NO. 2 



HISTORY OF ELECTRIC LIGHT SCHROEDER 



II 



sulphuric acid on the zinc, combined with the dissolved copper sul- 

 phate, formed sulphuric acid and metallic copper. The latter was 

 deposited on the copper cylinder which acted as the other electrode. 

 Thus the copper sulphate acted as a depolarizer. 

 The chemical reactions in this cell are, 



In inner porous jar: Zn + H2S04 = ZnS04 + H2 

 In outer glass jar: H2 + CuS04 = H2S04 + Cu 



This cell had an open circuit voltage of a little over one volt. Later 

 the porous cup was dispensed with, the two liquids being kept apart 



Grove's Cell, 1838. 



This consisted of zinc, sulphuric acid, nitric acid and platinum. 

 It made a very powerful battery. The nitric acid is called the depolar- 

 izer as it absorbs the hydrogen gas formed, thus improving the oper- 

 ating voltage. 



by the difference of their specific gravities. This was known as the 

 Gravity cell, and for years was used in telegraphy. 



grove's BATTERY 



Sir William Robert Grove, an English Judge and scientist, invented 

 a cell in 1838 consisting of a platinum electrode in strong nitric acid 

 in a porous earthenware jar. This jar was put in dilute sulphuric acid 

 in a glass jar in which there was an amalgated zinc plate for the 

 other electrode. This had an open circuit voltage of about 1.9 volts. 

 The porous jar was used to prevent the nitric acid from attacking the 

 zinc. The nitric acid was used for the purpose of combining with the 



