Table 3: Average composition of two industrial phosphoric acid samples.

SpeciesConcentrationMilliequivalents of solute per liter

P2O554% w/w
13.4480 g/L(−) 274.0
CaO8.4116 g/L(+) 299.9
SiO218.0240 g/L( ) (−) 1199.9
Fe2O37.9843 g/L(+) 149.9
Al2O38.1567 g/L(+) 239.9
MgO4.8364 g/L(+) 239.9
Na2O3.0989 g/L(+) 99.9
K2O3.7678 g/L(+) 79.9
HF3.4196 g/L(−) 170.9
HCl0.1773 g/L(−) 93.7

The phosphoric acid concentration is typically expressed in terms of the P2O5 concentration. The conversion formula is as follows: [H3PO4] = [P2O5] × 196/142. Thus, 54% P2O5 concentration corresponds to an acid concentration of 74.5%.