A 6x potency corresponds to a reasonably concentrated solution (i.e. it is the same as "one part per million", or a milligram of solute to 1 kg solvent-or a litre of water). I do not pretend to have any knowledge of pharmacology beyond the popular, but I believe that many drugs are administered as "ppm" solutions. 12x and 18x potencies are correspondingly less concentrated by 6 and 12 orders of magnitudes. However, even an 18x potency would have some 1,000,000 particles remaining to effect some biochemical change. At a 30x potency, there should be no particles/molecules of the original solute (it should have diminished to 1-2 particles at 24x). At 30x potency, the solution should be chemically indistinguishable from the solvent used to make the preparations.