Talk:Cold fusion/Contrary evidence/Dash-Zhang Replication Effort
Question for Abd
This discussion was moved to Talk:Cold_fusion/Skeptical_arguments/Were_the_excess_heat_results_ever_shown_to_be_artifact?/Mist#Question for Abd --Abd 15:05, 6 January 2011 (UTC)
The moved discussion does contain specific discussion of the Zhang work and calorimetry, but my conclusion is that the objection about mist/vapor ratio has no application to the work of Dash and Zhang, nor to the replication effort by Earth Tech, because the calorimeter is not vulnerable to misting error, and calculated excess heat does not consider mist/vapor ratio at all. Only if it were considered, and lost mass were assumed to be vapor when it was mist, would misting become an error source in this work. The reasons for this conclusion are given in the moved discussion. Caprice, do you agree as to the Dash/Zhang work? Your concern about misting applies to other experimental forms and different calorimetry design.
The discussion about misting and consequences led me to a much better understanding of the Dash/Zhang results, so it may be worth reading for that. For now, my off-the-cuff summary:
Dash and Zhang appear to be seeing some significant excess heat, but only at the lowest levels considered significant. Earth Tech did not observe this heat, but the Earth Tech replication wasn't exact, and details matter; as Earth Tech was aware, sometimes even seemingly inconsequential details matter. Cold fusion results, from the Pons-Fleischmann electrochemical approach, are known to be highly variable, dependent on conditions which are imperfectly understood. Sometimes a sample of palladium will produce the effect, sometimes not, the same sample.
It's easy to understand why this makes many people skeptical, but it shouldn't be surprising. If palladium deuteride always generated excess heat, it would have been noticed many years ago. In fact, it was rare, and it took Pons and Fleischmann five years to get their work to the point where one cell out of six showed excess heat, and they were not ready to publish, the history makes that clear. They were forced to publish prematurely, by the University of Utah, for legal, patent reasons.
Modern work finds much higher percentages of active samples and cells, but it's still quirky and less than reliable; however, excess heat is statistically very significant. The Dash-Zhang work is not good evidence for it, because it's marginal, plus it uses very high temperatures, close to boiling, where calorimetry errors can be higher. Other approaches are not marginal.
A major part of Zhang's work is the study of what is different in samples that show excess heat and those that do not. His most recent reports show anomalies in the resistance of the cathode palladium, and cathode resistance is one measure of loading ratio. Apparently the excess heat phenomenon causes irreversible changes in the cathode nanostructure, his plot of temperature vs. resistance doesn't return to origin when the cathode cools, as it would without such changes (if the loading were the same). --Abd 17:26, 6 January 2011 (UTC)