Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5554-15 – Standard Test Method Technical Guide
📐 Scope and Significance
This test method, designated ASTM D5554-15 (Reapproved 2021), covers the determination of the iodine value of fats and oils that do not contain conjugated double bonds. The iodine value is a measure of unsaturation, expressed in centigrams of iodine absorbed per gram of sample. Values are in SI units, and the standard follows internationally recognized principles on standardization.
🧪 Apparatus, Reagents, and Procedure
The test requires specific apparatus and high-purity reagents. Key apparatus include 500 mL glass-stoppered bottles or flasks, 1000 mL volumetric flasks conforming to NIST tolerances, and pipettes of 20 mL and 25 mL. Reagents include glacial acetic acid (A.C.S. grade), potassium iodide, chlorine (99.8%), carbon tetrachloride, cyclohexane, and hydrochloric acid (sp. gr. 1.19). The diluting reagent is a 1:1 mixture of cyclohexane and glacial acetic acid, which must be tested for oxidizable matter.
| 🟦 Apparatus | 📏 Specification |
|---|---|
| Glass-Stoppered Bottles or Flasks | 500 mL, wide mouth for mechanical stirring |
| Volumetric Flasks | 1000 mL, NIST tolerances |
| Pipette | 20 mL |
| Pipettes for Dichromate | 25 mL, NIST tolerances |
⚠️ Safety Alert: Carbon tetrachloride is a known carcinogen. It is toxic by inhalation, ingestion, and skin absorption. Always handle inside a fume hood with adequate ventilation.
| 🧪 Reagent | 📐 Grade/Specification |
|---|---|
| Glacial Acetic Acid | A.C.S. grade, subject to permanganate test |
| Potassium Iodide | A.C.S. grade |
| Chlorine | 99.8% purity, dried through sulfuric acid |
| Carbon Tetrachloride | A.C.S. grade, handle with caution |
| Cyclohexane | A.C.S. grade |
| Hydrochloric Acid | A.C.S. grade, sp. gr. 1.19 |
💡 Technical Tip: For the diluting reagent, mix fresh cyclohexane and glacial acetic acid (1:1 v/v). Verify absence of oxidizable matter by shaking 10 mL of reagent with 1 mL of saturated potassium dichromate and 2 mL of concentrated sulfuric acid; no green color should appear.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D5554-15?
It covers determination of iodine value of fats and oils without conjugated double bonds.
💡 What safety measures are needed for carbon tetrachloride?
Handle only in a fume hood due to its carcinogenic and toxic properties.
⚡ How is the iodine value expressed?
As centigrams of iodine absorbed per gram of sample.
📌 Why is the permanganate test performed on acetic acid?
To ensure the acetic acid is free from oxidizable impurities that could affect results.