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 resultprediction  In the example you provided that amounts to simple multiplying the margin of error in voltage by  the ratio of voltage to heat Again I cant 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 dont see how the accuracy of the calorimeter would at all be correlated with the amount of electrical energy being put into the system that its measuring assuming theres negligible crosstalk between the circuit thats supplying electricity to the calorimeter and the circuit thats supplying electricity to the electrolysis cell  It seems much more reasonable to me that the calorimeters accuracy would be sensitive to the average temperature of the system its physical placement within the system whether its 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  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 ie it is easier to tell the difference between a  degree vs  degree temperature difference than a  degree vs  degree temperature difference quite irrespective of any voltage gradients in the source material