of the test jar, which is
confirmed by continued cooling.

NOTE 5—A wax cloud or haze is always noted first at the bottom of the
test jar where the temperature is lowest. A slight haze throughout the entire
sample, which slowly becomes more apparent as the temperature is
lowered, is usually due to traces of water in the oil. Generally this water
haze will not interfere with the determination of the wax cloud point. In
most cases of interference, filtration through dry lintless filter papers, such
as described in 8.1, is sufficient. In the case of diesel fuels, however, if the
haze is very dense, a fresh portion of the sample should be dried by
shaking 100 mL with 5 g of anhydrous sodium sulfate for at least 5 min
and then filtering through dry lintless filter paper. Given sufficient contact
time, this procedure will remove or sufficiently reduce the water haze so
that the wax cloud can be readily discerned. Drying and filtering should be
done always at a temperature at least 14°C above the approximate cloud
point but otherwise not in excess of 49°C.

9. Report

9.1 Report the temperature recorded in 8.7 as the cloud
point, Test Method D 2500.

10. Precision and Bias

10.1 The precision of this test method as determined by
statistical examination of interlaboratory results is as follows:

10.1.1 Repeatability—The difference between two test re-
sults, 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
this test method, exceed 2°C only in 1 case in 20.

10.1.2 Reproducibility—The difference between two single
and independent results obtained by different operators work-
ing in different laboratories on identical test material, would in
the long run, in the normal and correct operation of this test
method, exceed 4°C only in 1 case in 20.

10.1.3 The precision statements were derived from a 1990
interlaboratory cooperative test program.4 Participants ana-
lyzed 13 sample sets comprised of various distillate fuels and
lubricating oils with temperature range from -1 to -37°C. Eight
laboratories participated with the manual D 2500/IP219 test
method. Information on the type of samples and their average
cloud points are in the research report.

10.2 Bias—The procedure in this test method has no bias,
because the value of cloud point can be defined only in terms
of a test method.

10.3 Precision for Biodiesel Products5—The precision of
this test method as determined by statistical examination of
interlaboratory results is as follows:

10.3.1 Repeatability for Blends of Biodiesel in Diesel—The
difference between successive test results obtained by the same
operator, using the same apparatus, under constant operating

4 Supporting data have been filed at ASTM International Headquarters and may
be obtained by requesting Research Report RR: D02–1444.

5 Supporting data (the results of the 2001 interlaboratory cooperative test
program) have been filed at ASTM International Headquarters and may be obtained
by requesting Research Report RR: D02–1524.

TABLE 1 Bath and Sample Temperature Ranges

Bath Bath Temperature Setting, °C
Sample Temperature Range,

°C

1 0 6 1.5 Start to 9
2 −18 6 1.5 9 to −6
3 –33 6 1.5 −6 to −24
4 −51 6 1.5 −24 to −42
5 −69 6 1.5 −42 to −60

D 2500 – 05

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