352 Prof. Helmholtz on Galvanic Currents 



differently concentrated portions of the solution could be re- 

 duced to a minimum by inserting narrow connecting tubes, 

 without altering the electromotive force of the apparatus, which 

 we wish to calculate. 



We can, on account of this, neglect these two irreversible 

 processes, and apply Carnot and Clausius's law to the reversible 

 ones. Since all the bodies taking part in the process are each 

 to have the same constant temperature, no heat can be converted 

 into work, nor can any work be converted by the reversible 

 processes into heat. The sum of the work gained and lost 

 must therefore, taken by itself, be equal to nil, as must also 

 the sum of the heat withdrawn and supplied. Hence result 

 two equations. 



The one, which refers to the heat, expresses nothing but 

 what can be obtained without consideration of the electrolytic 

 process — namely, that the same amount of heat is generated 

 when the metal of the electrodes comes into a concentrated 

 salt-solution which is gradually diluted as when it enters 

 directly into the dilute solution. 



The second equation expresses that with the above-described 

 reversible process the mechanical work must be equal to nil. 

 Work is expended, partly, 



(1) for the collection of the electricity. If P ffl and P* are 

 the values of the potential-function in the anode and cathode, 

 and in the time t the electricity + E is collected in P a and 

 taken out of P&, the work for the unit of time is, as already 

 remarked, 



J(p„-p*)=j(p.-p*> 



(2) Partly, work is performed by the expanding vapour. 

 This vapour is first evolved under the pressure p, which cor- 

 responds to the degree of saturation of the liquid with salt ; it 

 then expands at a constant temperature up to the pressure p x . 

 Naming the work for the unit of mass W, and the volume of 

 the unit of mass V, both referred to the given constant tem- 

 perature, 



W=pV+( Vl p.dv (lc) 



The total quantity of this work, 2g, is found, by means of 

 the values shown in equations (1) and (1b) of the current, to 

 be equal to 



( h-.dy.dz.w{u^[_ q {l-n)-]+v^[g(\-n)-]+w^lq(l-n)] 

 — {dco. Wq(l — n) {v cos a + v cos b + w cos c } = 33$. (2) 



