1877.] 



Contact of different Substances. 



313 



Table showing the Difference of Potential of the Copper Terminals of 

 Voltaic Elements in which no Current has circulated. 



Composition of Element. 



Difference of Potential 

 in terms of 



Standard 

 Daniell. 



Tin in dilute sulphuric acid (1 volume of acid io 

 8 volumes of distilled water) and 



Tin in solution of caustic potash (1 part by weight 

 of caustic potash to 5 parts by weight of distilled 

 water) .' 



Tin in distilled water and 



Tin in solution of caustic potash (1 part by weight 

 of caustic potash to 5 parts by weight of distilled 

 water) 



Copper and zinc (both well cleaned) in distilled 

 water : — 



When metals are first immersed 



After immersion for 1*5 hour 



„ „ „ 3 hours . . . . 



Copper and amalgamated zinc in dilute sulphuric 

 acid (1 volume of commercial sulphuric acid to 

 8 volumes of distilled water) 



Copper in distilled water and 



Copper in solution of potassium cyanide (1 part by 

 weight of potassium cyanide to 5 parts by weight 

 of distilled water) 



Daniell : — 



Copper in saturated solution of copper sulphate 

 and amalgamated zinc in dilute sulphuric acid 

 (1 volume of commercial sulphuric acid to 10 

 volumes of distilled water) 



D aniell : — 



Copper in saturated solution of copper sulphate 

 and amalgamated zinc in dilute sulphuric acid 

 (1 volume of commercial sulphuric acid to 8 

 volumes of distilled water) 



Carbon and zinc in a saturated aqueous solution 

 of potassium bichromate 



0-532 



0-713 



0-760 

 0-821 

 0-838 



0-856 



0-923 



0-958 



0-982 

 0-996 



