ASTM D938-12 (2017) PDF

Full title and description

Standard Test Method for Congealing Point of Petroleum Waxes, Including Petrolatum — ASTM D938 − 12 (Reapproved 2017). This test method defines the procedure for determining the congealing point (the temperature at which a wax sample being cooled develops a resistance to flow) by coating a thermometer bulb with molten wax, allowing it to cool while rotating, and observing the temperature at which the drop ceases to flow.

Abstract

ASTM D938-12 (reapproved 2017) specifies an apparatus-and-observation method to measure the congealing point of petroleum waxes and petrolatums. A wax droplet is adhered to a thermometer bulb, the assembly is cooled at a controlled rate in an air jacket (or equivalent), and the congealing point is recorded as the temperature at which the droplet no longer flows while the thermometer is rotated. The procedure is offered as an alternative to melting-point methods (for example D127) and typically produces lower values than some melting-point procedures. The method includes instrument, sample-handling, and safety guidance (including a mercury warning where applicable).

General information

• Status: Published — D938 − 12 (Reapproved 2017); historically active and listed in ASTM records (later editions of D938 were published after 2017).
• Publication date: Current edition approved June 1, 2017 (published 2017; original designation D938‑12).
• Publisher: ASTM International (formerly American Society for Testing and Materials).
• ICS / categories: 75.140 — Waxes, bituminous materials and other petroleum products.
• Edition / version: Designation D938 − 12 (Reapproved 2017). (Referenced as D938-12R17 or D0938-12R17 in some catalogs.)
• Number of pages: 3 pages (concise test method).

Scope

This test method covers determination of the congealing point of petroleum waxes, including petrolatum. Values are stated in SI units (values in parentheses are for information only). The standard provides warnings about hazardous materials (notably mercury-containing thermometers) and does not claim to address all safety concerns; users must apply appropriate safety and regulatory controls. D938 is described as an alternative to Test Method D127, with results that are often lower than D127 results depending on wax composition.

Key topics and requirements

• Definition of congealing point as the temperature where the cooled wax sample develops a set or resistance to flow.
• Apparatus and materials: thermometer (liquid-in-glass or equivalent), prewarmed flask/air jacket, means to form and observe a wax droplet on the bulb, and calibrated timing/rotation controls.
• Procedure summary: melt sample, coat thermometer bulb, withdraw and cool in air while rotating the thermometer at a controlled rate, observe and record the temperature at which the drop no longer flows.
• Units and reporting: SI units are primary; provide the observed congealing point temperature and any relevant test conditions.
• Safety considerations: warning about mercury thermometers and other hazards; users must follow local regulations and SDS guidance.
• Comparability note: results may differ from other wax melting/congealing tests (e.g., D127); interpret results within the context of the selected test method.

Typical use and users

Used by laboratories, wax and petrolatum manufacturers, quality control and R&D groups in the petrochemical, cosmetics, food-contact coating, candle, adhesive, and packaging industries. Typical users run this test to specify product melting/congealing behaviour, assess formulation consistency, confirm batch-to-batch quality, and support material selection for end-use performance. Laboratories performing regulatory or supply-chain testing for wax-based products commonly include D938 as part of a test suite.

Related standards

Commonly referenced and related ASTM standards include: Test Method D127 (Drop Melting Point of Petroleum Wax, including petrolatum) — an alternative melting-point method; Test Method D937 (Cone Penetration of Petrolatum) for penetration properties; D721 (Oil Content of Petroleum Waxes) and ASTM E1 (thermometer specifications). Users often apply D938 alongside these methods to characterize wax physical properties.

Keywords

congealing point, petroleum wax, petrolatum, wax testing, melting point alternative, ASTM D938, wax properties, phase transition temperature, wax quality control.

FAQ

Q: What is this standard?

A: ASTM D938-12 (Reapproved 2017) is a short ASTM test method that specifies how to determine the congealing point of petroleum waxes and petrolatum by observing a wax droplet on a thermometer bulb as it cools and ceases to flow.

Q: What does it cover?

A: It covers the apparatus, sample preparation, test procedure, observation technique, reporting, and safety considerations (including a mercury warning where applicable) for measuring congealing point. It is intended as an alternative method to some melting-point tests and produces the congealing temperature under defined conditions.

Q: Who typically uses it?

A: Quality-control and R&D laboratories in wax, lubricant, cosmetics, adhesive, candle, and related industries; testing laboratories that characterize petroleum wax and petrolatum products for specification, compliance, and formulation work.

Q: Is it current or superseded?

A: D938‑12 was reapproved in 2017 (commonly cited as D938‑12R17). Subsequent editions of D938 have been published by ASTM (for example, a D938‑25 listing appears in later ASTM catalogs), so users who need the most current procedure should check the latest ASTM designation and edition before use. The D938‑12 (2017) text remains a valid historical/reapproved edition but may have been updated or superseded by later editions.

Q: Is it part of a series?

A: It is part of ASTM Committee D02 (Petroleum Products, Liquid Fuels, and Lubricants) test methods related to petroleum waxes (subcommittee D02.10) and is commonly used in conjunction with related ASTM wax and petrolatum test methods (e.g., D127, D937, D721).

Q: What are the key keywords?

A: Congealing point; petroleum wax; petrolatum; wax testing; ASTM D938; phase transition; quality control; melting point alternative.