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Send EmailNigrosin, Nigrosine, 8005-03-6, 68470-10-6
🔬 What Nigrosin Is
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Chemical nature: Nigrosin (CI 50415, Solvent Black 5) is a mixture of black synthetic dyes derived from heating nitrobenzene, aniline, and hydrochloric acid with copper or iron catalysts.
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Structure: It belongs to the phenazine-based dye family, related to induline.
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Variants: Sulfonated nigrosin (Nigrosin WS, CI 50420, Acid Black 2) is water-soluble and used in aqueous applications.
⚙️ Industrial Uses
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Colorant for lacquers and varnishes – gives deep black coloration.
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Marker pen inks – widely used due to its strong, stable black pigment.
🧫 Biological & Laboratory Uses
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Negative staining in microbiology: Nigrosin does not penetrate live cells, so it stains the background instead. This makes bacteria and fungi (e.g., Cryptococcus neoformans) visible as clear outlines.
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Sperm viability tests: In combination with eosin (Eosin-Nigrosin test), it helps distinguish live from dead sperm cells. Eosin stains damaged cells red, while nigrosin provides a dark background for contrast.
📌 Key Points for Practical Use
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Non-toxic to live cells: Since it doesn’t penetrate intact membranes, it’s ideal for viability assays.
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Contrast enhancer: Provides sharp visibility of cell outlines, capsules, or external structures.
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Water-soluble form (Nigrosin WS): Preferred when working in aqueous biological systems.
⚠️ Risks & Considerations
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Handling: As with most synthetic dyes, nigrosin should be handled with gloves and protective equipment to avoid skin staining or inhalation.
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Verification: Always confirm whether you need solvent-based nigrosin or water-soluble nigrosin depending on your application.
📑 Nigrosin – Synonyms & Alternative Names
| Category | Name / Code |
|---|---|
| General Trade Names | Nigrosin, Nigrosine |
| Color Index (CI) | CI 50415 (Solvent Black 5), CI 50420 (Acid Black 2 – sulfonated form) |
| Chemical Descriptions | Phenazine-based dye mixture, Induline-type dye |
| CAS Numbers | 8005-03-6 (Nigrosin), 68470-10-6 (Nigrosin WS) |
| Industrial Codes | Solvent Black 5, Acid Black 2 |
| Laboratory Usage Names | Eosin-Nigrosin stain, Negative stain dye |
| Other Labels | Water-soluble Nigrosin (Nigrosin WS), Nigrosin Base |
🔎 Key Notes
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Solvent Black 5 → Organic solvent-soluble form.
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Acid Black 2 (Nigrosin WS) → Water-soluble form, preferred in microbiology.
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Induline-type dye → Classified due to its phenazine-derived structure.
📊 Nigrosin – Sectoral Suitability Table (
| Sector | Application | Compliance / Standards | Risks / Notes |
|---|---|---|---|
| Chemical Industry | Lacquers, varnishes, inks, marker pen inks | Meets industrial dye/solvent standards | Not suitable for food or medical use |
| Textile Industry | Black pigmented prints, special effect dyes | REACH, OEKO-TEX compliance required | Limited use in direct-contact textiles; migration testing necessary |
| Biology / Microbiology | Negative staining, capsule detection, Eosin-Nigrosin test | ISO 17025 laboratory standards, biosafety rules | Not for clinical diagnosis, only research and teaching |
| Food Industry | — | Not suitable | Cannot be used as food additive |
| Pharmaceuticals | — | Not suitable | Not used in drug formulations |
| Research & Education | Microscopy, biology labs | Widely used in academic settings; biosafety compliance required | Lower concentrations recommended for student experiments |
🔎 Summary
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Industrial use: ✔️ (chemicals, textiles, inks)
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Laboratory use: ✔️ (microbiology, education)
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Food / pharma: ❌ (not suitable, prohibited)
