This Indian Institute of Technology Bombay press release quotes some research papers which claims to prove that homeopathic remedies do retain original substances even when diluted.

The paper reports the fascinating observation that certain high potency (highly diluted) homeopathic remedies made from metals still contain measurable amounts of the starting material, even at extreme dilutions of 1 part in 10 raised to 400 parts (200C).  It is well known that a series of 1:99 dilutions done sequentially will produce a significant dilution of the starting material in very short order. Specifically, if the starting material is at one molar concentration (6.023x10e23 molecules per liter), then at about the 12th dilution (12C) there should be no or very nearly no molecules left of the starting material. At 200th dilution (200C) the likelihood of there being even one atom of the starting material approaches zero. However, dilution does not work so simply, according to this paper. Using electron microscopy (TEM), electron diffraction, and atomic spectroscopy, Chikramane et al. found that, contrary to the arithmetic, there are nanogram quantities of the starting material still present in these ‘high potency’ remedies in the form of nanoparticles.

This was published in a homeopathy journal and not a chemical engineering journal, although the department was chemical engineering.

A later paper, Why Extreme Dilutions Reach Non-zero Asymptotes: A Nanoparticulate Hypothesis Based on Froth Flotation suggests that nano-particles are distributed unevenly, floating to the top of the container, which may interfere with dilution predictions, public in a journal from the American Chemical Society.

However, physicochemical studies of these solutions have unequivocally established the presence of the starting raw materials in nanoparticulate form even in these extreme (super-Avogadro, >1023) dilutions. In this article, we propose and validate a hypothesis to explain how nanoparticles are retained even at such enormous dilution levels.

Another researcher in a Letter to the Editor that the original element was found may be be because those original elements were stuck to the inner walls of lab glass:

Further-more, soluble compounds can be captured by nanosized structure, often nanobubbles, lining the boron-silicate glasses with which dilutions, subjected to mechanical stresses, are made. Therefore, an imprecise fraction of compound may be dispersed into the solvent from the glass wall whenever a mechanical stress is applied to the dilution, possibly giving gelsemine concentration far from the theoretical evaluation into pure water.

(The "mechanical stress" presumably refers to the succussion during homeopathic preparation.)

In practice, are some of the original materials still found in 200C dilutions?

  • 3
    Not a dupe of water memory.
    – Sklivvz
    May 29, 2015 at 19:02
  • 1
    The papers themselves give reasons why the dilution procedure may be inaccurate/imperfect, e.g. the conditions causing a film of more-highly-concentrated material at the top of the container, which is drawn off and reused in the next dilution.
    – ChrisW
    May 30, 2015 at 13:52
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    So the real question isn't if some quantity is retained but if an experiment can evade a mathematical prediction of how much should be left. I'm always amazed that homeopathic remedies don't kill people with all the trace amounts of diluted poisons you can find in them. May 31, 2015 at 6:13
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    At 200C, the predicted concentration is not mathematically zero, but it is effectively zero; it'd be astonishing if there was a single molecule left in any 200C homeopathic medicine preparation ever made. But someone's claimed this mathematical prediction is irrelevant because in practice there are non-trivial amounts left. If that is true, most of the theoretical objections to homeopathy must be discarded (leaving only the practical objections - that it hasn't been shown to be better than placebo!) I think the title matches the claim, but I wouldn't object if it was edited.
    – Oddthinking
    Jun 1, 2015 at 8:55
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    @CandiedOrange "Do homeopaths sometimes fail at diluting?" seems appropriate.
    – DavePhD
    Jun 1, 2015 at 13:46

1 Answer 1


This Indian Institute of Technology Bombay press release quotes some research papers

This isn't really true. It is just one research paper, and one comment on said research paper. Also, it merely describes the paper, without quoting it.

In any case, a major finding of the first paper is that there are discrete metal particles in the mixture. In other words, it is not a true solution.

That there are discrete metal particles in the mixture, permits mechanisms whereby the manipulative steps one executes in diluting do not result in a quantitative dilution.

For example, if you throw 100 liters of ping-pong balls into a 1,000,000 liter swimming pool filled with water, stir the swimming pool, and skim a sample of material from the top layer of the pool, the volume-fraction of ping pong balls in the sample will differ from the ratio 1:10,000 expected on a basis of the ping-pong balls being randomly distributed in the water, because ping-pong balls float.

This is basically what the first two articles mentioned in the OP are finding. The metal particles are concentrated at the surface due to bubbles. If only material from a top layer is used for each round of dilution, the dilution is not quantitative. The final concentration is greater than would be predicted on the basis of what would happen to a true homogeneous solution.

Flotation is a long-known technique for concentrating metals such as gold at the surface of a mixture using bubbles. See Froth Flotation: A Century of Innovation.

The research cited in the OP is not something that can be generalized to all homeopathic preparations. It only applies to certain homeopathic solutions prepared in certain ways. For example, if material is not taken from near the top of the container, but instead in the central portion of the container, then the final preparation would be at least as dilute as expected.

The title question "Do extreme homeopathic dilutions still retain quantities of the starting materials?" is phrased so as to necessarily be false. If it retains a significant amount of starting material, by definition it is not extremely dilute. The articles in the OP simply show that dilution techniques that work for true solutions, such as salt water, do not always work quantitatively for mixtures with solid particles.

The above findings are further discussed in Adverse effects and homeopathy: may remedies yet contain noxious or toxic molecules? British Journal of Clinical Pharmacology 2014 Jul; 78(1):184-5. The research cited in the OP, together with research such as Effect of alcohol-water exchange and surface scanning on nanobubbles and the attraction between hydrophobic surfaces. J Colloid Interface Science 2008; 325: 267–74 is being accepted as correct and showing the possible risks of metals or other starting materials being unexpectedly present due to failed dilution attempts.

  • I don't think this answers the question. The "press release" (is it?) references two papers. If "quotes" isn't the right word, I think editing the question is more productive. The idea that floatation of nano-particles (plus pipetting only from the froth or edges) theoretically might lead to original material, but does it in practice? Sure, the "dilutions" wouldn't be true dilutions in a strict sense, but I think the term "homeopathic dilutions" clearly references an understood process, as original described by Hannemann.
    – Oddthinking
    Jun 1, 2015 at 2:35
  • @Oddthinking I suppose you mean Hahnemann. If there is an "understood process" of attempted dilution that specifies whether mixture is removed from the top vs. other parts of the volume of concentrated mixture, I am not aware of it. The press release refers to a paper and editorial note about the paper and lists both as "Homeopathy 2010; 99: 231‐242".
    – DavePhD
    Jun 1, 2015 at 9:07
  • @Oddthinking "but does it in practice?" I think that according to the referenced paper, yes: that is what the paper says has happened.
    – ChrisW
    Jun 1, 2015 at 11:35
  • @ChrisW yes, they show there are metals present in the commercially available preparations: "The homeopathic medications used for the purpose of research were obtained commercially from authorized distributors of a leading homeopathic drug manufacturer in India (SBL) and an Indian subsidiary of a multi-national homeopathic company viz. Dr. Willmar Schwabe India Pvt. Ltd. Random batch number samples were purchased from the market and no special effort was made to get samples from the company. Since we purchased these medicines from the market..."
    – DavePhD
    Jun 1, 2015 at 11:42
  • @ChrisW: Given we have a peer-reviewed article in the question, I think to answer it we need to demonstrate it has been reproduced/not reproduced, or whether it has been cited approvingly/disapprovingly, or (ideal) whether a meta-study exists.
    – Oddthinking
    Jun 1, 2015 at 11:44

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