Scale-invariant power law and fractality for molecular weights

The fractal ideas of Mandelbrot are extended to the systematics of molecular weights of chemical compounds. A scale-invariant power law for molecular weights is introduced and exemplified for a randomly selected set of molecules and their dependence on effective molecular number. It is also shown that the isotopic composition of chemical compounds is characterized by a fractal pattern, which extends over the range of more than two orders of magnitude.