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D1108-21 – Standard Test Method Technical Guide
🧪 Overview and Significance
This test method, designated D1108-21, covers the determination of dichloromethane soluble content in wood, which serves as a measure of waxes, fats, resins, oils, and similar materials. The dichloromethane extractable content is influenced by seasoning or drying the wood, and it includes substances such as phytosterols and nonvolatile hydrocarbons. This standard is essential for assessing wood quality in various industrial applications.
⚙️ Apparatus and Test Procedure
The required apparatus includes filtering crucibles (Alundum or fritted-glass, coarse porosity) and a Soxhlet extraction apparatus with ground-glass joints. The Soxhlet extraction flask has a capacity of 250 mL, and the extraction tube has an inside diameter of 45 to 50 mm with a capacity to the top of the siphon of approximately 100 mL and a siphon tube height of approximately 55 mm. A water-cooled condenser is used.
| 🟦 Component | 📏 Specification |
|---|---|
| Extraction Flask | 250 mL capacity |
| Extraction Tube ID | 45–50 mm |
| Tube Capacity to Siphon | ~100 mL |
| Siphon Tube Height | ~55 mm |
The test specimen is 2 g of air-dried sawdust ground to pass a 425-µm (40 mesh) sieve and retained on a 250-µm (60 mesh) sieve. Two specimens are weighed in tared crucibles. One specimen is dried in an oven for 2 h at 100 to 105°C, then cooled and weighed until constant weight to determine the moisture-free proportion. The other specimen is extracted in a fume hood using 150 mL of dichloromethane for 6 to 8 h, with at least six to eight siphonings per hour. A small disk of fine-mesh screen wire is placed in the crucible top to prevent sample loss.
⚠️ Warning: Dichloromethane causes narcosis when inhaled and can be irritating to the eyes. Proper caution must be used, and all steps should be carried out in a fume hood.
After extraction, the solvent is evaporated, preferably using a rotary evaporator. The flask and contents are dried in an oven for 1 h at 100 to 105°C, cooled in a desiccator, and weighed. This is repeated until no further weight loss occurs.
📊 Calculation and Reporting
Results are reported as percentage by weight of dichloromethane soluble matter in moisture-free wood using the formula:
Dichloromethane soluble matter (%) = (W2 / (W1 × P)) × 100
Where:
- W2 = weight of dried extract
- W1 = weight of test specimen used for extraction
- P = proportion of moisture-free sawdust in the air-dry specimen
| 🎯 Parameter | ⚡ Description |
|---|---|
| W2 | Weight of dried extract after oven drying |
| W1 | Weight of test specimen (2 g) |
| P | Proportion of moisture-free wood (from drying test) |
💡 Tip: Ensure at least six to eight siphonings per hour for complete extraction. Adjust boiling rate if necessary.
❓ Frequently Asked Questions
🔍 Question: What is the purpose of using two test specimens in the procedure?
Answer: One specimen is used to determine the moisture content and calculate the proportion of moisture-free sawdust, while the other is extracted with dichloromethane to determine the soluble content. This allows for accurate reporting on a moisture-free basis.
💡 Question: Why is the extraction performed in a fume hood?
Answer: Dichloromethane is hazardous; it causes narcosis when inhaled and can irritate the eyes. All steps involving dichloromethane must be carried out in a fume hood to ensure proper ventilation and safety.
⚡ Question: How is the proportion of moisture-free sawdust (P) calculated?
Answer: The air-dry specimen is dried in an oven at 100 to 105°C until constant weight. The proportion P is the ratio of the moisture-free weight to the original air-dry weight.
📌 Question: What sieve sizes are used for the sawdust test specimen?
Answer: The sawdust must pass through a 425-µm (40 mesh) sieve and be retained on a 250-µm (60 mesh) sieve.