๐ฌ 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.
๐ฏ 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.
๐งฉ 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.
๐️ Written by Er. Rajeev's Stemfact.in.
๐งช 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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