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D1847-93 – Standard Test Method Technical Guide
🔬 Scope and Summary of Test Methods
These test methods, designated D 1847 – 93 (Reapproved 1998), are under the jurisdiction of ASTM Committee D-1 on Paint and Related Coatings. They specifically cover the determination of the total chlorine content of epoxy resins in concentrations below 1 weight percent. An epoxy resin is defined as the reaction product of a chlorohydrin and a di- or polyfunctional phenolic compound. The method measures both organic and inorganic chlorine compounds contained in the resin.
The summary of the test method involves oxidizing the resin by combustion in a bomb containing oxygen under a pressure of 40 atm. The chlorine compounds thus liberated are absorbed in a sodium carbonate solution. The standard includes two alternative methods for determining the chloride ion concentration: Test Method A (Potentiometric Titration, Sections 6-10) and Test Method B (Gravimetric Determination, Sections 11-15).
⚙️ Apparatus and Reagent Specifications
Precise equipment and high reagent purity are essential for accurate results. The combustion apparatus must be a standard oxygen bomb rated for 40 atm pressure. For the potentiometric method, a suitable pH meter equipped with a glass-silver electrode system, titration stand, stirrer, and a 10-mL buret is required.
| 🟦 Reagent / Equipment | 📏 Specification | 🎯 Primary Method |
|---|---|---|
| Oxygen Bomb | 40 atm pressure, halogen-free oxygen | Both Methods |
| Silver Nitrate Solution | 0.01 N (1.70 ± 0.01 g AgNO₃ per Litre) | Method A (Titrant) |
| Methyl Red Indicator | 0.2 % w/v in alcohol (methanol/ethanol/isopropanol) | Method A |
| Nitric Acid | Concentrated (sp gr 1.42) | Method A |
| Reagent Water | Type II per Specification D 1193 | Both Methods |
⚠️ Safety and Purity Alert: The oxygen used in the bomb must be completely free of combustible materials and halogen compounds. All reagents must conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society to prevent interference.
💡 Significance and Key Measured Properties
The total chlorine content of epoxy resins is an important variable in determining the reactivity of the resin and the performance of coatings prepared from them. These test methods are used to confirm specification limits for manufactured epoxy resins. The choice between the potentiometric and gravimetric approaches depends on available instrumentation, but both procedures analyze the absorbed sodium carbonate solution resulting from the initial bomb combustion.
| ⚡ Feature | 📐 Test Method A (Potentiometric) | 📐 Test Method B (Gravimetric) |
|---|---|---|
| Detection Principle | Potentiometric endpoint (voltage shift) | Mass of precipitated AgCl |
| Key Instrumentation | pH meter, silver electrode, 10 mL buret | Analytical balance, filtering crucible |
| Standard Solution Required | 0.01 N Silver Nitrate | Silver Nitrate (for precipitation) |
| Chlorine Source Measured | Total (Organic & Inorganic) | Total (Organic & Inorganic) |
💡 Key Implementation Note: The 0.01 N silver nitrate solution for Method A is prepared by dissolving exactly 1.70 ± 0.01 g of crystalline silver nitrate in reagent water. For the gravimetric method, the precipitated silver chloride is weighed to determine the total chlorine content.
❓ Frequently Asked Questions
🔍 What concentration range does ASTM D1847-93 cover?
These test methods are specifically designed for determining total chlorine content at concentrations below 1 weight percent in epoxy resins.
💡 Does this method differentiate between organic and inorganic chlorine?
No. The combustion process in the oxygen bomb converts all chlorine compounds into chloride ions. The method measures the total chlorine content from both organic and inorganic sources.
⚡ What is the required pressure for the oxygen bomb combustion?
The standard specifies that the oxygen used in the bomb must be at a pressure of 40 atm and must be free of combustible materials.
📌 What are the section references for the two test methods?
Test Method A (Potentiometric Titration) is covered in Sections 6-10, while Test Method B (Gravimetric Determination) is covered in Sections 11-15 of the standard.