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D1844-86 – Standard Test Method Technical Guide
📐 Scope and Referenced Documents
These test methods cover the chemical analysis of basic lead silicochromate pigment as defined in ASTM D1844-86 (Reapproved 2020). The pigment is commonly used in coatings and must be confirmed by X-ray diffraction analysis per Specification D1648. These methods apply to pigment supplied by the manufacturer and to pigment separated from liquid coatings. For liquid coatings, the pigment must first be separated from the vehicle before analysis (Section 1.2).
The standard references several ASTM standards including D185 (Coarse Particles), D280 (Hygroscopic Moisture), D281 (Oil Absorption), D387 (Color and Strength), D1193 (Reagent Water), D1648 (Basic Lead Silicochromate Pigment), and D2371 (Pigment Content).
⚙️ Analytical Test Methods and Procedures
The analytical procedures are presented in the following order for key components. Each component is determined through specific sections of the standard as listed below.
| 🟦 Component | 📏 Sections | 🎯 Purpose |
|---|---|---|
| Lead Oxide | 6 to 14 | Determination of lead oxide content |
| Chromium Trioxide | 15 to 23 | Determination of chromium trioxide content |
| Silica | 24 to 27 | Determination of silica content |
| Moisture and Other Volatile Matter | 28 | Measurement of hygroscopic moisture |
| Coarse Particles | 29 | Determination of coarse particles |
| Oil Absorption | 30 | Oil absorption by spatula rub-out |
| Mass Color and Tinting Strength | 31 | Color and strength testing |
💡 Tip: For liquid coatings, ensure that the pigment is completely separated from the vehicle to avoid interference in analysis (Section 1.2). Use Test Method D2371 for pigment content separation.
📊 Significance and Reagent Requirements
These test methods are used to confirm the lead oxide, chromium trioxide, and silica content of basic lead silicochromate, which is essential for quality control in pigment production and application. The procedures are designed for pigment only, not mixed pigments, and are applicable to pigment supplied by the manufacturer or separated from coatings.
All reagents must be ACS reagent grade where such specifications are available, unless otherwise indicated. Water must conform to Type II of Specification D1193. The use of high-purity reagents ensures accuracy of determinations. Other grades may be used if they do not affect accuracy.
The values are stated in SI units and are regarded as the standard, with values in parentheses for information only (Section 1.4).
⚠️ Warning: This standard does not address all safety concerns. Users must establish appropriate safety, health, and environmental practices (Section 1.5). Particular care is needed when handling lead and chromium compounds.
❓ Frequently Asked Questions
🔍 What is the scope of D1844-86?
It covers chemical analysis of basic lead silicochromate pigment, including tests for lead oxide (Sections 6–14), chromium trioxide (Sections 15–23), silica (Sections 24–27), moisture (Section 28), coarse particles (Section 29), oil absorption (Section 30), and mass color/tinting strength (Section 31). Confirmation by X-ray diffraction is required.
💡 How are reagents prepared?
Reagent grade chemicals conforming to ACS specifications should be used. Water must be Type II reagent water per Specification D1193. Other grades may be used if they do not lessen accuracy.
⚡ What is the significance of these tests?
They are used for quality control to confirm the lead oxide, chromium trioxide, and silica content of basic lead silicochromate pigment, ensuring consistency in industrial applications.
📌 Are there safety considerations?
Yes, users should establish safety practices due to the presence of lead and chromium compounds. The standard does not cover all safety concerns, and regulatory limitations should be considered (Section 1.5).