ASTM D721-17

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
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: D721 − 15 D721 − 17
Designation: 158/69(85)
Standard Test Method for
Oil Content of Petroleum Waxes
This standard is issued under the fixed designation D721; 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 oil in petroleum waxes having a congealing point of 30 °C (86 °F) or higher
as determined in accordance with Test Method D938, and containing not more than 15 % of oil.
NOTE 1—With some types of waxes, of oil contents greater than 5 %, there may be an incompatibility with MEK resulting in the formation of two
liquid phases. If this occurs, the test method is not applicable to the material under test.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.3 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.
1.4 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
E1 Specification for ASTM Liquid-in-Glass Thermometers
E128 Test Method for Maximum Pore Diameter and Permeability of Rigid Porous Filters for Laboratory Use
E2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
2.2 Energy Institute Standards:
Specification for IP Standard Thermometers
3. Summary of Test Method
3.1 The sample is dissolved in methyl ethyl ketone, the solution cooled to –32 °C (–25 °F) to precipitate the wax, and filtered.
The oil content of the filtrate is determined by evaporating the methyl ethyl ketone and weighing the residue.
4. Significance and Use
4.1 The oil content of a wax may have significant effects on several of its properties, such as strength, hardness, flexibility, scuff
resistance, coefficient of friction, coefficient of expansion, melting point, and oil straining. The importance of these effects may be
dependent upon the ultimate use of the wax.
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
D02.10.0A on Physical/Chemical Properties.
Current edition approved June 1, 2015May 1, 2017. Published June 2015June 2017. Originally approved in 1943. Last previous edition approved in 20112015 as D721 – 06
(2011).D721 – 15. DOI: 10.1520/D0721-15.10.1520/D0721-17.
In the IP, this test method is under the jurisdiction of the Standardization Committee. This test method was issued as a joint ASTM-IP tentative in 1964.
This test method was prepared jointly by the Technical Association of Pulp and Paper Industry and ASTM International.
This test method has been adopted for use by government agencies to replace Method 5431 of Federal Test Method Standard No. 79lb.
This test method is being used by some laboratories for products of higher oil content.
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.
Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR, U.K.
*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
D721 − 17
All dimensions are in millimetres
FIG. 1 Filter Stick
5. Apparatus
5.1 Filter Stick and Assembly, consisting of a 10 mm diameter sintered glass filter stick of 10 μm to 15 μm maximum pore
diameter as determined by the method in Appendix X1, provided with an air pressure inlet tube and delivery nozzle. It is provided
with a ground-glass joint to fit a 25 mm by 170 mm test tube. The dimensions for a suitable filtration assembly are shown in Fig.
1.
NOTE 2—A metallic filter stick may be employed if desired. A filter stick made of stainless steel and having a 12.7 mm ( ⁄2 in.) disk of 10 μm to 15 μm
maximum pore diameter, as determined by Test Method E128, has been found to be satisfactory. The metallic apparatus is inserted into a 25 mm by
150 mm test tube and held in place by means of a cork.
5.2 Cooling Bath, consisting of an insulated box with 30 mm 6 5 mm (1.2 in. 6 0.2 in.) holes in the center to accommodate
any desired number of test tubes. The bath may be filled with a suitable medium such as kerosine, and may be cooled by circulating
a refrigerant through coils, or by using solid carbon dioxide. A suitable cooling bath to accommodate three test tubes is shown in
Fig. 2.
5.3 Pipet, or equivalent dispensing device capable of delivering 1 g 6 0.05 g of molten wax.
5.4 Transfer Pipet, or equivalent volume dispensing device, capable of delivering 15 mL 6 0.06 mL.
5.5 Air Pressure Regulator, designed to supply air to the filtration assembly (8.5) at the volume and pressure required to give
an even flow of filtrate. Either the conventional pressure-reducing valve or a mercury bubbler-type regulator has been found
satisfactory. The latter type, illustrated in Fig. 3, consists of a 250 mL glass cylinder and a T-tube held in the cylinder by means
of a rubber stopper grooved at the sides to permit the escape of excess air. The volume and pressure of the air supplied to the
filtration assembly is regulated by the depth to which the T-tube is immersed in mercury at the bottom of the cylinder. Absorbent
cotton placed in the space above the mercury prevents the loss of mercury by spattering. The air pressure regulatory is connected
to the filter stick and assembly by means of rubber tubing.
