You said CaO reacts with water. How about hydrogen all by itself? Not H2O.
I actually said:
I was wondering if a similar but smaller reaction would occur with plain hydrogen.
Maybe the chemists here can comment, as information on the monohydrate reaction seems well hidden, across the internet, by all the references to calcium (II) hydrate.
In other words, I know the monohydrate exists (CaOH) but could not find a reference to reactions between plain hydrogen (either monatomic or H2) with CaO. For all I know, it might not occur - or it might only occur if the CaO granules are very finely divided (which might be extra support for Ed's observed "particle size threshold effect").
I think it very unlikely that CaO would react chemically with hydrogen alone. Worth pointing out that Johnson Matthey's 'Harlow Metals' subdivision who produced a fair amount of JM's pure Pd up until the early 1990's much of it from jewellery and a very large cache of un-circulated french Pd coins brought over by the Free French in WW2 used Barium metal powder as an oxygen getter in their artisanal refining process. This produces BaO, a very similar basic oxide to CaO. I have often wondered if the variability of the Ba dosing was the reason some JM Pd worked, and some did not.
Barium oxide, BaO, is a typical basic oxide. It is more basic than the oxides of other alkaline earth metals like magnesium, calcium and strontium.
It reacts with water to form barium hydroxide, a strong base.
BaO + H2O → Ba(OH)2
I have often wondered if the variability of the Ba dosing was the reason some JM Pd worked, and some did not.
Back when I was looking at the problem of hydrogen embrittlement in alloy steels (e.g. plated high tensile bolts), I did think about "cleanliness" and the presence of solid impurities that might act as hydrogen "centres of migration". Aluminium is often used to "kill" steel (grab oxygen), and some small aluminium oxide particles remain in the melt.
I was always intrigued by the time delay between the torque tightening of a hydrogen-loaded bolt (say, to 2/3 of yield stress) and the sudden fracture of the bolt. Usually the fracture happened overnight, so nobody saw it happen - and you just found a bolt-head on the floor in the morning.
The classic view is that the time delay allows hydrogen to migrate to grain boundaries and lattice dislocations - where it builds up pressure, and allows cracks to form. However, when inspecting the surface of the fracture there never seemed to be any evidence of particular crack origins. (Unlike when inspecting, say, the aftermath of a fatigue fracture). The surface was always nicely granular - as if it had been fractured by a sudden tensile overload.
My suspicion was that there was some kind of sudden physical change in the region of highest stress - leading to the fracture. Maybe the changes centred on impurities, rather than simple dislocations. Some metal oxides can act as catalysts, after all.
Maybe the changes centred on impurities, rather than simple dislocations. Some metal oxides can act as catalysts, after all.
If one(or many) had enough Pd and time, both of which are limited resources
as well as deuterium and suitable calorimeter./electrolysis/heater setup
then one (or many) could test a range of impurities CaO, BaO. SiO2... silicates,,,etc
of different hardness,shapes, sizes,
but initially it would be sensible to replicate Storms results with Pd +sub35micron CaO
unfortunately I am not in a position to do that at this time.