IONIC VELOCITIES. 



379 



of " electrical friction," Kohlrausch gives a table of coeffi- 

 cients at a temperature of i8° C, from which the following 

 numbers are taken : — 



From a list of ionic velocities, such as that given on the 

 opposite page, the conductivity of any salt solution can be 

 calculated by taking the sum of the opposite velocities of 

 its ions, and the result compared with observation. 



This comparison would be difficult at very great dilution, 

 so Kohlrausch took solutions of one-tenth of a gram-equiv- 

 alent per litre, when in general the velocities are approaching 

 their limiting value. He gives a table of twenty-five elec- 

 trolytes, the numbers for which all agree well with observa- 

 tion (Wied. Ann., xxvi., p. 215). The following are fair 

 examples — the numbers being reduced to C.G.S. units : — 





In the case of substances whose molecular conductivity 

 varies greatly between a strength of one-tenth gram-equiv- 

 alent per litre, and infinite dilution, the effect of concentra- 

 tion is so great that no agreement is obtained ; thus acetic 



1 The latest numbers are rather greater than these, but the differences 

 affect both observed and calculated results equally, so the comparison is 

 the same. 



