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D4904-99 – Standard Test Method Technical Guide
📏 Specimen and Environmental Conditions
The specimen covered by this practice consists of 1‑L or 2‑L analytical solutions prepared according to ASTM Practices D4901, D4905, or D6405 for vegetable tannin analysis. Proper cooling of these solutions is essential because the solubility of extracts is influenced by temperature. The solutions must be cooled in an environment free from drafts, with ambient temperatures strictly maintained between 23 °C and 28 °C. The practice is adapted from ALCA Method A12 and is a replacement for that official method.
⚙️ Cooling Procedure and Temperature Control
The cooling procedure requires the prepared solutions to stand overnight in the specified ambient temperature range of no less than 23 °C and no more than 28 °C. After the temperature has been adjusted, the solutions are brought to the mark with distilled water at 23 °C. Where a constant temperature room is available, solutions protected from drafts may be cooled therein, with the room controlled so that flasks remain at 24 °C. This standardized approach prevents chilling, under‑cooling, or uneven cooling that could compromise tannin analysis results.
| 🟦 Parameter | 📏 Specification | ⚡ Requirement |
|---|---|---|
| Ambient Cooling Temperature | 23 °C to 28 °C | Stand overnight |
| Make‑up Water Temperature | 23 °C | Distilled water |
| Constant Temperature Room Setting | 24 °C | Maintain flask temperature |
| Specimen Volume | 1‑L or 2‑L | Per D4901, D4905, D6405 |
🔍 Significance and Key Considerations
The solubility of tanning extracts is significantly influenced by temperature. Analytical solutions dissolved or diluted in hot water must be cooled with caution to avoid chilling, under‑cooling, or uneven cooling. These factors can directly impact the accuracy of tannin analysis results. Adherence to this practice ensures reproducibility and reliability in testing.
💡 Tip: Always protect your solutions from drafts during cooling. Even slight air currents can cause uneven temperature distribution, leading to inconsistent results. Use a draft shield or a controlled‑environment enclosure.
⚡ Warning: Do not place hot solutions directly in cold environments. Rapid or uneven cooling can cause precipitation of extracts or inaccurate volume adjustments. Follow the specified temperature range closely and allow the full overnight equilibration.
❓ Frequently Asked Questions
🔍 Why must cooling conditions be standardized?
Standardized cooling conditions ensure reproducible tannin analysis results, as the solubility of extracts varies with temperature. Uncontrolled cooling can lead to inaccuracies in the final determination.
💡 What is the consequence of chilling or uneven cooling?
Chilling or uneven cooling can cause precipitation of tannins or miscalculation of solution volume, compromising the accuracy of the analysis.
⚡ What temperature range is required for ambient cooling?
The ambient temperature during cooling must be between 23 °C and 28 °C, with solutions standing overnight to equilibrate.
📌 Can I use a constant temperature room?
Yes, if available. The room should be controlled so that flasks remain at 24 °C, and solutions must be protected from drafts.