ELECTEICAL COE'DUCTIVITY OF AIR AEL) SALT VAPOURS. 
435 
low tempei-atiires'^' where the current is small coinparecl with that recpiired to 
completely electrolyse the salt. At 250° C. a current of 2 X 10 "'' ampere was 
obtained with 40 volts, and at 300° a current of 4 X 10“’^. Hence the energy 
required to ionize 1 gramme molecule of KI is about 15,000 calories, or about one 
quarter that necessary to ionize a gramme molecule of air. 
Diagram No. 15 shows the variation of the current with the temperature for 
K 0 CO 3 , a solution containing 10 grammes in a litre, being sprayed with an E.M.F. of 
400 volts. 
Diagram No. 16 shows the variation of the current with the temperature for KCl 
with an E.M.F. of 800 volts. 
* At high temperatui'es the per cent, of the salt ionized is not small, so that the method used for 
calcidating the energy breaks down. 
3 K 2 
