The structure of the aggregates formed by partial hydrolysis of Pe-PO4 solutions was investigated at the semilocal scale by small angle X-ray scattering. Aging has no effect on the structure of Fe-PO4 colloids, except for a P/Fe molar ratio of 0.2 and an hydrolysis ratio R = 1.0 where aggregation of the aggregates (approximately 100 Angstrom) increases from 2.30 to 2.85 with increasing R. For P/Fe = 0.5, larger and more open aggregates are formed and the hydrolysis ratio has little influence on the semilocal structure. The P-Fe distance and the initial stoichoimetry control the structure of the resulting aggregates.