A method for the manufacture of crystal water-free iron(II) orthophosphate of the general formula Fe3(PO4)2 or crystal water-free iron(II) metal orthophosphate, iron(II) metal pyrophosphate or iron(II) metal metaphosphate of the general formula FeaMetb(POc)d, where a is a number from 1 to 5, b is a number from >0 to 5, c is a number from 2.5 to 5, d is a number from 0.5 to 3 and Met represents one or more metals selected from the group consisting of K, Rb, Cs, Mg, Ca, Sr, Ba, the transition metals (d block), in particular Sc, Y, La, Ti, Zr, Hf, Nb, Ta, Cr, Mo, W, Mn, Cu, Zn and the metals and semimetals of the third, fourth and fifth main groups, in particular B, Al, Ga, In, Si, Sn, Sb, Bi and the lanthanoids.