🔬 Industrial Preparation of Methyl Orange
Methyl orange is a widely‑used azo dye and pH indicator.
Photo: Industrial methyl orange reactor unit (via OpenPR). Credit: OpenPR.
1. What Is Methyl Orange?
A yellow to orange powder, methyl orange turns red in acid (pH ≤ 3.1) and yellow in alkaline (pH ≥ 4.4), making it ideal for titrations 2.
2. Industrial Process Overview
Step A: Diazotization
p‑Sulfanilic acid reacts with NaNO₂ in HCl at below 5 °C to form the diazonium salt 3.
Step B: Coupling
The diazonium salt couples with N,N‑dimethylaniline in acidic medium, then NaOH is added to form the sodium salt, yielding methyl orange crystals 4.
Step C: Isolation & Purification
Crystals are filtered, washed with brine, ethanol, ether, and dried. This gives a pure dye for industrial use 5.
3. Industrial Equipment & Conditions
Industrial scale uses large, cooled reactors, agitators, filtering units, and crystallizers. Raw materials are high‑grade acids and reagents 6.
4. Safety & Quality Control
Diazonium salts can be hazardous if dry — processes keep them wet. Temperature and pH are strictly monitored for quality and yield 7.
5. Applications
- Acid‑base titrations in labs.
- Textile dyeing and quality control.
- Research tool in analytical chemistry.
🎯 Quick Facts Table
| Property | Value |
|---|---|
| Formula | C₁₄H₁₄N₃NaO₃S |
| pH transition | 3.1 (red) → 4.4 (yellow) |
| Density | 1.28 g/cm³ |
| Solubility | 5 g/L at 20 °C |
6. Industrial vs Lab Process
Lab uses small flasks and test tubes, larger quantities, simpler isolation. Industrial uses large reactors, crystallizers, and automated purification for scale and cost efficiency.
🧩 Quiz Game: Score Your Knowledge!
1. What temperature is needed for diazotization?
2. The color change range of methyl orange is?
Score: 0/2
7. Embedding Videos & Images
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8. Summary
Industrial preparation of methyl orange follows diazotization → coupling → purification. Monitoring of pH and temperature ensures high purity yield for lab and textile use.
🖋️ Written by Er. Rajeev's Stemfact.in.
🧪 Free Chemistry PDF: Download 4 MCQs on Methyl Orange with answers. Useful for Class 10 & Olympiad practice.
Sample Question:
Which of the following describes the color change of methyl orange in base?
- A) Red
- B) Orange
- C) Yellow ✅
- D) Colorless
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