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Claims do not come much more controversial than the idea that water
might retain a memory of substances once dissolved in it. The notion is
central to homeopathy, which treats patients with samples so dilute they
are unlikely to contain a single molecule of the active compound, but it
is generally ridiculed by scientists.
Holding such a heretical view famously cost one of France's top allergy
researchers, Jacques Benveniste, his funding, labs and reputation after
his findings were discredited in 1988.
Yet a paper is about to be published in the reputable journal
Physica A claiming to show that even though they should be
identical, the structure of hydrogen bonds in pure water is very different
from that in homeopathic dilutions of salt solutions. Could it be time to
take the "memory" of water seriously?
The paper's author, Swiss chemist Louis Rey, is using
thermoluminescence to study the structure of solids. The technique
involves bathing a chilled sample with radiation. When the sample is
warmed up, the stored energy is released as light in a pattern that
reflects the atomic structure of the sample.
Twin peaks
When Rey used the method on ice he saw two peaks of light, at
temperatures of around 120 K and 170 K. Rey wanted to test the idea,
suggested by other researchers, that the 170 K peak reflects the pattern
of hydrogen bonds within the ice. In his experiments he used heavy water
(which contains the heavy hydrogen isotope deuterium), because it has
stronger hydrogen bonds than normal water.
After studying pure samples, Rey
looked at solutions of lithium chloride and sodium chloride. Lithium
chloride destroys hydrogen bonds, as does sodium chloride, but to a lesser
extent. Sure enough, the peak was smaller for a solution of sodium
chloride, and disappeared completely for a lithium chloride solution.
Aware of homeopaths' claims that patterns of hydrogen bonds can survive
successive dilutions, Rey decided to test samples that had been diluted
down to a notional 10-30 grams per cubic centimetre - way
beyond the point when any ions of the original substance could remain. "We
thought it would be of interest to challenge the theory," he says.
Each dilution was made according to a strict protocol, and vigorously
stirred at each stage, as homeopaths do. When Rey compared the
ultra-dilute lithium and sodium chloride solutions with pure water that
had been through the same process, the difference in their
thermoluminescence peaks compared with pure water was still there (see
graph).
"Much to our surprise, the thermoluminescence glows of the three
systems were substantially different," he says. He believes the result
proves that the networks of hydrogen bonds in the samples were
different.
Phase transition
Martin Chaplin from London's South Bank University, an expert on water
and hydrogen bonding, is not so sure. "Rey's rationale for water memory
seems most unlikely," he says. "Most hydrogen bonding in liquid water
rearranges when it freezes."
He points out that the two thermoluminescence peaks Rey observed occur
around the temperatures where ice is known to undergo transitions between
different phases. He suggests that tiny amounts of impurities in the
samples, perhaps due to inefficient mixing, could be getting concentrated
at the boundaries between different phases in the ice and causing the
changes in thermoluminescence.
But thermoluminescence expert Raphael Visocekas from the Denis Diderot
University of Paris, who watched Rey carry out some of his experiments,
says he is convinced. "The experiments showed a very nice
reproducibility," he told New Scientist. "It is trustworthy
physics." He see no reason why patterns of hydrogen bonds in the liquid
samples should not survive freezing and affect the molecular arrangement
of the ice.
After his own experience, Benveniste advises caution. "This is
interesting work, but Rey's experiments were not blinded and although he
says the work is reproducible, he doesn't say how many experiments he
did," he says. "As I know to my cost, this is such a controversial field,
it is mandatory to be as foolproof as possible." | 
