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D126-87 – Standard Test Method Technical Guide
🎯 Scope and Classification of Pigments
ASTM D126-87 (Reapproved 2023), under the jurisdiction of ASTM Subcommittee D01.31, establishes standardized test methods for the chemical analysis of pigments containing lead chromate and chromium oxide green. This scope specifically covers Chrome Yellow, Chrome Orange, Molybdate Orange, Pure Chrome Green, Reduced Chrome Green, and Chromium Oxide Green. The standard mandates SI units and references key companion documents including ASTM D280 (Hygroscopic Moisture) and D1193 (Reagent Water).
✅ Standard Status: This version (D126 – 87 (2023)) has been reapproved in 2023, confirming its continued relevance for quality control and regulatory compliance. It remains approved for use by agencies of the U.S. Department of Defense.
🔬 Analytical Test Procedures and Parameters
The standard organizes procedures by pigment category. Organic colors and lakes are determined qualitatively by sequential boiling in water, ethyl alcohol, and chloroform. Moisture and volatile matter follow ASTM D280, Test Method A. The table below details the specific analytes and sections for each pigment type.
| 🟦 Pigment Category | 📐 Analyte / Property | ⚡ Section(s) |
|---|---|---|
| Chrome Yellow, Chrome Orange, Molybdate Orange | Organic Colors & Lakes | 7 |
| Moisture & Volatile Matter | 8 | |
| Matter Soluble in Water | 9 | |
| Lead Chromate (PbCrO₄) | 10-11 | |
| Total Lead (Pb) | 12 | |
| Sulfate (SO₄) | 13-14 | |
| Carbon Dioxide (CO₂) | 15 | |
| Molybdenum (Mo) | 16-17 | |
| Pure & Reduced Chrome Green | Organic Colors & Lakes | 25 |
| Iron Blue | 28 | |
| Lead Chromate (PbCrO₄) | 29-30 | |
| BaSO₄ & Insoluble Siliceous Material | 31 | |
| Calcium Oxide (CaO) Soluble in Acid | 34-35 | |
| Extenders | 36 | |
| Calculation of Insoluble Lead Compounds | 37 | |
| Chromium Oxide Green | Organic Colors & Lakes | 38 |
| Moisture & Volatile Matter | 39 | |
| Matter Soluble in Water | 40 | |
| Total Chromium as Cr₂O₃ | 41 |
⚠️ Safety Advisory: Specific hazard statements are provided in Note 3 of the standard. Users handling lead chromate pigments must establish appropriate safety, health, and environmental practices in accordance with Section 1.4 and all applicable regulatory limitations.
📊 Calculation of Components and Extenders
Accurate calculation is critical for compliance. Sections 23 and 24 detail the calculation of “Substances Other than Insoluble Lead Compounds” for Chrome Yellows and Oranges. For Chrome Greens, Section 37 provides the framework for calculating insoluble lead compounds and extenders based on determined Iron Blue, sulfate, and barium content. Chromium Oxide Green utilizes Section 41 for total chromium calculation.
| 🔍 Component | 📏 Calculation Basis | 📊 Applicable Section |
|---|---|---|
| Substances other than insol. Pb compounds | Gravimetric / Volumetric Analysis | 23-24 |
| Insoluble Lead Compounds (Chrome Green) | Calculation from PbCrO₄, BaSO₄, Fe₄[Fe(CN)₆]₃ | 37 |
| Total Chromium as Cr₂O₃ | Oxidation-reduction titration | 41 |
💡 Technical Tip: When analyzing Pure Chrome