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D1958-86 – Standard Test Method Technical Guide
ASTM D1958 – 86 (Reapproved 1995) establishes a gravimetric test method for determining the percentage of matter in oiticica oil that remains insoluble in chloroform. This residue primarily represents mineral contamination, providing an essential purity metric for drying oils used in coatings and industrial applications.
🔬 Scope and Significance
The test method, as defined in Section 1.1, is specifically designed for oiticica oil but is also suitable for evaluating other drying oils. Section 2.1 highlights that while natural oil components are fully soluble in chloroform, mineral contaminants are not, making this an effective method for assessing the degree of solid impurity contamination.
| 🟦 Aspect | 📐 Requirement |
|---|---|
| Designation | D 1958 – 86 (R 1995) |
| Target Oils | Oiticica & other drying oils |
| Measured | Mineral Matter (Insolubles) |
| Principle | Gravimetric Filtration |
⚙️ Procedure and Calculation
⚠️ Important Safety Precaution: This method uses Chloroform (CHCl₃), as specified in Section 3.1. Section 4.1 warns that chloroform is a hazardous liquid which can be absorbed through the skin and its vapor is a narcotic hazard. It must only be used with adequate ventilation, specifically in a fume hood. Consult the material’s Safety Data Sheet (SDS) before handling.
Section 5.1 details the analytical procedure. A 10-gram sample is dissolved in chloroform and filtered through a pre-dried and weighed Gooch crucible. The crucible and any retained residue are washed, dried at 105 ± 2°C, cooled, and weighed. This drying process is repeated until a constant weight is achieved within 0.1 mg.
| 📏 Step | ⚡ Spec |
|---|---|
| Sample | 10 g |
| Solvent | Chloroform |
| Filter | Gooch Crucible |
| Dry Temp | 105 ± 2 °C |
| Weight Tolerance | ± 0.1 mg |
| Calculation (Section 6.1) | I = (R/S) × 100 |
💡 Precision & Bias Considerations: Section 7.1 states that formal precision and bias data were not established at the time of writing. Despite this, the test method has proven its usefulness over many years of use. Laboratories implementing this standard should conduct their own precision studies.
❓ Frequently Asked Questions
🔍 What does this test method measure?
It measures the percentage of mineral contamination in oiticica oil that is insoluble in chloroform, distinguishing it from soluble natural components.
💡 Why use a Gooch crucible?
The Gooch crucible (Section 5.1) provides a stable, high-temperature filtering surface for the repeated drying and weighing cycles required.
⚙️ What are the drying specifications?
Drying is performed at 105 ± 2 °C (Section 5.1) until the weight is constant to within 0.1 mg.
📌 Is this test only for Oiticica Oil?
No. Section 1.1 allows the test method to be used for other drying oils as well.