22 ELECTROLYSIS. 



Numerous and precise experiments have established that 

 this law could in every case be verified; whether the heat 

 be in a sensible form in a calorimeter, or in the form of chemical 

 energy in an electrolyte. 



Combined with Ohm's law, Joule's law can be expressed in 

 the two following formulae : 



,, E C t Wt 



H = -- and H = rs , 



E being the electromotive force of the current. 



We have already seen that the work due to a current is 

 equal to the square of the amperes multiplied by the resistance 

 and divided by 9 '81. 



Estimating, by means of Joule's law, the work absorbed by 

 a given resistance, the same formula will naturally be arrived 

 at ; let us take first the general equation : 



TT C 2 K* , 



H = calories. 



Work being equal to the number of calories multiplied by 

 the mechanical equivalent of heat, 



W = HA = C 2 IU 



Expressing the intensities in amperes, the electromotive 

 forces in volts, and the resistances in ohms, units which are 

 based on the mass and not on the weights, the formula becomes 



C* T? 

 W = Q TQI kilogrammetres per second. 



y * oi 



WORK REQUIRED IN ELECTROLYSIS. The dynamic work 

 required for decomposing a given solution is equal to at least 

 that which corresponds to the heat produced by the decomposed 

 substances when recombining together in order to reconstitute 

 the original solution. This law, which is based on the principle 

 of the conservation of energy, is often difficult to verify, owing 

 to the complex secondary actions which escape the notice of 

 even the most clever experimenters ; but it is indisputable and 

 must serve as a basis in every calculation relating to electro- 

 chemistry. 



If it were possible to decompose substances which on recom- 



