Molecules Clump on Dilution
A surprising discovery that molecules dissolved in water clump together when the solution is diluted is said to explain homeopathy. Dr. Mae-Wan Ho explains why the result flies in the face of conventional chemistry.
Two chemists from the Kwangju Institute of Science and Technology in South Korea made news last year [1]. Their surprising discovery that molecules dissolved in water clump together was reported in the New Scientist and the popular media as a possible explanation of why homeopathy works.
The obvious 'explanation' is that some dilute solutions may have more molecules in it than expected, perhaps even at dilutions beyond the point at which any molecule could be left in solution. But if some parts of a solution contain more molecules than expected, other parts would contain less, so most of the time, homeopathy should not work at all. And that, indeed, is the conventional wisdom of the medical establishment.
The researchers themselves were surprised by the suggestion that their work had any relevance to homeopathy. However, the finding itself has significance far beyond its applicability to homeopathy.
The investigations started on a class of chemical substances known as cyclodextrins (DC), which, when combined with non-polar molecules (molecules without electrical charge), enable the latter to dissolve in water. They make a complex of ß-cyclodextrin with [60]fullerene, more popularly known as Buckyball, or Buckminster fullerene, in honour of architect/polymath Buckminster Fuller, who invented the shape as a geodesic dome. These complexes were found to form clusters in water.
But then scientists found that a wide range of other substances such as salts and polymers also form clusters in solution.
The new discovery made by the South Korean researchers is that cluster size increased steadily with increasing dilution in water. In contrast, no clustering of the molecules occurs in organic solvents. They found the same behaviour for cyclodextrin-fullerene complex, ß-cyclodextrin by itself, sodium chloride, disodium guanosine monophosphate and a DNA oligonucleotide.
Using the technique of laser light scattering, it was possible to estimate the size of size of ß-cyclodextrin clusters. The diameter of the clusters increased from 0.55 µm at a starting concentration of 0.216 mM to 3.255 µm at 0.01mM. The clusters were confirmed by scanning electron microscopy after the solutions were dried.
Interestingly, when the starting concentration was 14.27mM and diluted down to 0.3524mM, cluster size increased from 0.393 µm to 3.12 µm. Thus, the size of the clusters varied depending on the starting concentration.
In other words, "the solution history is an important factor in the growth dynamics of the aggregates". That was the really unexpected finding, and flies in the face of conventional linear chemistry.
For sodium chloride, a starting solution of 5.5M diluted down to 0.785M gave an increase in aggregate size from 1.491 to 4.95µm. The results were similar in all the other substances investigated. The increase in cluster size was non-linear, slow at first, and rapid at higher dilutions.
The increase in cluster size was "almost instantaneous", and remained stable at least over the next three days.
Why do these clusters form? No one knows for sure, and certainly the importance of solution history is impossible to accommodate within conventional, classical chemistry. Could it be yet another manifestation of "The strangeness of water"?.
- Samal S and Geckeler KE. Unexpected solute aggregation in water on dilution. Chem. Commun.2001, 2224-5.
