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D5351-93 – Standard Test Method Technical Guide
🔬 Apparatus and Reagent Specifications
The test method mandates a specific apparatus for the accurate extraction and boiling of samples. The setup requires a 300 mL borosilicate glass Erlenmeyer flask with a glass stopper connected to an air condenser via a standard taper ground joint. Perforated glass beads (approx. 4 mm in diameter) made of chemically resistant glass are essential to prevent bumping and must be pre-boiled until neutral to methyl orange.
| 🟦 Component | 📏 Specification | 🎯 Requirement |
|---|---|---|
| Flask | Erlenmeyer, 300 mL capacity | Borosilicate glass, glass stopper |
| Condenser | 915 mm (36 in.) length, 8 mm (5/16 in.) OD | Lower end flared and ground to fit the flask mouth |
| Glass Beads | ~4 mm (5/32 in.) diameter | Perforated, chemically resistant, boiled to neutrality |
⚙️ Test Procedure and Reagent Preparation
The procedure extracts undecomposed sulfated fat over an acidulated, concentrated salt solution. The solvent is evaporated, and the residue is boiled with sulfuric acid. The reaction products are then titrated using a standard sodium hydroxide solution. The strength of the 1 N NaOH solution must be accurately expressed as mg of KOH per mL.
| 🧪 Reagent | 📐 Concentration | ⚡ Equivalence / Note |
|---|---|---|
| Methyl Orange | 1 g/L (0.1 g / 100 mL H₂O) | Endpoint indicator for titration |
| Sodium Hydroxide | 1 N Standard Solution | 1 mL ≡ 56.1 mg KOH |
| Sodium Hydroxide | 0.5 N Standard Solution | Accurately prepared and standardized |
💡 Key Principle: This test method, derived from D500 and ALCA Method H-43, is applicable only to sulfated oils that split off their combined SO₃ upon boiling