Usage areas of Phosphoric acid
Phosphoric acid is produced industrially by a wet method where sulfuric acid reacts with apatite (tricalcium phosphate rock).
Ca 5 (PO 4) 3 CI + 5H 2 SO 4 + 10H 2 O → 3H 3 PO 4 + 5 CaSO 4 2H 2 O + HCI
The resulting phosphoric acid solution is about 32-46% H3PO4, so it is then concentrated (by water evaporation) to produce a commercial grade of higher concentration of phosphoric acid.
Pure phosphoric acid is a white crystalline solid with a melting point of 42.35 °C. When less concentrated, it is a colorless, odorless, viscous liquid with a density of 1.885 g/mL. It is non-toxic and non-volatile. The most common concentration of H₃PO₄ is 85% in water.
Phosphoric acid has three acidic and replaceable H atoms. Thus, it reacts differently from other mineral acids. It can react with bases to form three classes of salts by replacing one, two, or three H atoms, such as NaH2PO4, Na2HPO4 and Na3PO4, respectively.
At high temperatures, H ₃PO₄ molecules can react and combine (with loss of water molecule) to form dimers, trimers, and even long polymeric chains such as polyphosphoric acids and metaphosphoric acids.
2H 3 PO 4 → lH 4 P 2 O 7 (- H 2 O)
- Acidification of soft drinks such as cola
- pH control in the production of imitation jellies
- Media component in yeast production
- Control of bacterial growth in selected processed food products
- Precipitating agent for clarification of sugar juices after liming
- Cleaning the tooth surface in dentistry and orthodontics
- Production of pesticides
- Lowering the pH of solutions in floriculture
- Production of phosphate salts
- Tanning and polishing stages of leather
- Surface corrosion protection in the steel industry
- Cleaning of unwanted catalysts in the oil industry
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