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D370-02 – Standard Test Method Technical Guide
📜 Scope and Significance
ASTM D370-02 outlines a standard practice for the dehydration of oil-type preservatives prior to distillation testing. The removal of water allows for distillation results to be reported on a dry basis, significantly enhancing the accuracy of compositional analysis. Quantitative determination of the water content itself must be conducted in accordance with Test Method D95. Sampling of the preservatives prior to testing is covered in Test Methods D38.
⚠️ Important Distinction: This practice is solely for dehydration to prepare a sample for further tests. If a precise measurement of the water content in the sample is required, refer strictly to ASTM D95 (Water in Petroleum Products and Bituminous Materials by Distillation).
📌 Regulatory Alignment: This practice is substantially in agreement with the American Wood-Preservers’ Association (AWPA) Standard Methods for Analysis of Creosote and Oil-Type Preservatives (A1) and is also designated as AASHTO No. T 83.
🔬 Apparatus Specifications and Assembly
The procedure requires a specific assembly of copper and glass apparatus to ensure efficient and consistent dehydration. The key components include a distillation still, condenser, and separatory funnel arranged precisely as described in the standard.
| 🟦 Component | 📏 Specification Details |
|---|---|
| Still | Vertical, cylindrical copper still with removable flanged top and yoke (See Fig. 1). |
| Thermometer | ASTM High Distillation Thermometer (8C or 8F per Specification E1). Range: -2 to +400°C or 30 to 760°F. Total immersion. |
| Condenser | Copper trough condenser fitted with a straight-walled glass tube (See Fig. 2). |
| Separatory Funnel | Total capacity approximately 200 mL, with the lower 20 mL graduated accurately in 0.1 mL increments. A Squibb type (approx. 100 mL) is also acceptable. |
The apparatus must be assembled as shown in Fig. 2 of the standard to ensure a proper vapor path through the condenser and accurate collection of the distillate.
⚙️ Dehydration Procedure
Obtaining a representative sample is critical for the validity of the dehydration process. The sample must be thoroughly mixed, and if the preservative is too viscous, it should be gently warmed to ensure complete liquidity and uniformity before a portion is withdrawn.
| 📌 Step | ⚡ Specification / Action |
|---|---|
| Sample Conditioning | Thoroughly stir the received sample. Warm if necessary to ensure liquidity and uniformity. |
| Portion Removal | Remove a representative portion strictly from the conditioned sample. |
| Distillation Volume | Transfer 200 to 300 mL of the representative portion into the copper still. |
| Dehydration | Water is removed from the preservative solution by distillation in the copper still. |
💡 Best Practices for Representative Sampling: Warming the sample is recommended only to achieve a pourable consistency, not to boil or fractionate the components. Overheating can alter the composition of the preservative before the main dehydration step.
Once the apparatus is assembled and the sample is conditioned, the 200 to 300 mL volume is transferred into the still. The sample is then heated until dehydration is complete. The condensed liquid is collected in the graduated separatory funnel, allowing the process to be monitored effectively.
❓ Frequently Asked Questions
🔍 What is the primary purpose of this practice?
The main goal is to prepare oil-type preservatives by removing water, allowing subsequent distillation tests to be reported accurately on a dry basis.
📌 Which ASTM standard covers the quantitative measurement of water?
ASTM D95 (Test Method for Water in Petroleum Products and Bituminous Materials by Distillation) is the reference standard for determining the specific amount of water present.
💡 How does one ensure a representative sample for dehydration?
The sample must be thoroughly stirred, and if necessary, warmed to ensure complete liquidity and uniformity, as outlined in Section 7 of the standard.
⚡ What type of thermometer is required for this