Hydrochloric acid: Characteristics
Why by-product acid is not always good enough
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.HCl is sold by concentration, typically 30-36%. Purity matters for food, pharma and electronics (iron, heavy metals, organics, fluoride). By-product acid can carry organics or fluoride that some users cannot accept, which separates it from synthetic acid.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Concentration | 30-36% HCl (commercial); 37% maximum at room temperature | sets freight cost per unit of HCl | standard property |
| Iron and heavy metals | ppm limits for food and pharma grades (indicative) | contamination of products | indicative |
| Free chlorine | low ppm in synthetic acid (indicative) | corrodes and oxidises | indicative |
Commercial grades
- Technical grade 30-33%
- Synthetic high-purity grade for food and pharma
- Electronic grade (ppb metals)
- Anhydrous HCl gas for semiconductors and silicon