Solid molar volumes of interest to supercritical extraction were measured for a number of alkaloids, spices, and other substances at 298 K with a gas buoyancy technique. The values obtained were 240.2 cm3/mol, atropine; 288.1 cm3/mol, berberine hydrochloride hydrate; 320.2 cm3/mol, brucine dihydrate; 289.8 cmS/mol, capsaicin; 893.0 cm3/mol, ergotamine tartrate dihydrats, 109.9 cmVmol, naphthalene; 243.2 cmVmol, penicillin V; 226.4 cmVmol, piperine; 253.0 cm3/mol, quinine; 242.0 cm3/mol, strychnine; 120.5 cm3/mol, theobromine; 123.7 cmYmol, theophylline; and 296.8 cm3/mol, yohimbine hydrochloride. The group contribution method of Fedora was used to predict the solid molar volume data. It was found that Fedora' method generally underestimated the solid molar volumes but could predict the data to within h11%.