Abstract: By means of potentiometric, spectrophotometric and magnetochemical methods, the sorbitol-citric acid-Fe (Ⅲ) system was studied to clarify the mechanism of action of sorbitol on the inhibition of hydrolytic precipitation of ferric ion. The experimental results show that sorbitol did not coordinate with ferric ion but stopped the hydrolytic process at the oligomerie stage, in which, mono—or bi-nuclear species were present. This effect is in' favour of the formation of stable binuclear complexes of citric acid and makes the preparations more stable.