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D2165-94 – Standard Test Method Technical Guide
📜 Standard Overview and Significance
The ASTM D2165-94 (Reapproved 2012) standard provides a definitive framework for assessing the pH of aqueous extracts derived from wool and similar animal fibers. This quantitative value serves as a direct indicator of the residual acidity or alkalinity present on the fiber and its water-soluble impurities, offering essential insight into its chemical processing history. The method is broadly applicable to fibers in any stage of production, including raw wool, scoured wool, sliver, top, yarn, and fabric forms.
| 🟦 Component | 📏 Specification |
|---|---|
| Glassware (Contact Surfaces) | Chemical-resistant glass; soaked 2 days in 0.1 N HCl; rinsed to pH ≥ 6.0 |
| Distilled Water | pH range 6.0 – 7.0, free of carbon dioxide (CO₂) |
| Sodium Chloride Solution | 0.1 N NaCl |
| pH Meter | Conforms to Test Method E70; readable to 0.02 pH units |
⚠️ Inter-Laboratory Precision: This test method is not recommended for acceptance testing due to relatively poor between-laboratory precision. In the event of a dispute, a statistical bias analysis should be conducted between the purchaser and seller laboratories using specimens randomly drawn from a single sample of the material.
⚗️ Essential Apparatus and Reagents
The standard mandates stringent cleanliness and preparation protocols for all materials. The user has the option of four distinct extraction procedures, utilizing either boiling under reflux or room temperature agitation, with either distilled water or 0.1 N sodium chloride solution as the extractant. The choice of procedure depends on which index of acidity or alkalinity is the most informative for the specific fiber history.
| ⚙️ Procedure | 🌡️ Temperature | 💧 Extractant Liquid | ⏱️ Duration |
|---|---|---|---|
| A | Boiling (Reflux) | Distilled Water | 60 minutes |
| B | Room Temp (Agitation) | Distilled Water | 60 minutes |
| C | Boiling (Reflux) | 0.1 N NaCl Solution | 60 minutes |
| D | Room Temp (Agitation) | 0.1 N NaCl Solution | 60 minutes |
💡 Glassware Maintenance: It is highly recommended to reserve the glassware exclusively for these extraction tests. Filling the containers with distilled water during storage periods between tests helps maintain an optimal, contaminant-free environment.
⚙️ Extraction Procedure and pH Measurement
A minimum test specimen of 5 g is extracted with 100 mL of the selected extractant (or 10 g with 200 mL). For procedures A and C, the specimen is combined with the extractant, heated to the boil, and refluxed for 60 minutes. For procedures B and D, the specimen is agitated at room temperature for 60 minutes. The extract is then decanted or centrifuged and cooled to room temperature before measurement.
The pH of the extract is measured electrometrically using a glass electrode. The instrument must be calibrated per Test Method E70. The temperature of the extract is recorded, and the pH value is reported to the nearest 0.1 pH unit. The report must clearly identify the extraction procedure used (A, B, C, or D) and the measurement temperature.
❓ Frequently Asked Questions
🔍 What fiber forms are covered by the standard?
The standard is explicitly applicable to wool and similar animal fibers in any physical condition, including raw wool, scoured wool, sliver, top, yarn, and fabric.
💡 Why does the standard offer four different extraction procedures?
Different procedures (boiling vs. room temperature, water vs. saline) extract different soluble components, providing tailored information about processing history or fiber condition. The choice depends on the specific index of acidity or alkalinity sought by the analyst.
⚡ What is the minimum specimen size required for a single extraction test?
The minimum specimen size is 5 g, which is extracted with 100 mL of the selected extractant. Alternatively, a larger 10 g specimen can be extracted with 200 mL of the liquid.
📌 How should the final test results be reported?
The pH value must be reported to the nearest 0.1 pH unit. The report must clearly identify the extraction procedure used (A, B, C, or D) and the temperature at which the pH measurement was taken.