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D5352-95 – Standard Test Method Technical Guide
📜 Standard Scope and Significance
ASTM D5352-95 (Reapproved 2019) describes a test method for determining organically combined sulfuric anhydride in sulfonated or sulfated oils. The method involves extracting the undecomposed sulfonated or sulfated fat over an acidulated, concentrated salt solution and ashing the purified extract. It is applicable to all types of sulfonated and sulfated oils, including true sulfonic acid oils and those containing sodium acetate or similar partially titratable compounds. This test method was derived from Test Methods D500, Sections 25 through 28. Values are stated in SI units as standard. The test method is intended for the determination of organically combined sulfuric anhydride in sulfonated and sulfated fats and oils.
🧪 Reagents and Procedure
The procedure requires specific reagents: Ethyl Ether as solvent, Hydrogen Peroxide (30%) for oxidation, Methyl Orange Indicator Solution (1 g/L) prepared by dissolving 0.1 g in 100 mL water, solid Sodium Chloride for brine, and anhydrous Sodium Sulfate for dehydration. The sample is dissolved in a solvent, acidified, and washed with saturated brine. If ammonia is present, it must be expelled first. The purified extract is obtained by combining ether layers, dehydrating with 5 g of anhydrous Na2SO4, shaking vigorously for 5 minutes, and filtering directly into a 150-mL beaker placed in a warm water bath. The filter and flask are washed with ether until free from fat.
| 🟦 Step | 📏 Detail |
|---|---|
| Dehydration | Add 5 g anhydrous Na2SO4, shake for 5 min |
| Filtration | Filter into 150-mL beaker in warm water bath |
| Evaporation | Reduce ether volume to about 20 mL |
| Transfer | Use tared 50-mL crucible (high form) |
| Rinsing | Beaker rinsed with two 10-mL and three 5-mL ether portions |
| Limit | Beaker volume not to exceed 50 mL during filtering and washing |
The ether solution is evaporated until the volume is about 20 mL, then transferred to a tared 50-mL crucible immersed in warm water to evaporate residual ether. The beaker is rinsed with two 10-mL and three 5-mL portions of ether, allowing each portion to evaporate before the next.
🔥 Ashing and Determination
After the solvent-free residue is obtained, it is burned gently and finally ignited at a dull red heat. The ash corresponds to the organically combined sulfuric anhydride content. Care must be taken to avoid creeping of the oil during the process, which can lead to inaccurate results.
💡 Tip: To avoid creeping, ensure the volume in the beaker does not exceed 50 mL during filtering and washing. Also, allow each rinsing ether portion to evaporate before adding the next.
⚠️ Warning: Ethyl ether is highly flammable and hydrogen peroxide is a strong oxidizer. Use appropriate safety measures including working in a fume hood and avoiding ignition sources.
❓ Frequently Asked Questions
🔍 Q: What is the purpose of D5352-95?
A: It determines organically combined sulfuric anhydride in sulfonated or sulfated oils.
💡 Q: How is the sample prepared if it contains ammonia?
A: Ammonia must be expelled before the determination is made.
⚡ Q: What is the role of anhydrous sodium sulfate?
A: It dehydrates the ether layer after shaking for 5 minutes.
📌 Q: What crucible size is specified?
A: A tared 50-mL high-form crucible is used for ashing.