ASTM D156-23

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D156 − 15 D156 − 23
Standard Test Method for
Saybolt Color of Petroleum Products (Saybolt Chromometer
Method)
This standard is issued under the fixed designation D156; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method covers the determination of the color of refined oils such as undyed motor and aviation gasoline, jet
propulsion fuels, naphthas and kerosine, and, in addition, petroleum waxes and pharmaceutical white oils.
NOTE 1—For determining the color of petroleum products darker than Saybolt Color − 16, see Test Method D1500.
1.2 This test method reports results specific to this test method and recorded as, “Saybolt Color units.”
1.3 The values stated in inch-pound units or in SI units and which are not in parentheses are to be regarded as the standard. The
values given in parentheses are for information only.
NOTE 2—Oil tubes and apparatus used in this test method have traditionally been marked in inches, (the tube is required to be etched with ⁄8 in. divisions.)
1 1 1
The Saybolt Color Numbers are aligned with inch, ⁄2 in., ⁄4 in., and ⁄8 in. changes in the depth of oil. These fractional inch changes do not readily
correspond to SI equivalents and in view of the preponderance of apparatus already in use and marked in inches, the inch/pound unit is regarded as the
standard. However the test method does use SI units of length when the length is not directly related to divisions on the oil tube and Saybolt Color
Numbers. The test method uses SI units for temperature.
1.4 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
D938 Test Method for Congealing Point of Petroleum Waxes, Including Petrolatum
D1500 Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.
Current edition approved April 1, 2015Oct. 1, 2023. Published April 2015October 2023. Originally approved in 1923. Last previous edition approved in 20122015 as
D156 – 12.D156 – 15. DOI: 10.1520/D0156-15.10.1520/D0156-23.
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 ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D156 − 23
TABLE 1 Saybolt Colors Corresponding to Depths of Oil
Number of Color Number of Color Depth of Oil,
Depth of Oil, in. (mm) Color Number Color Number
Standards Standards in. (mm)
One-half 20.00 (508) +30 Two 6.00 (152) +6
One-half 18.00 (457) +29 Two 5.75 (146) +5
One-half 16.00 (406) +28 Two 5.50 (139) +4
One-half 14.00 (355) +27 Two 5.25 (133) +3
One-half 12.00 (304) +26 Two 5.00 (127) +2
One 20.00 (508) +25 Two 4.75 (120) +1
One 18.00 (457) +24 Two 4.50 (114) 0
One 16.00 (406) +23 Two 4.25 (107) −1
One 14.00 (355) +22 Two 4.00 (101) −2
One 12.00 (304) +21 Two 3.75 (95) −3
One 10.75 (273) +20 Two 3.625 (92) −4
One 9.50 (241) +19 Two 3.50 (88) −5
One 8.25 (209) +18 Two 3.375 (85) −6
One 7.25 (184) +17 Two 3.25 (82) −7
One 6.25 (158) +16 Two 3.125 (79) −8
Two 10.50 (266) +15 Two 3.00 (76) −9
Two 9.75 (247) +14 Two 2.875 (73) −10
Two 9.00 (228) +13 Two 2.75 (69) −11
Two 8.25 (209) +12 Two 2.625 (66) −12
Two 7.75 (196) +11 Two 2.50 (63) −13
Two 7.25 (184) +10 Two 2.375 (60) −14
Two 6.75 (171) +9 Two 2.25 (57) −15
Two 6.50 (165) +8 Two 2.125 (53) −16
Two 6.25 (158) +7
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
E308 Practice for Computing the Colors of Objects by Using the CIE System
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.1.2 clear-and-bright, n—condition in which the sample is free of haze or cloudiness. (Also termed clean-and-bright .)
3.1.3 free water, n—water in excess of that soluble in the sample and appearing in the sample as a haze or cloudiness, as droplets,
or as a separated phase or layer.
3.1.4 particulates, n—small solid or semisolid particles, sometimes referred to as silt or sediment, that can be suspended in the
sample or can settle to the bottom.
3.1.5 turbidity, n—reduction of transparency of a sample due to the presence of particulate matter or water haze, or both.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 Saybolt color, n—an empirical definition of the color of a clear petroleum liquid based on a scale of −16 (darkest) to +30
(lightest).
3.2.1.1 Discussion—
The number is derived by finding the height of a column of the sample that, when viewed through the length of the column, visually
matches the appropriate one of three glass standards and referring to Table 1 of Test Method D156.
4. Summary of Test Method
4.1 The height of a column of sample is decreased by levels corresponding to color numbers until the color of the sample is
unmistakably lighter than that of the standard. The color number above this level is reported, regardless of whether the sample was
darker, questionable, or a match at the higher level.
