`::Thanks for the explanation, Rabbiz.  I imagine that any serious scientist is mathematically competent enough to plug the error margins (variances) of their measurements through the math and translate them into an error margin of the result/prediction.  In the example you provided, that amounts to simple multiplying the margin of error in voltage by 10 (the ratio of voltage to heat) Again, I can't imagine why anyone would use voltages that low.  When someone is trying to study effects of a phenomena (such as electrolysis) to high precision, they generally try to get as much of the phenomena to occur as possible (while keeping certain parameters in certain rages and keeping it controlled and safe), so that they can get the most precision out of their measurement devices, as well as having the law of large numbers in their favor.    ::you go on to suggest a ``very realistic`` ratio of measurement error of heat to total electric energy input.  I don't see how the accuracy of the calorimeter would at all be correlated with the amount of electrical energy being put into the system that it's measuring (assuming there's negligible crosstalk between the circuit that's supplying electricity to the calorimeter and the circuit that's supplying electricity to the electrolysis cell).  It seems much more reasonable to me that the calorimeter's accuracy would be sensitive to the average temperature of the system, it's physical placement with-in the system, whether it's a closed or open cell, the specific heat of the solution, etc.  ::Regarding faraday efficiency, again, the faraday efficiency of water is usually very close to 100%, only rarely (shedki, for example) have faraday efficiencies significantly lower than this been reported, and that was using a nickel cathode.  Furthermore, pcarbonn has already pointed out that some experiments have measured faraday efficiency while the experiment was running on took it into account, and the results were basically the same.   In science, hypothesises are proved or disproved by experiments, and in these experiment that hypothesis was disproved.  ::Re: ``By the way, increasing the electrolysis voltage leads to a very large increase in the calorimetry errors.``  again, heat and electricity are two very different types of energy, and consequently do not impose significant measurement errors on each other.  If you increase the voltage, you increase the amount of excess heat, and thus decrease the amount of precision loss in your measurement; i.e. it is easier to tell the difference between a 10 degree vs. 20 degree temperature difference, than a .1 degree vs. .2 degree temperature difference, quite irrespective of any voltage gradients in the source material.    `