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When the concentration of acid rises above 62.5% the freezing-point increases, reaching 21°C by 85% H 3 PO 4 (w/w; the monohydrate). Beyond this the phase diagram becomes complicated, with significant local maxima and minima.
This is a list of the various reported boiling points for the elements, with recommended values to be used elsewhere on Wikipedia. For broader coverage of this topic, see Boiling point . Boiling points, Master List format
6 Αυγ 2020 · Boiling point: 485 K or 212 °C Melting point: 315.5 K or 42.35 °C (of crystalline solid) Dynamic viscosity: 2.4 to 9.4 centipoise (85% aqueous solution) Density: 1.83 g/cm 3 (solid); 1.68 g/cm 3 (85% aqueous solution at 25 °C) Structure. The H 3 PO 4 Lewis structure. The H 3 PO 4 compound has a total of 32 valence electrons. Since Phosphorus ...
Quantity Value Units Method Reference Comment; Δ f H° liquid-1271.66: kJ/mol: Review: Chase, 1998: Data last reviewed in December, 1971: Quantity Value Units Method Reference
Boiling Point: 158 C (85% aq) Density: 1.685 g/mL (85% aq) The most common form of phosphoric acid (H3PO4) is the 85% aqueous form. Pure anhydrous phosphoric acid is a white solid with a melting point of 42 C. Phosphoric acid has three pKa values covering a wide range (pKa's: 2.15, 7.20, 12.32).
Figure 4 (right) is an isocorrosion chart(2) for type 316L stainless steel showing the corrosion rate for various concentrations at various temperatures. Fiberglass reinforced polyester is also a corrosion resistant and cost effective material for phosphoric acid (HF free) but only at ambient temperatures.
Concentrated solutions of H3PO4(aq) are used as electrolytes in fuel cells operating typically at temperatures from 425 to 550 K. Phosphate ions, as water softeners and buffering agents, can be present in power cycles where temperatures may reach beyond the critical point of water.
