The dissolution of silicon in aqueous solutions was investigated by etching and electrochemical measurements. At high ratios, etching occurs via an electroless process in which reduction of Cr (VI) and oxidation of Si take place simultaneously. A model is presented for the anodic dissolution of silicon in solutions. The electrochemical results have been used to determine the relevant rate constants for the different reaction steps. Combining cathodic and anodic processes resulted in a rate law for the etching kinetics. Good agreement was obtained between calculated and measured etch rates.