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D1860-95 – Standard Test Method Technical Guide
🧪 Scope and Summary of the Test Method
This standard, designated D1860 – 95 (Reapproved 2000), defines a distillation-extraction procedure for the simultaneous determination of moisture content and the amount of creosote or creosote-base preservative in wood. Its use is explicitly required over the standard oven drying method (Methods D 143) when the wood sample contains volatile oils or oil preservatives that would otherwise be lost during simple heating.
Summary: A precisely weighed wood sample is fully extracted by refluxing in toluene, xylene, or a mixed toluene-xylene solvent. The condensed vapors flow into a graduated water trap where the water separates and its volume is directly measured. The solvent is recycled back into the flask. Once extraction is complete, the wood sample is dried and weighed to determine the total loss in mass.
⚙️ Essential Apparatus and Specifications
The accuracy of this test method relies heavily on the precise specifications of the apparatus. The following table summarizes the key components and their required dimensions as detailed in Section 5 of the standard.
| 🟦 Component | 📏 Specification | 🎯 Required Value |
|---|---|---|
| Extraction Flask | Capacity | 500 mL |
| Water Trap | Inside Diameter | 9.0 to 10.0 mm |
| Water Trap | Graduated Capacity | 10 mL |
| Water Trap | Smallest Graduation | ≤ 0.1 mL |
| Extraction Basket | Mesh Size | 45-mesh (Stainless Steel) |
| Extraction Basket | Dimensions (OD x Length) | 42 mm x 127 mm |
| Condenser | Type | Cold-Finger or Liebig |
| Stirring Rod | Diameter | Approximately 3 mm |
To ensure optimal performance, the water trap must be chemically clean to maintain a consistent meniscus. The standard includes a specific procedure for treating the trap to achieve this uniformity.
| ⚡ Step | 📋 Action | ⚡ Parameter |
|---|---|---|
| 1 | Clean the glass trap | Use a sulfuric acid-chromic acid mixture |
| 2 | Rinse with coating agent | Silicone resin |
| 3 | Bake to cure resin | Approximately 200°C for 1 hour |
📊 Significance and Calculation
Significance: The moisture content of wood is a direct criterion for its treatability. Determining the preservative content of treated timber is essential for verifying the penetration of preservative in new stock and assessing the permanence of the preservative during the service life of the wood structure.
Calculation: The quantity of creosote-type preservative is derived from the total loss of weight of the wood sample during extraction, less the weight of the water removed. The water weight is obtained directly from the volume measured in the graduated water trap (1 mL of water approximates 1 g). The residual weight loss represents the mass of the oil-type preservative originally present in the specimen.
⚠️ Safety Alert: This test method uses hazardous materials. Toluene and xylene are flammable and toxic. The chromic acid cleaning mixture is highly corrosive and a strong oxidizer. Users must establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use, as stated in Scope 1.2.
💡 Technical Tip: A uniform meniscus in the water trap is critical for accurate volumetric readings. If the meniscus is inconsistent, thoroughly clean the trap and apply a silicone resin coating as described in Note 1 of the standard. This baking process provides a consistent surface for the water-solvent interface.
❓ Frequently Asked Questions
🔍 Why is this method preferred over oven drying for treated wood?
The standard oven-drying method (D 143) is unsuitable because the volatile components of the creosote-type preservative would evaporate along with the water in the oven, making it impossible to accurately distinguish between moisture and preservative content.
💡 Which solvents are specified for the extraction process?
The method permits the use of Nitration Grade Toluene (ASTM D 841), Ten-degree Xylene (ASTM D 846), or a mixture of toluene and xylene. The choice of solvent may depend on the specific characteristics of the preservative in the sample.
⚡ How is the preservative content determined from the test results?
The preservative content is calculated using a deductive method. The water volume collected in the trap is converted to mass. This mass is subtracted from the total weight loss of the wood sample. The remaining value represents the mass of the creosote or creosote-base preservative.
📌 What is the specified capacity and graduation of the required water trap?
The standard specifically requires a water trap with a graduated portion having a capacity of 10 mL. The smallest graduation on this tube must be no greater than 0.1 mL to ensure the precise measurement of extracted water.