Calculates molecular weight from molecular formula, and also the mass of the compound corresponding to a selected number of millimoles. The percentage elemental composition can be displayed, and the user may also define their own groups for use in calculations.
In 1978, Omer Roucoux published this chemical jigsaw puzzle. It is available here in two parts, as a GIF and the original DrawFile version (for RISC OS), which you can download separately. Best hard copy results will be obtained from the original.