Chemical Affinity in terms of Electromotive Force. 253 



sulphate and zinc sulphate may be applied by means of the 

 above formula. Thus with copper sulphate the following 

 numbers were obtained, a battery of 4 Daniell cells being 

 used : — 



Mean tan a. 



Mean tan /3. 



Gramme of cop- 

 per deposited. 



Rise of thermo- 

 meter. 



3-4006 

 37510 

 3-8538 

 3-8084 



07275 

 0-7535 

 0-7650 

 0-7968 



0-5686 

 05777 

 0-5881 

 0-6153 



20-4 

 19-4 

 19-45 

 17-4 



Average 



3-7035 



0-7607 0-5874 



Correction for radiation 



19-162 

 -0-049 



19-113 



In these experiments the water-equivalent of the calorimeter 

 was 1179'2, whence 



£ = 963-99, 



and the E.M.F. representing the total chemical and physical 

 changes is 



3-7035-0*7607 . 1 1rt 1A8 963-99 x 31-75 xvJ 

 3 . 7035 x4x 1-10x10* Q-5874 ' 



or 



1-198 x 10 8 + 10 8 C.G.S. units or 1-198 volt. 

 With zinc sulphate the following numbers were obtained, a 

 battery of 7 Daniell cells being used : — 



Mean tan , 



tantf. 



Gramme of zinc 

 deposited. 



Rise of thermo- 

 meter. 



3-5500 

 40133 

 3-8356 

 3-9025 



0-7167 

 0-7092 

 0-7573 

 0-7548 



0-5797 

 0-5647 

 0-6010 

 0-5991 



32-2 

 300 

 31-3 

 30-5 



Average 



3-8254 



0-7345 0-5861 31-0 



Correction for radiation ... — 0*016 



30-984 



In these experiments the water-equivalent of the calorimeter 



w T as 1180*9, whence 



A = 1565, 



and the E.M.F. to be found is 



3-8254-0-7345 _ , 1A 1A8 1565x32-5xvJ 

 x 7 x 1-10 x 10 8 nKQg-i — > 



3-8254 



or 



2-395 x 10* C.G.S. units, = 2-395 volts, 

 Phil. Mag. S. 5. Vol. 9. No, 56, April 1880. 