5. Significance and Use
5.1 Determination of the color of petroleum products is used mainly for manufacturing control purposes and is an important
D156 − 23
quality characteristic since color is readily observed by the user of the product. In some cases the color may serve as an indication
of the degree of refinement of the material. When the color range of a particular product is known, a variation outside the
established range can indicate possible contamination with another product. However, color is not always a reliable guide to
product quality and should not be used indiscriminately in product specifications.
6. Apparatus
6.1 The Saybolt chromometer consisting of sample and standard tubes, optical system, light source, and color standards, is
described in detail in Annex A1 and illustrated in Fig. A1.1.
7. Standardization of Apparatus
7.1 Remove the glass disk from the bottom of the oil tube. Clean the disk, oil tube, and plain tube. When deposits are not
removable by wiping or solvent rinsing, wash with soap and water. After cleaning, rinse with distilled or deionized water and with
acetone or some other suitable solvent, and dry. Assemble the oil tube, and position the tubes in the instrument.
7.2 Using the specified light source and illumination, observe the comparative light intensity of the two halves of the optical field,
with both tubes empty, and with the 12 mm diaphragm removed from under the plain tube. The intensity of light observed in each
half of the optical field must be the same. Adjustment in the position of the light source may be necessary to achieve this match.
NOTE 3—On some instruments, removal of the 12 mm diaphragm can prevent the assembly from seating against the base (about a ⁄4 in. gap), which can
let a lot of stray light in that may affect the light intensity when trying to compare the two halves of the optical field in 7.2. If this occurs, follow the
procedure in 7.3 (where the 12 mm diaphragm has been reattached) as the basis to ensure the light source has been properly set to provide the same light
intensity in both halves of the optical field.
7.3 Replace the 12 mm diaphragm under the plain tube, and fill the oil tube to the 20 in. (508 mm) mark with distilled or deionized
water. The intensity of the light observed in each half of the optical field must be the same, for the instrument to be judged
satisfactory for use. The optical properties of glass, from different batches, can vary significantly and it is recommended that only
matched tubes, such as described in the Appendix, be used in this test. When a tube is broken, replace both tubes with a matched
pair of tubes.
8. Sampling
8.1 Samples shall be taken in accordance with the instructions in Practice D4057.
9. Preparation of Test Specimen
9.1 Samples (Excluding Waxes)—If the sample is contained in a clear, transparent container, such as glass bottle, visually inspect
the sample for evidence of free water, particulate contamination, and haze by holding the container up to the light. If the sample
is contained in a nontransparent container, shake or agitate the sample container vigorously to uniformly suspend any free water
that may be present in the sample before transferring a portion to a clear, transparent container to conduct the visual inspection
before proceeding.
9.2 Wax Samples—Carry out the same procedure in 9.1, except that the sample is to be heated to a temperature just enough to
ensure the sample is liquid (see 9.4). (Warning—Take appropriate safety precautions in handling the sample at elevated
temperatures.)
9.3 When the sample is not clear-and-bright (that is, visual inspection in 9.1 or 9.2 shows any presence of turbidity, free water,
or particulates, or a combination thereof), filter through a sufficient number of qualitative filter papers until it is clear. For wax
samples requiring filtration, it will be necessary to heat the filter paper and apparatus (for example, a filter funnel) that can come
in contact with the molten sample to a temperature sufficient to prevent the sample from solidifying during the filtration process
(see 9.4).
9.4 When preparing petroleum wax for testing do not heat excessively, because oxidation can occur, with consequent discoloration
of the test specimen. A sample heated to a temperature of 8 °C to 17 °C above its congealing point as determined in accordance
with Test Method D938, has been found suitable to test samples using this test method.
D156 − 23
TABLE 2 Example of Procedure
Using One Using Two
Whole Color Whole Color
Observation
Standard, in. Standards,
(mm) in. (mm)
Oil darker at depth of 16 (406) 4.5 (102)
Oil darker at depth of 14 (355) 4.25 (107)
Oil questionable at depth of 12 (304) 4.0 (101)
Oil lighter at depth of 10.75 (273) 3.75 (95)
Saybolt color +21 −2
10. Procedure for Refined Light Oils and Pharmaceutical White Oils
10.1 Flush the oil tube with a portion of the test specimen, taking care to allow the tube to drain thoroughly. Fill the oil tube with
the test specimen compare with a whole color standard. When the test specimen is lighter than the color standard, remove the
standard and replace it with a half standard. When the sample is darker than the single whole standard at 6 ⁄4 in. (158 mm), add
another whole standard. (Warning—It is important that all samples in the color tubes be free from air bubbles.)
10.2 With the proper color standard or standards in place, and the test specimen in the oil tube at a level where its color is
decidedly darker than that of the color standard, draw off
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