Talk:Phosphoric acid/Archives/2021
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Boiling point
While the water evaporates, the acid does not. After reaching 100 % it keeps boiling due to condensation of H3PO4 to things like Oligophosphoric and polyphosphoric acids. The acid itself does not really boil. I will correct this in the article accordingly.
This paper has a Temperature-Composition Diagram for the System P2O5<->H2O. At 270 °C the vapour reaches just 0,1 % P2O5 content. 85 % H3PO4 in the vapor are reached at 61.5 % P2O5 and thus at about 800 °C
| Temp. Of boiling acid, °C | P4O10 in vapor, wt. % |
|---|---|
| 221-228 | 0.009 |
| 228-234 | 0.014 |
| 234-241 | 0.02 |
| 241-250 | 0.03 |
| 250 | 0.02 |
| 250-259 | 0.05 |
| 259-268 | 0.08 |
| 268-273 | 0.12 |
| 273-281 | 0.16 |
| 281-290 | 0.29 |
| 290-301 | 0.47 |
| 301-308 | 0.64 |
| 308-316 | 0.89 |
| 320 | 1.2 |
| 350-362 | 1.62 |
| 362-385 | 1.96 |
| 410 | 6.1 |
| 350 | 1.93 |
| 400 | 5.1 |
| 449 | 9.5 |
| 548 | 20.3 |
| 647 | 35.2 |
| 696 | 39.1 |
| 744 | 47.8 |
| 793 | 60.2 |
| 840 | 65.1 |