  Magnetic susceptibility and specific heat versus temperature measurements on
polycrystalline samples of Sr3Cr2O8 and the isostructural, nonmagnetic compound
Sr3V2O8 are reported. A Curie-Wiess fit to the high-temperature susceptibility
data for Sr3Cr2O8 indicates that the Cr atoms are in the rare Cr^5+ (Spin S =
1/2) valence state as expected from the composition. The ground state was found
to be a spin singlet with an excitation gap Delta/k_ B = 61.9(1) K to the
magnetic triplet states, and a weak interdimer coupling of 6(2) K was inferred.
The specific heat and susceptibility measurements on Sr3V2O8 reveal a phase
transition at 110 K which is evidently a structural transition.
