I have also seen concentrated sulphuric acid being used, but what makes phosphoric acid preferable to sulfuric acid?
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5$\begingroup$ Sulphuric acid can also act as an oxidant, phosphoric cannot. $\endgroup$ – Waylander Jan 31 '19 at 18:52
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$\begingroup$ Ohh, thanks! Also, does the concentration of acid matter? $\endgroup$ – Aabesh Ghosh Jan 31 '19 at 18:56
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3$\begingroup$ Phosphoric acid is most often used as polyphosphoric acid which is a thick syrup. This is essentially neat phosphoric acid, which can be made stronger by addition of P2O5. $\endgroup$ – Waylander Jan 31 '19 at 19:13