We have used thermogravimetry and X-ray absorption spectroscopy to examine the water content, oxidation state, and local structure of V for V2O5.nH(2)O aerogels and ambigels in the pristine state and after heating under vacuum (100 muTorr) at 114 and 220degreesC for 25 h. On the basis of thermogravimetric analysis, the composition of the aerogels and ambigels consists of about 2 and 1 mol of H2O per mole of V2O5 in the pristine state and after heating at 114degreesC, respectively. Thermogravimetric analysis reveals the absence of loosely bound H2O in the network of the aerogels and ambigels heated at 220degreesC. Analyses of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra reveal that the oxidation state of V for aerogels and ambigels in the pristine state (V2O5.2.0H(2)O) as well as those heated at 114degreesC (V2O5.1.0H(2)O) is similar to that of V in V2O5; that is to say +5 (pentavalent V). Heat-treating the aerogels and ambigels at 114degreesC does not lead to a measurable change in the oxidation state of V. The local structure of V under these conditions is similar to that of V in orthorhombic V2O5 except for a higher degree of local symmetry within the structure of the VO5 square pyramid. Analyses of XANES and EXAFS spectra of aerogels and ambigels heated at 220degreesC, on the other hand, reveal the presence of both tetravalent and pentavalent V. The fractions of tetravalent V are estimated to be 0.29 +/- 0.08 and 0.26 +/-0.08 for the aerogels and ambigels, respectively. The mixed valency can be in the form of a single phase with a solid solution of tetravalent and pentavalent V sites or a two-phase system with one phase containing tetravalent V and the other phase containing pentavalent V.