Abstract <p>The process of formation of palladium hydroxo complexes during hydrolysis of palladium chloride in an alkaline medium was investigated by the in situ small-angle X-ray scattering (SAXS) technique. It was shown that the aging process of palladium hydroxo complexes corresponded to the Ostwald ripening mechanism. The time dependent particle shapes and particle size distributions were determined for the palladium hydroxo complexes in solution. It was found that loose particles described by the form factor of Gaussian chains were formed in the solution at the beginning of the aging process. After they reached a certain size, the process of chain folding and transformation into particles with a compact shape took place. Further, compact particles aggregated to form larger secondary aggregates.</p>