We investigated the chemical reactivities of (La0.7Sr0.2Ba0.1)ScO3-delta (LSBS) and LaScO3 powders and Pt foil as functions of reaction temperature, T, oxygen partial pressure, P(O-2), and reaction time, t. The LSBS powder showed a maximal Pt content of ca. 33 mg (ca. 3 wt %) under the conditions T = 1573 K, P(O-2) = 0.21 atm (in air), and t = 10 h. Subsequent heat treatment at 1773 K in air for 10 h resulted in the deposition of Pt fine particles (1.7 mg) on the LSBS powder and a weight gain of the Pt foil (4.3 mg).