P&F advocated open systems for calorimetry, which opens one up to evaporation. If the water evaporates away (or is electrolyzed away) then the thermal mass reduces, and a watt of heat would produce more temperature rise at the end of the experiment than at the beginning. This may not apply to Lewis’s system, but then again it might. It certainly applies to some of the P&F systems, because they advocated open systems.
I will have to check on that. In the meantime, it seems very unlikely that 2 of the most prominent elecrochemists would have made mistakes that are basically 4 orders of magnitude incorrect. Have you ever heard of such a thing? I haven’t. When I was in engineering school, if you were off by 1 order of magnitude, you were wrong. It’s not quite believable that distinguished scientists would be off by 4 orders of magnitude. How do you account for that? How do you account for the fact that this effect has been replicated more than 14,000 times? If they were so far off by 4 orders of magnitude, surely it would have NEVER been replicated.
The P & F cells were re-filled daily. Your criticism thus does not apply. Other researchers replicated the P & F results with open cells, though not CalTech, MIT, and Harwell.