Triferro phosphide, Fe₃P

Triferro phosphide, Fe₃P, occurs as crystals embedded in a eutectic mixture of this phosphide and iron when phosphorus and iron containing more than 84.4 per cent, of iron are fused together. Its density is 6.74, and melting-point 1110° C. It dissolves in concentrated aqueous hydrogen chloride, evolving pure hydrogen. Thus: -

Fe₃P + 6HCl + 4H₂O = 3FeCl₂ + H₃PO₄ + 11H.

Triferro phosphide has been found in a cavity of pig iron from a blast furnace near Middlesbrough, in the form of small tin-white needles, strongly magnetic and lustrous. The crystals belong to the sphenoidal-hemihedral class of the tetragonal system, with the ratio

a: c = 1: 0.3469.

Save for the absence of nickel the crystals are identical with rhabdite.