Water memory

Water memory is the disputed claim that water retains a lasting imprint of substances previously dissolved in it after those substances are removed. It is often invoked to explain homeopathy.

Hydrogen bond: An attraction between a hydrogen atom bonded to an electronegative atom and another electronegative atom. Water-memory proposals often attribute persistence to networks of these intermolecular attractions.
Homeopathy: A system of alternative medicine based on highly diluted preparations and the principle of like cures like. Water memory is commonly offered as a physical explanation for homeopathic preparations diluted beyond molecular presence.
Avogadro constant: The number of specified particles in one mole, exactly 6.02214076 × 10²³. Beyond ordinary dilution limits, preparations are expected to contain no molecules of the starting substance.
Scientific skepticism: The practice of evaluating claims through critical inquiry and evidence proportionate to their strength. The dispute illustrates why extraordinary claims require rigorous testing and independent replication.
Water structure: The spatial arrangement and interactions of molecules in liquid water. The claim requires a distinctive structure to outlast the dissolved substance.
Jacques Benveniste: A French immunologist whose research and public claims about highly diluted solutions became controversial. His laboratory reported biological activity in solutions alleged to retain water memory.
Molecular diffusion: The net movement of particles from regions of higher concentration to lower concentration. Diffusion and molecular collisions continually redistribute dissolved substances and solvent molecules.
Peer review: Evaluation of scholarly work by experts before or after publication. Publication of the contested study raised questions about what peer review can establish.
Hydrogen-bond dynamics: The formation and breaking of hydrogen bonds over time in molecules and liquids. Rapid rearrangement of water’s hydrogen bonds challenges long-lived molecular imprints.
Démystification Commission: A team that investigated Jacques Benveniste’s reported high-dilution experiment in 1988. Its blinded retest failed to reproduce the effect under controlled observation.

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Fringe scienceBroader topic: The proposal conflicts with established chemistry and has not gained reliable experimental support.