Galvanic Pile, and Electromotive Forces. 



433 



difference between the indications of the calorimeter in the two 

 cases was consequently equal to the galvanic heat which was 

 developed in the platinum wire. The results of the different ex- 

 periments will be seen from the following Table. Column a 

 gives the length of the wire ; b, the deflection of the calorimeter 

 in heat-units (the gram being taken as unit of weight) when 

 both the pile and the platinum wire were enclosed in the 

 calorimeter ; c, the corresponding deflection when the plati- 

 num wire was excluded from the calorimeter ; b—c, the dif- 

 ference between these two deflections, or the galvanic heat de- 

 veloped in the wire ; and gw the quantity, thence obtained by 

 calculation, of the galvanic heat in the pile and the platinum 

 wire together. 



Diameter of the wire =0*265 millim. 



a. 



b. 



c. 



b-c. 



gw. 



millim. 











25 



18092 



13127 



4965 



\ 9652 

 J 



50 



18247 



11690 



6557 



100 



18185 



10439 



7746 



j 10820 



200 



18022 



8992 



9030 



In another series of experiments, in which a thinner wire 

 was used, the following results were obtained : — 



Diameter of the wire =0*175 millim. 



a. 



b. 



c. 



b-c. 



gw. 



millim. 

 50 

 50 

 100 



18082 

 18173 

 18066 



9955 

 10101 



8381 



8127 

 8072 

 9685 



1 12040 



Mean ... 



18124 







10837 



As the preceding Tables show, the value of gw increases as 

 the resistance becomes greater and therefore the current- 

 intensity less. 



According to Favre and Silbermann, there are developed, 



Heat-units, 

 in the combination of one equivalent of) 4.94.51 



zinc (33 grams) with oxygen . . J 

 in the combination of the oxide with) ini^' 



sulphuric acid J 



On the other hand, in the decomposi- \ 044™ fare con 



tion of one equivalent of. water, J \ sumed. 



Sum . . 18444 

 Phil. Magi S. 5. Vol. 3. No. 20. June 1877. 



2F 



