Page:Outlines of Physical Chemistry - 1899.djvu/219

 CONDUCTIVITY OF ELECTROLYTES

��3. The molecular conductivity increases with the dilution up to a maximum which, in the case of good con- ductors, can be practically attained and corresponds to a solution of one equivalent in about 2,000 litres of water.

The following table gives some molecular conductivities at 18° from observations by Kohlrausch :

��Dilution

�KOI

�NaOl

�LiOl

�iBaCl a (

�iK 9 S0«

�1 litre

�10 litres

�100 „

�1,000 „

�10,000 „

�50,000 „

�100,000 „

��The increase in the conductivity with dilution varies according to the nature of the salt. The variation is small for salts formed of two monovalent ions, greater for salts of the type BaCl 2, and still greater for those of the type MgS0 4.

4. The maximum molecular conductivity (/i <» ) of an organic acid may be deduced from an experimental study of its sodium salt. But the value for /* ^ may also be obtained from the following data valid at 25° :

��an acid containing

�12 atoms

�>» »>

�»»

�»» »

�>»

�>» »»

�>>

�t» »»

�»>

�»> »»

�»>

��For acetic acid /i ^ = 864, for propionic acid 859, and for benzoic acid 856.

��modification of the equilibrium, or, what is the same, a decrease of the dissociation. Consequently, there will be a diminution in the conductivity which more than compensates for the increased mobility of the ions.

�� �