166 ELECTROLYSIS. 



The basis of his system consists in giving to the cylinder 

 which is being coated a rapid rotary motion in the copper bath, 

 so as to constantly bring the metallic surface in contact with 

 new layers of the electrolyte ; this allows of the use of powerful 

 electric currents for small surfaces of cathodes without inter- 

 fering with the quality of the deposited copper. 



SCHLTJMBERGER'S PROCESS.* The cylinder (having been 

 perfectly cleaned by the usual methods) is made the cathode 

 for the space of 24 hours, in a mixture of two liquids, com- 

 posed of 



Parts. 



Water 16 



Sodic carbonate . . . . 4 



sulphate 2 



Cnpric sulphate .. .. 1 



It is then washed, rubbed with pumice powder, then washed 

 again with an aqueous solution of cupric sulphate containing 

 ^^ part of its volume of sulphuric acid, scraps of copper being 

 kept in the bath to prevent the liquid becoming too acid. It 

 is immersed again in the above alkaline solution, or else in a 

 mixture composed of two liquids, viz : 



Water 12 



Cyanide of potassium .. 3 



Parts. 



Water 10 



Cyanide of potassium . . 3 

 Aqueous ammonia . . . . 3 



Parts. 



Water 10 



Sodic carbonate . . . . 4 

 sulphate 2 



Cupric acetate 2 



In these mixtures, at a temperature of 15 to 18 C., it is 

 surrounded by porous cells containing zinc rods and dilute 

 sulphuric acid, and connected with the zinc by copper wires. 

 The cylinders are turned partly round once a day, in order to 

 render the deposit uniform, and the action is continued during 

 three or four weeks, until the deposit is -f^th of an inch. 



COPPERING OF TELEGRAPHIC WIRES. The industry of 

 coating with copper steel wire used for telegraph lines is carried 

 out on a large scale in the works of the Postal Telegraph 

 Company at New York. 



These works have 200 baths of sulphate of copper and 25 

 large dynamo-electric machines. 



* ' Electro-metallurgy,' Gore. 



