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XXI. Atomic Conductivities of the Ions. 

 By Philip Blackman *. 



fTVHE fact that there exists a definite quantitative relation 

 JL between molecular conductivities (Phil. Mag. 1906, xi. 

 p. 416 ; Ostwald's Lehrbuch der Alg. Chemie, II. i. p. 672) 

 seems to indicate unmistakably that molecular conductivities 

 are additive properties, i. e., that the molecular conductivity 

 o£ any substance (in aqueous solution) is equal to the sum of 

 the atomic conductivities of its constituent ions. No such 

 regularity apparently exists between the molecular con- 

 ductivities of the acids, but if the assumption be made that, 

 the atomic conductivity of the H" ion is a function of the 

 relative strengths of acids, then it is possible to calculate its 

 value, and consequently those of other ions. 



It was shown (Phil. Mag. 1906, xi. p. 417) that in the 

 general equation 



fiv ax + fiv Mi011 - /xv UiX = K, 



the disappearance of molecular conductivity was equivalent 

 to that required by the equation H" + OH/ = H.OH for the 

 particular acid in question. Then, according to the preceding 

 argument, the atomic conductivity (fiv K ) of the H* ion may 

 be determined from the equations 



(in which Rv HX , P^ HX , R^ HX » e ^ c -' represent, respectively, the 

 relative strengths of the acids HX, HXj, HX 2 , etc., all 

 measured at the same concentration, v, and at the same 

 temperature). 



The calculations effected by means of these equations are 

 so fairly consistent that the assumptions made above may 

 very reasonably be taken as correct. 



As an example, the atomic conductivities of the ions H*, 

 OH', K*, and CI', at 18° and at concentration v = 500, are 

 worked out in full. 



-"hci> -^hno 3 ' -"$ij 2 so 4 > -^- 2 l h 2 c 2 o 4 ' anc * -^cii 3 co 2 ii 



* Communicated by the Author. 



