CONDUCTIVITY ANM> U'MIXOSITY OF FI.AMKs O>\TAIM\r. V.\pl;lSKI> SALTS. 127 



known from independent evidence, that great caution is necessary before declnrin^ that 

 the results i>f such experiments as we have undertaken establish any one possible view. 



The most important generalisations derivable from our study of the relation between 

 current strength and concentration of different sets of salts of different metals are 

 first, that the conductivities differ always according to the metal ; secondly, that 

 among salts of the same metal differences of conductivities evident at high concen- 

 trations disappear when the dilution is greater ; and thirdly, that the conductivity of 

 haloid salts is different from the conductivity of oxysalts. 



We will give the explanation of these general facts, which appears to be most in 

 conformity with our results, and most compatible with chemical evidence. 



The fact that the conductivity of haloid salts at higher concentrations is approxi- 

 mately proportional to the square root of the concentration is consistent with the 

 presence of a binary electrolyte, and as we have found that the conductivity of 

 chlorides is maintained when the presence of a large quantity of chloroform in the 

 flame forbids us to suppose that the chlorides are chemically altered, we conclude that 

 the binary electrolyte in question is the haloid salt itself. 



Again, the approximately equal conductivity of the oxysalts of any one metal which 

 approaches that of the hydrates, indicates that in the flame they are changed into the 

 same electrolysable substance, which we conclude is the hydroxide or oxide. 



At the same time, whilst we recognise the haloid salts as being present to a con- 

 siderable extent undecomposed in the flame, and acting as electrolytes, the fact that 

 at high dilution the haloid salts and oxysalts alike of any one metal have the same 

 conducting power, makes it probable that under these circumstances the haloid salts 

 have also been converted into hydroxides, thus giving a common dissociating body. 



The fact that potassium iodide at higher concentrations has a greater conductivity 

 than potassium chloride, or bromide, is compatible with the greater readiness with 

 which this salt is acted upon by oxidising agents. Whilst the chloride and bromide 

 preserve their individuality, the iodide is largely converted into the oxide, which has 

 a higher conductivity. 



Coming lastly to the question whether the luminosity in flames coloured by salt 

 vapours is connected with their electrical conductivity, we think our observations on 

 flames containing chloroform give a definite decision in the negative. 



The addition of chloroform to a flame produces hydrochloric acid. Now the 

 conductivity of a flame containing either chloroform or hydrochloric acid, but no 

 salt, is shown by our experiments (see p. 121) to be extremely small. Since in a 

 flame containing an alkaline chloride the conductivity depends on the ionisation of 

 this salt, the increased concentration of the chlorine ions due to the introduction of 

 chloroform is so small that the degree of ionisation is not materially reduced and the 

 conductivity therefore is not greatly affected. 



The coloration of the flame is, however, entirely destroyed by the addition of 

 chloroform. 



