Comment on “The defining role of structure (including epitaxy) in the plausibility of homeopathy”

Sir,

We wish to draw attention to serious anomalies and incongruities in the UV absorption data presented in the paper by Rao et al, published in the July 2007 issue of Homeopathy.[ ¹ ] In a study of this nature, which examines multiple samples of ethanol, there must be absolute uniformity in the source of the solvent. For the data to be valid, all ethanol used must be sourced from the same stock bottle. However, the authors fail to mention of this point, and it is clear from the results presented that the source of ethanol in this investigation was not uniform.

The most striking anomaly is the UV spectrum presented for “plain ethanol”, a single trace repeated three times in Figure 3 of Rao et al. (p. 179). The provenance of this sample is not recorded. This trace reveals extremely high absorbance (greater than 0.8 absorbance units) at 250 nm, falling off steeply towards 400 nm but still above 0.4 units by 350 nm, and demonstrating an absorbance peak of 0.65 units with a lambda-max of about 330 nm. It is impossible to represent this trace as being ethanol of any recognised degree of purity. Spectroscopic grade ethanol has an absorbance of less than 0.05 units between 250 and 400 nm,[ ² ] and even USP/NF pharmaceutical grade ethanol has an absorbance of less than 0.3 units at 250 nm, falling off to less than 0.1 units by 270 nm.[ ³ ] If the substance measured by the authors as “plain ethanol” was indeed ethanol at all, it is clear that it contained extremely high levels of impurities, possibly including acetone.

In contrast, the spectra of the samples which were diluted and succussed (Nat mur, Nux vomica and the “succussed ethanol” with no mother tincture), and which were presumably all supplied by Hahnemann Laboratories, demonstrate substantially lower levels of impurities. While still not being spectroscopic grade ethanol, these samples could well represent ordinary pharmaceutical grade ethanol. The authors claim these samples are “different”, however the evidence presented for this is weak to nonexistent.

Figure 1 presents one trace each for Nat mur and Nux vomica, each at 6c, 12c and 30c potencies. The traces are said to be “representative”, however with no information on repeatability or how the “representative” traces were selected, it is impossible to say whether there is any real difference between any of the six spectra.

Figure 2 purports to address this point, but fails to present the necessary data. The legend declares that 10 samples of each of the six remedy preparations were analysed. The accepted way to present such data would be as mean absorbance ± standard deviation for each wavelength point, or at least for a representative selection of wave length points. Statistical analysis could then be used to demonstrate whether or not there was a real difference between any of the remedies or potencies. However, the authors have instead chosen to present only two traces for each preparation, as “envelopes of differences”. The derivation of these traces is not explained, although we surmise that “extreme” high and low traces for each preparation were chosen to provide an impression of the range of results obtained. This is not an appropriate method of handling data of this nature, as most of the information is lost and statistical analysis is rendered impossible.

A further difficulty with Figure 2 is that the upper (open circles) trace in the top graph of Figure 2a (30c Nat mur) appears to be a duplicate of the upper (filled circles) trace in the top graph of Figure 2b (30c Nux vom). Comparison with other traces of the two remedies indicates that this trace is really one of Nux vom, which has been duplicated into the Nat mur graph in error. In conclusion, paucity of data, ambiguity of presentation and lack of statistical analysis prevent any conclusions being drawn from the information in Figure 2.

Comparison of Figure 2 with Figure 1 reveals that all six traces presented in Figure 1 are taken from Figure 2, in each case the filled-circles traces. If indeed the traces in Figure 2 represent the extreme range of results obtained, this is startling, as the traces in Figure 1 are stated to be “representative”. In addition, while it does appear that the Nux vom samples tended to demonstrate higher absorbances than the Nat mur samples (excluding the obvious mistake noted above), in two out of the three potencies the higher Nux vom trace from Figure 2 has been chosen for inclusion in Figure 1, thus exaggerating the apparent difference.

Figure 3(b) and (c) again repeats the same six traces as Figure 1, this time grouped by remedy. Presented in this way, it is clear that there is absolutely no difference between the three potencies of Nat mur, and that while variation between the Nux vom potencies is a little more pronounced, again all three appear to come from the same population. The same is true of the three potencies of “succussed ethanol” presented in Figure 3a.

On visual inspection it does appear that there may be genuine differences between the three remedies (although no statistics are presented to allow this to be tested), with the Nat mur showing the lowest absorption and the Nux vom the highest, with the succussed ethanol lying somewhere between. Nevertheless, these differences are entirely consistent with small differences in purity of the ethanol stock used for preparation of the three remedies—small, that is, relative to the very high level of impurity evident in the “plain ethanol” sample presented alongside. This degree of variation in UV absorbance is entirely to be expected between different batches of pharmaceutical grade ethanol, which is not prepared with spectroscopic analysis in mind. The authors make no mention of having stipulated to Hahnemann Laboratories that all material sent to them should be prepared from the same stock bottle, and the data presented indicate that the different remedies, possibly prepared at different times, simply came from different bottles of ethanol.

It is clear that the data presented are wholly inadequate to support the authors’ assertion that UV spectroscopy can differentiate between the two remedies, and between different potencies of the remedies. If the authors wish to test their assertion it will be necessary to repeat the work from the beginning, ensuring that all samples used in the study are sourced from the same bottle of stock solvent, that all duplicate preparations for precision assessment are separately prepared de novo from the mother tinctures, and that sufficient data are generated to allow robust and valid statistical analysis of the results.

• References

• 1 Rao M.L., Roy R., Bell I.R., Hoover R. The defining role of structure (including epitaxy) in the plausibility of homeopathy. Homeopathy 2007; 96: 175-182.
• 2 Sigma Aldrich catalogue, ACS spectrophotometric grade ethanol 95.0%, at ⟨ www.sigmaaldrich.com/catalog/search/ProductDetail/SIAL/493511⟩.
• 3 Sigma Aldrich catalogue, USP/NF grade ethanol 190 proof, at ⟨ www.sigmaaldrich.com/catalog/search/ProductDetail/ALDRICH/493538⟩.