In the present work, the reaction routes for the formation of the adamantane H4Ge4S10 and double decker H2Ge4S9 thiogermanic acids have been investigated for gaseous H,S reactions with GeS2 and GeO2. H4Ge4S10 was shown to form from both GeS2 and GeO2. The synthesis route for the H4Ge4S10 phase using GeO2 as a precursor was found to be H2S(g) pressure-dependent. While H2Ge4S9 did not form from gaseous H,S reactions with GeS2 it formed readily with GeO2 reactions. In addition, the role of water in the reaction process was examined. Structural characterizations of these materials have been carried out using IR and Raman spectroscopies and powder XRD. (C) 2004 Elsevier B.V. All rights reserved.