THE ELECTRIC CURRENT. 1 1 



of these monovalent metals are directly proportional to their 

 atomic weights. 



The charge on an ion is proportional to its valency. Thus, the 

 copper ion in a solution of cupric chloride (CuCl 2 ) has twice as 

 much charge as the copper ion in a solution of cuprous chloride 

 (Cud), so that half as many cupric ions as cuprous ions are de- 

 posited by a given current in a given time. In general, if n is 

 the number of monovalent ions deposited in one second by one 

 ampere, then nJ2 is the number of bivalent ions deposited in 

 the same time by the same current, / 3 is the number of trivalent 

 ions deposited in the same time by the same current, and so on. 



Consider a series of chlorides of metals of different valencies, 

 for example, sodium chloride (NaCl), cupric chloride (CuCl 2 ), 

 ferric chloride (FeCl 3 ), and stannic chloride (SnCl 4 ). Reduc- 

 ing these all to a given amount, say n atoms, of chlorine, we 

 would have n atoms of sodium (Na), n/2 atoms of copper 

 (Cu), w/3 atoms of iron (Fe), and w/4 atoms of tin (Sn); so 

 that, during the liberation of n atoms of chlorine, we would 

 have a deposit of n atoms of sodium (Na), nJ2 atoms of 

 copper (Cu), nj $ atoms of iron (Fe), and 72/4 atoms of tin 

 (Sn). Therefore, the weights of these various metallic deposits 

 would be proportional to their atomic weights divided by their 

 respective valencies. 



Let us represent each unit of charge by a plus or minus sign. 

 Then the single, double, triple and quadruple charges on the ions 

 of sodium, copper, iron and tin may be represented as follows : 

 Na , Cut, Fe| and Sn|, and the single and double charges upon 

 the monovalent and bivalent anions of chlorine and SO 4 may be 

 represented as follows : Cl and ~ SO 4 . The present hypothe- 

 sis concerning chemical affinity is that it is due to the attraction 

 ol the opposite charges on the two constituents of the molecule. 

 Thus, sodium and chlorine are held together in the molecule of 

 sodium chloride by the attraction of the positive charge on the 

 sodium for the negative charge on the chlorine, as may be repre- 

 sented thus : Na -\ Cl. 



