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D246-04 – Standard Test Method Technical Guide
ASTM Designation D 246 – 04a, also standardized as AASHTO T 62, establishes a controlled laboratory procedure for the distillation of creosote and creosote-coal tar solutions. This test method is essential for analyzing the boiling range of these wood preservatives, directly impacting their quality and suitability for industrial applications such as the treatment of piles, poles, and timbers.
🧪 Apparatus Configuration and Standards
The accuracy of the distillation test relies on strict adherence to the apparatus specifications defined in the standard and its referenced documents. The primary glassware required is a 300 mL distillation flask conforming to Type II, Class 2 of Specification E 1405. A tapered glass condenser tube is specified with precise dimensional tolerances, and the heat source can be a Bunsen or Meker type gas burner or an electric heater with a variable output up to 600 or 750 W.
| 🟦 Apparatus Component | 📏 Specified Dimension or Type |
|---|---|
| Distillation Flask | 300 mL, Type II, Class 2 (Specification E 1405) |
| Condenser Tube (Overall Length) | 360 ± 4 mm |
| Condenser Tube (Small End OD) | 12.5 ± 1.5 mm |
| Condenser Tube (Large End OD) | 28.5 ± 3.0 mm |
| Length of Tapered Condenser Part | 100 ± 5 mm |
| Wire Gauze for Support | 16-mesh, 0.51 mm Nichrome, 125 to 152 mm diameter |
| ⚡ Heat Source & Shield Parameter | 🎯 Specification |
|---|---|
| Electric Heater Power Output | 600 or 750 W |
| Burner Chimney Height (Gas Burner) | Approx. 100 mm |
| Burner Chimney Diameter | 95 to 105 mm |
| Peephole in Chimney Diameter | 25 mm, centered about 32 mm below the ring support |
| Flask Shield Construction | Stainless Steel, Mica Windows, Ceramic Board Lining, Transite Cover |
💡 Tip: The standard specifies a dedicated flask shield for electric heater distillation. While the construction and cover are the same as the flame distillation shield, the overall height is different. Always verify the correct shield dimensions for the selected heat source to ensure proper thermal performance.
📊 Distillation Procedure and Quality Compliance
The test method calls for the distillation of a 100 g sample in the 300 mL flask at a carefully controlled rate. The weights of distillate fractions are collected at a series of specified temperatures, and the weight of the residue is determined at the maximum specified temperature, providing the critical boiling range data required for quality control. Sampling must be conducted in accordance with Test Methods D 38, and Practice D 370 is referenced for sample dehydration if needed.
As stated in Section 4.1, creosote quality is directly defined by the boiling ranges of its distillation fractions. The boiling limits determined by this test method must conform to the limits established by Specifications D 390 (Coal-Tar Creosote) and D 391 (Creosote-Coal Tar Solution) to qualify the preservative as acceptable for its intended application.
✅ Conformance Criteria: The boiling ranges derived from the distillate fractions must strictly adhere to the acceptance limits in Specifications D 390 and D 391. The resulting residue and distillates may also be tested by appropriate procedures when required by the specifier.
⚠️ Safety Note: As stated in Section 1.2, this standard does not purport to address all safety concerns. It is the responsibility of the user to establish appropriate safety, health, and regulatory compliance practices before conducting the test.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D246-04?
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.