Phosphoric acid: Characteristics
Why battery-grade acid must be far cleaner
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.Merchant acid is sold by P2O5 content, with limits on solids and impurities that affect DAP quality and handling. Food and battery grades need far lower iron, heavy metals and fluorine.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Strength | merchant grade 52-54% P2O5; superphosphoric acid 68-70% P2O5 (indicative) | Price is per t P2O5; higher strength saves freight | Industry grades (indicative) |
| Solids | typically under about 1% (indicative) | Sludge settles in tankers and storage | Industry specifications (indicative) |
| Cadmium | EU fertiliser limit 60 mg/kg P2O5 | Market access to the EU | EU 2019/1009 |
| Iron, aluminium, magnesium (minor element ratio) | watched closely; high values lower DAP grade (indicative) | Sets DAP nitrogen and P2O5 content | Phosphate tile (indicative) |
| Fluorine | feed and food grades under about 0.1-0.2% F relative to P (indicative) | Fluorine is toxic to animals | Indicative |
Commercial grades
- Merchant-grade acid (52-54% P2O5) for fertiliser
- Superphosphoric acid for liquid fertilisers
- Feed-grade defluorinated acid
- Food grade (85% H3PO4)
- Technical and battery grade for LFP
- Electronic grade for etching