Structure of fluorescein dipropionate acetone solvate

3-Oxospiro[isobenzofuran-1(3H),9'-[9H]-xanthene]-3',6'-diyl dipropionate-acetone (2/1), C26-H20O7 .cntdot. 1/2C3H6O, Mr = 473.38, monoclinic, P2/c, a = 14.917 (3), b = 11.964 (2), c = 13.633 (3) .ANG., .beta. = 101.98 (5).degree., V = 2380.0 .ANG.3, Z = 4, Dx = 1.321 g cm-3, .lambda.(Cu K.alpha.) = 1.5418 .ANG., .mu. = 7.93 cm-1, T = 298 K, F(000) = 992, R = 0.0556 for 2587 unique observed reflections. The title compound was prepared by esterification of fluorescein and on recrystallization from acetone it formed a crystalline inclusion compound with the solvent in the molar ratio 2:1.