Phosphoric, more precisely, orthophosphoric acid has chemical formula H3PO4. Represents itself colourless crystals, very hygroscopic, well soluble in water. When heating over 200 degrees begin process of dehydration of orthophosphoric acid with education pyrophosphoric, on the following mechanism: 2H3PO4 = H4P2O7 + H2O. How it is possible to receive orthophosphoric acid?
Instruction
1. In the industry there are two main methods: thermal and extraction. When using thermal, phosphorus is oxidized oxygen (during burning) to phosphoric anhydride thus: 4P + 5O2 = P4O10
2. Then the formed phosphoric anhydride is exposed to hydration that leads to receiving orthophosphoric acid: P4O10 + 6H2O = 4H3PO4 When using this method, turns out the purest orthophosphoric acid.
3. The extraction method consists in release (extraction) of the orthophosphoric acid concentrated by sulfuric acid of a grinding of natural minerals-phosphates. In strongly simplified look, for that case when mineral consisted mostly of calcium phosphate, it is possible to write down this reaction so: Са3(РО4) 2 + 3H2SO4 = 2H3PO4 + 3CaSO4
4. Sulfuric acid, being much stronger, easily forces out weak orthophosphoric acid from its salts. The formed calcium sulfate, being slightly soluble substance, separates filtering. Orthophosphoric acid is purified from impurity.
5. In laboratory it is possible to receive this substance by interaction of white phosphorus with the diluted nitric acid. Reaction proceeds as follows: 3P + 5HNO3 + 2H2O = 3H3PO4 + 5NOOpasnost this method that it is necessary to use white phosphorus – extremely toxic agent. Therefore at its carrying out it is necessary to remember precautionary measures.