190 ELECTROLYSIS. 



2nd. Prepare separately : 



A solution of 12 kilogrammes of potassic tartrate in 320 

 litres of water. 



A solution of 31 kilogrammes of caustic potash in 230 litres 

 of water. 



A solution of 20 kilogrammes of stannic chloride (100 

 grammes of tin per 5 litres). 



These three solutions are mixed as pre\ 7 iously indicated, 

 stirring continuously. 



The electric current must have a tension of 3 to 4 volts. 



The iron and cast iron articles are covered with a copper 

 coating before being tinned. 



LOBSTEIN'S PROCESS. We find in Mr. Napier's treatise the 

 following information relating to M. Lobstein's process which 

 has been more particularly used in England. The battery is 

 formed with a leaden vessel 1*20 metre long by '60 metre 

 wide and 2 -25 metres deep. At the bottom are placed a copper 

 sheet of 1*35 metre by 0*70 metre, on the top of which is a 

 zinc sheet of 1 * 05 metre by 67 metre. The exciting solution 

 contains 4 kilogrammes of plumbic acetate, 4 kilogrammes of 

 common salt, and 1 kilogramme of sulphuric acid in as much 

 water as may be required for filling the vessel until the copper 

 and zinc are covered. 



The tinning bath is 2 '40 metres long by 1'20 metre wide, 

 and 1 ' 20 metre deep. It contains 2270 litres of water in 

 which has been dissolved 40 kilogrammes of caustic soda, 1 kilo- 

 gramme of potassic cyanide, and 700 grammes of tin salts*. 

 The tin electrodes are connected to the copper of the battery ; 

 the iron sheets upon which the deposit is effected measure 

 15 square metres. 



The result of an operation lasting 96 hours was: 



Zinc dissolved in the cell 748 grammes. 



Tin dissolved in the electrodes .. ..888 

 Tin deposited on the iron 361 



As may be seen, this method is neither rapid nor economical ; 

 we describe it as it received a few years ago a great publicity. 

 MAISTRASSE'S PROCESS.* M. Maistrasse uses a tinning bath 



* Julius Weiss, 1883. 



