CHEMICAL EFFECTS OF ELECTEIC CUKKENTS 219 



gold-plating, and platinum-plating may be done. Many of 

 the articles we use in everyday life have been plated with 

 gold, silver, brass, or nickel. 



227. The rate of deposit. If a solution of nickel sulphate 

 or zinc sulphate is used in the plating tank, with a nickel 

 anode or a zinc anode in the respective cases, different weights 

 of metal will be deposited when the current flows the same 

 length of time. Michael Faraday first determined these facts 

 with exactness in the year 1834. 



The weights of various elements set free in a given time 

 are shown in the table below: 



To obtain the weight of metal deposited by a certain cur- 

 rent in a given time, we need only multiply the strength of 

 the current in amperes by the amount of metal deposited 

 by one ampere in an hour and multiply this product by the 

 tune in hours. 



So regular is the amount of material deposited under the 

 same conditions that an ampere is often defined as the steady 

 current which will deposit 4.025 grams of silver in one hour 

 from a standard silver-plating solution. As already learned 

 (sect. 218), it can be defined as the current forced through 

 a resistance of one ohm by an electrical pressure of one volt. 



