246 ELECTROLYSIS. 



treating 1,000,000 kilogrammes of zinc would be 1,000,000 

 francs, whereas it would not exceed 500,000 francs if acting by 

 electrolysis and adopting his system. He has also calculated 

 that with a judicious use of electricity he could attain a daily 

 production of 10 to 12 kilogrammes of zinc per horse-power. 



These calculations are somewhat premature and are of no 

 industrial value, for they are based on doubtful hypotheses 

 instead of precise and repeated trials. 



The only verified experiment of M. Letrange's process was 

 realised in 1882, by M. Cadiat, under the direction of our lamented 

 friend Alfred Niaudet. It gave the following results : 



Number of baths in tension ...... 5 



Intensity of the current in amperes . . 75 



Electromotive force in volts ...... 13 '05 



Duration of the experiment ...... 4h. 15m. 



Weight of zinc obtained ........ l'475kil. 



The No. 2 Gramme machine used in this experiment had a 

 mechanical efficiency of 75. 



The expenditure of work was, therefore, 



75 x 13-05 



Thus, to obtain 1 475 kilogramme of zinc, 133 kilogram- 

 metres had to be consumed during 4 hours and 15 minutes, 

 which corresponds to 565 kilogrammetres in 1 hour, and to 

 5 horse-power for 1 kilogramme per hour. 



In order to ascertain the industrial efficiency of this experi- 

 ment, it is necessary to determine the amount of motive power 

 required for the dissociation of the zinc from its sulphate. 



The heat of formation of 1 equivalent of sulphate of zinc is 

 53 '5 calories. 



One equivalent of sulphate of zinc contains 32 7 grammes 



of zinc. Therefore - ^ - calories will be required for 



oZ 



the liberation of 1 kilogramme of zinc; this corresponds to 

 693,664 kilogrammetres, and to 2 '6 horse-power during one 

 hour. 



Theoretically, 2 ' 6 horse-power must liberate 1 kilogramme 



