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D4907-10 – Standard Test Method Technical Guide
🔬 Apparatus and Reagents Specification
The following equipment and solutions are required per ASTM D4907-10:
| 🟦 Component | 📏 Specification |
|---|---|
| Watch Glass | Borosilicate glass, 100 mm diameter |
| Reagent Bottles | Two, 4 fl oz each, with glass joint dropping pipet |
| Indicator Solution | 0.1 g diphenylamine in 100 mL H₂SO₄ + 30 mL distilled H₂O |
| Blank Solution | 100 mL sulfuric acid + 30 mL distilled water |
| Test Specimen | Approximately 1 cm² of finished leather |
Hazard Warning: All chemicals used in this test method, including sulfuric acid and acetone, are hazardous. Always consult the Material Safety Data Sheet (MSDS) and use appropriate personal protective equipment.
⚙️ Test Procedure
The test method involves applying indicator or blank solution to the leather specimen and observing color changes:
Step 1: Place the specimen finish side up on a watch glass. Apply 1–2 mL of indicator solution and allow it to run over the leather. After 3 minutes, if no dark blue color develops, nitrocellulose is absent. A dark blue color may indicate nitrocellulose or interference from colored finish components.
Step 2: Repeat the test using the blank solution. If the indicator produces a dark blue color but the blank does not, nitrocellulose is present without interference from colored materials.
Step 3: If both solutions produce a dark blue color, extract the specimen with acetone. Place the specimen in a watch glass, cover with acetone, and soak for 2 minutes. Remove the specimen and evaporate the acetone to dryness in a steam oven. After cooling, apply a few drops of indicator solution at one location on the watch glass rim and blank solution at another location. Allow the drops to run downward. A dark blue color only from the indicator confirms the presence of nitrocellulose.
If both indicator and blank produce color, the acetone extraction step is essential for eliminating interference from colored finishes.
📊 Interpreting Test Results
The presence of nitrocellulose is determined based on color development under different conditions:
| 🎯 Test Condition | ⚡ Indicator Result | ⚡ Blank Result | 📌 Conclusion |
|---|---|---|---|
| Direct test (Step 6.1) | Dark blue | Not used | Nitrocellulose may be present; verify with blank |
| Blank test (Step 6.2) | Dark blue | No color | Nitrocellulose present, no interference |
| Both develop color (Step 6.3 before acetone) | Dark blue | Dark blue | Colored components interfere; proceed to acetone extraction |
| After acetone extraction (Step 6.3) | Dark blue | No color | Nitrocellulose confirmed |
Note: No color development with the indicator in Step 6.1 indicates the absence of nitrocellulose.
❓ Frequently Asked Questions
🔍 What types of leather can be tested with this method?
This test method applies to all types of finished leathers but is not intended for wet blue leather.
💡 How is the indicator solution prepared?
Dissolve 0.1 g of diphenylamine in a mixture of 100 mL of sulfuric acid and 30 mL of distilled water.
⚡ What does a dark blue color indicate?
A dark blue color after applying indicator suggests the presence of nitrocellulose, but colored finish components may also cause this. The blank test and acetone extraction help differentiate.
📌 Why is acetone used in the test?
Acetone dissolves nitrocellulose, allowing it to be isolated from colored components for unambiguous detection.