208 



Dr. H. A. Wilson on the Laws of 



Under these circumstances it does not seem to be justifiable 

 to make the simple supposition mentioned above, at least not 

 without further experimental evidence in its favour. 



The experiments now to be described show conclusively 

 that above 1300° C. there is a very close analogy between 

 salt- vapours and liquid electrolytes. In fact it is shown that 

 Faraday's laws of electrolysis are strictly applicable to salt- 

 vapours just as to salt- solutions. 



It is probable that the gaseous ions attract neutral mole- 

 cules to themselves, which accounts for their small velocities ; 

 and apparently the positive ions condense many more mole- 

 cules in this way than the negative ions, so that the negative 

 ions move much the faster. But this condensation, which 

 appears to be peculiar to ions in the gaseous state, need not 

 affect the number of ions produced by the dissociation of one 

 salt molecule or the charges which they carry. It will be 

 shown below that a salt in the state of vapour gives rise to 

 the same number of ions carrying the same charges as a 

 salt in an aqueous solution, in other words, the capacity of a 

 salt-vapour for transporting electricity is the same as the 

 capacity of an equal amount of salt in the state of solution. 



The apparatus used is shown in the accompanying figure. 



It consisted of a platinum tube TT ; 40 centims. long and 

 0*75 centim. ft diameter, having a flange FF 6 centims. in 

 diameter joined on at one end. This tube was supported 

 horizontally in a Fletcher's tube furnace. The flange served 

 to keep the furnace gases from the open end of the tube. 

 An electrode EE, consisting of a platinum tube 12 centims. 

 long and 0*3 centim. in diameter, was supported, on an ad- 

 justable insulating stand, along the axis of the tube TT f . 



