As you may have figured out by now, "constantan" is a copper-nickel alloy of unusual properties, whose main feature is its constant resistivity over a wide range of temperatures. "Constant" being the operative eponym.
In addition to the high catalytic energy, it is fair to ask: what is it about this alloy which sets it apart for other good spillover catalysts? Constancy. Doh! . as in coherence. Think about it - catalysis is due to surface near-field effects at the angstrom level. With 99 % of all catalysts, this ability changes with variations in temperature, due to changes in resistivity and the follow-on changes in the near-field as seen by an approaching H2 molecule. However, in one unique case - once you have stabilized this special alloy and hydrogen into a 'groove' (or temperature spectrum) then you have an increasing flow of spillover, which is exponentially to a much higher level with positive feedback . whereas with other alloys the decrease in conductivity with temperature and the desired effect is self-quenching at a low level. It is bizarre to think that an emergent property and even a 'critical mass' property could materialize in an intangible characteristic as mundane as "constant resistance over a wide range of temperatures". This property of constantan could be worded better. I hope it is clear to those who are especially interested in replicating Rossi. Jones
