196

FLUIDITY AND PLASTICITY

iodide solutions, and he finds that in no case does the value of m
depart from unity by more than 0.2.

Johnston has calculated the value of m for many cations
and anions using different temperatures from 0 to 156°, but
found that no single value could be assigned for the hydrogen
and hydroxyl ions. The following table will show the nature
of his results.

TABLE LIIL—THE RELATION BETWEEN THE CONDUCTANCES AND THE
FLUIDITIES OF THE INDIVIDUAL IONS AT DIFFERENT TEMPEEATUEES C

(AFTER JOHNSTON)

Ion
A°;
m
^/Aco
0°
^/Aco
100°
^J/Aco
156°

K.
40.4
0.887
1 39
1 71
1 81

NH4 ...... '. . .
40.2
0.891
1 40
1 71
1 80

Cl ............
41.1
0.88
1.37
1 70
1 81

NO3
40.4
0.807
1 39
1 98
2 19

Na ...........
26.0
0.97
2 16
2 27
2 31

HCa
30 0
1 008
1 88
1 84
1 84

C2H302. .
20.3
1 008
2 77
2 73
2 73

J^SOi .........
41.0
0.944
1 36
1 51
1 55

H
240 0

0 234
0 550
0 741

OH..
105 0

0 535
0 806
0 971

The slightly hydrated ions K, NH4, Cl, and N03 have*a
high conductivity and a small value of m, corresponding toj|n
increasing ratio of ^/A^; the presumably highly hydrated ions
Na, HCa, C2H302, and 1/2S04 have a low conductivity, a high
value of m and a nearly constant ratio of p/A^. Hydrogen
and hydroxyl are most like the unhydrated group of ions in that
they have a very high conductance and a low but rapidly
increasing value of &/&&.
The explanation of these curious facts is not at hand, but
apparently we must assume that the conductivity does vary
directly in proportion to the fluidity and seek to explain the
inconstancy of the v/A.^ ratio in the changing solvation of the
ions. The phenomenon is as if the unhydrated ions increased in
volume with the temperature, whereas the hydrated ions do not.