5.6 Temperature Measuring Temperature-Measuring Device:
The sole source of supply of a suitable metal filter stick with designated porosity G known to the committee at this time is the Pall Corporation, 2200 Northern Boulevard
East Hills, NY 11548. A list of United Kingdom suppliers can be obtained from Energy Institute, 61 New Cavendish St., London, W1G 7AR, United Kingdom. If you are
aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the
responsible technical committee, which you may attend.
D721 − 17
All dimensions are in millimetres (inches)
FIG. 2 Cooling Bath
5.6.1 Thermometer, having a range as shown below and conforming to the requirements as prescribed in Specification E1,
Specification E2251, or in the Specification for IP Standard Thermometers.
Thermometer Number
Temperature Range ASTM IP
–38 °C to +50 °C S5C .
–36 °F to +120 °F S5F .
–37 °C to +21 °C 71C 72C
–35 °F to +70 °F 71F 72F
5.6.2 Temperature measuring Temperature-measuring devices other than those described in 5.6.1 are satisfactory for this test
method, provided that they exhibit the same temperature response as the equivalent mercury-in-glass thermometers.
5.7 Weighing Bottles, glass-stoppered, having a typical capacity of 15 mL to 25 mL.
5.8 Evaporation Assembly, consisting of an evaporating cabinet and connections, essentially as illustrated in Fig. 4, and capable
of maintaining a temperature of 35 °C 6 1 °C (95 °F 6 2 °F) around the evaporation flask. Construct the jets with an inside
diameter of 4 mm 6 0.2 mm for delivering a stream of clean, dry air vertically downward into the weighing bottle. Support each
jet so that the tip is 15 mm 6 5 mm above the surface of the liquid at the start of the evaporation. Supply purified air at the rate
of 2 L ⁄min to 3 L ⁄min per jet. One way to purify the air is by passage through a tube of approximately 10-mm10 mm bore packed
D721 − 17
All dimensions are in millimetres
FIG. 3 Air Pressure Regulator
loosely to a height of approximately 200 mm with absorbent cotton. Periodically check the cleanliness of the air by evaporating
4 mL of methyl ethyl ketone by the procedure specified in 8.5. When the residue does not exceed 0.1 mg, the evaporation
equipment is operating satisfactorily.
5.9 Analytical Balance, capable of reproducing weights to 0.1 mg.
5.10 Wire Stirrer—A piece of stiff wire, made of iron, stainless steel, or Nichrome wire of about No. 20 B & S (0.9 mm in
diameter) or 16 swg gage, 250 mm long. A 10 mm diameter loop is formed at each end, and the loop at the bottom end is bent
so that the plane of the loop is perpendicular to the wire.
6. Reagents
6.1 Methyl Ethyl Ketone, conforming to the specifications of the Committee on Analytical Reagents of the American Chemical
Society.
6.2 Store the solvent mixture over a suitable drying agent, such as anhydrous calcium sulfate (five mass percent of the solvent).
Filter prior to use.
6.3 Air Supply, clean and filtered.
NOTE 3—As an alternative, it is permissible to replace all references to “air” with “nitrogen,” provided the nitrogen is clean and filtered. It should be
noted, however, that the precision statements for the test method were determined using air only and that the precision associated with using nitrogen
has not been determined.
7. Sample
7.1 If the sample of wax is 1 kg (2 lb) or less, obtain a representative portion by melting the entire sample and stirring
thoroughly. For samples over 1 kg (2 lb), exercise special care to ensure obtaining a truly representative portion, bearing in mind
that the oil may not be distributed uniformly throughout the sample, and that mechanical operations may express some of the oil.
8. Procedure
8.1 Melt a representative portion of the sample, using a water bath or oven maintained at 70 °C to 100 °C (158 °F to 212 °F).
As soon as the wax is completely melted, thoroughly mix. Preheat the pipet or equivalent measuring device in order to prevent
the solidification of wax in the tip, and withdraw a portion of the sample as soon as possible after the wax has melted. The mass
of wax transferred to the test tube must be 1.00 g 6 0.05 g. Allow the test tube to cool, and weigh to at least the nearest 1 mg.
NOTE 4—The weight of a test tube which is cleaned by means of solvents will not vary to a significant extent. Therefore, a tare weight may be obtained
and used repeatedly.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of
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