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D255-92 – Standard Test Method Technical Guide
📐 Apparatus and Specifications
The ASTM D255-92 standard specifies the use of a steam generator with a capacity of approximately 2 gallons (7600 cm³), made of metal or glass. A metal bath is required to immerse the distilling flask to at least 4 inches (101.6 mm). The distilling flask is a 1000-cm³ heat-resistant glass flask with a ring neck. The flask is fitted with a three-hole rubber stopper for the steam delivery tube, vapor outlet tube, and thermometer.
| 🟦 Component | 📏 Specification |
|---|---|
| Steam Generator | 2 gal (7600 cm³) capacity |
| Distilling Flask | 1000 cm³, heat-resistant glass |
| Bath Immersion Depth | 4 in (101.6 mm) minimum |
| Thermometer | ASTM Low Distillation, -2 to +300°C |
Tip: The thermometer must conform to Specification E 1 for accuracy.
⚙️ Test Procedure and Safety Considerations
The procedure involves steam distillation to separate solvent and base. The steam generator should have pinch-cocks or valves to control flow. Safety is emphasized; users must establish appropriate safety practices. The standard does not address all hazards, so regulatory limitations should be considered.
An electric mantle heater with a variable resistance transformer can replace the bath and heat source. The condenser dimensions are critical for efficient operation.
Warning: Always follow safety protocols when handling bituminous materials and high-temperature equipment.
📊 Key Dimensional Requirements
The condenser and adapter have specific dimensions to ensure proper condensation and collection.
| 🔧 Component | 📐 Dimension |
|---|---|
| Condenser Jacket Length | 250 ± 5 mm |
| Condenser Tube Length | 400 ± 25 mm |
| Tube Outside Diameter | 12.5 ± 0.5 mm |
| Expanded End Diameter | 23 ± 1 mm |
| Expanded End Length | 75 ± 1 mm |
| Adapter Angle | Approximately 105° |
Tip: Ensure the adapter outlet is cut at a 45° angle for efficient drainage.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D255-92?
The standard describes a method for steam distillation of bituminous protective coatings to separate and recover solvent and base.
💡 What thermometer is required for this method?
An ASTM Low Distillation thermometer with a range of -2 to +300°C, as specified in Specification E 1.
⚡ What are the safety hazards associated with this test?
The standard does not address all safety concerns. Users must establish appropriate safety and health practices and comply with regulatory limitations.
📌 What are the key dimensions of the distilling flask setup?
The distilling flask has a capacity of 1000 cm³, and the steam delivery tube must reach within 3/8 ± 1/8 inch (9.5 ± 4.7 mm) of the bottom.