It is shown that alkylchlorostannanes can be successfully used for synthesis of chemically modified silica. The hydrolytic stability of the materials obtained is studied. It is revealed that grafted layers of Et3SnCl and Et2SnCl2 can be removed at pH values lower than 4, whereas silica modification with EtSnCl3 produces layers that are stable at pH values 0-7. Mossbauer spectroscopy of the samples obtained was done; parameters of the spectra are determined. It is found that rigidity of attachment of tin atoms strongly increases in passing from Et3SnCl to Et2SnCl2 and, further, to EtSnCl3