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D49-83 – Standard Test Method Technical Guide
⚗️ Scope, Sample Treatment, and Reagent Specifications
ASTM D49‑83 (Reapproved 2020) provides standard test methods for the chemical analysis of red lead pigments having the approximate formula Pb3O4, represented as PbO2·2PbO. These procedures are essential for verifying pigment composition and purity for quality control in paints and coatings. The standard explicitly states that values in SI units are to be regarded as the standard.
Treatment of the Sample
Accurate results depend on rigorous sample preparation. If the pigment is lumpy or not finely ground, it must be ground to a fine powder and mixed thoroughly. Large samples must be thoroughly mixed and a representative portion taken for powdering. In all cases, the sample must be thoroughly mixed before withdrawing portions for analysis. All samples shall be preserved in stoppered bottles or containers to prevent moisture absorption or contamination.
Purity of Reagents and Water
Reagent grade chemicals are required for all tests, conforming to the specifications of the Committee on Analytical Reagents of the American Chemical Society (ACS) where available. Unless otherwise indicated, references to water throughout the standard mean reagent water conforming to Type II of Specification D1193.
⚠️ Health and Safety Compliance: This standard does not purport to address all safety concerns. Red lead is a toxic substance. It is the responsibility of the user to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
| 🟦 Parameter | 📏 Specification / Value |
|---|---|
| Standard Designation | D49‑83 (Reapproved 2020) |
| 📐 Chemical Formula | Pb₃O₄ (PbO₂·2PbO) |
| 🎯 Reagent Grade | ACS Reagent Grade |
| ⚡ Water Specification | Type II per D1193 |
| 📦 Sample Containers | Stoppered bottles or containers |
💧 Moisture Determination and Organic Color Test
The standard outlines specific procedures to determine the moisture content and evaluate the presence of organic coloring matter in the red lead pigment.
Moisture Content
Moisture is determined using a 2‑gram specimen in accordance with Method A of Test Methods D280. The specimen is dried in an oven for exactly 2 hours at a temperature of 105°C. The resulting loss in weight is directly calculated and reported as the moisture content of the pigment. This parameter is critical for assessing storage quality and formulation performance.
💡 Precision Tip: Strict control of the oven temperature (105°C ± 2°C) and precise timing of the full 2‑hour drying period are required to achieve reproducible moisture results.
Organic Coloring Matter
To test for organic dyes or stains, boil 2 g of the sample with 25 mL of 95% ethyl alcohol. Allow the mixture to settle, then decant the supernatant liquid. Boil the remaining residue with 25 mL of distilled water and decant again. The complete absence of color in both the decanted alcohol and water indicates a pure, uncontaminated red lead pigment.
| 🟦 Test | 📐 Specimen Mass | 🎯 Reagent / Condition | ⚡ Duration / Temperature |
|---|---|---|---|
| Moisture (D280) | 2 g | D280, Method A | 2 h at 105°C |
| Organic Color | 2 g | 25 mL 95% Ethanol / 25 mL Water | Boiling / Decantation |
📊 Measured Properties and Referenced Standards
The primary measured properties derived from these methods are the percentage of moisture (by loss in weight) and the qualitative assessment of organic impurities. For a complete chemical analysis, D49‑83 references several other ASTM standards: D50 (Iron and Manganese), D215 (White Linseed Oil Paints), D1208 (Common Properties of Pigments), D1301 (White Lead), and D1959 (Iodine Value). Originally approved in 1917 and reapproved in 2020, this standard provides a long-standing foundation for inter‑laboratory quality assurance of red lead pigments.
❓ Frequently Asked Questions
🔍 What is the specific chemical composition of the red lead targeted by D49‑83?
The standard applies to red lead with the approximate formula Pb3O4, probably PbO2·2PbO.
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.