194

FLUIDITY AND PLASTICITY

Foussereau (1885) has examined the changes in fluidity and
conductivity of pure water with the temperature and proved
that the conductivity is directly proportional to the fluidity.
He has also examined several fused salts and salt mixtures and
obtained a similar result. We reproduce in Table LI his results
for sodium nitrate, potassium nitrate and an equimolecular mix-
ture of the two salts. It is to be observed that not only is the ratio
different for the different salts but the conductivity is relatively
much higher for the mixture than for either of the individual salts.

Vollmer (1894) studied solutions of various salts in methyl
and ethyl alcohols and found the temperature coefficients of

TABLE LII.—THE FLUIDITY AND CONDUCTIVITY OF TETRAETHYLAMMONIUM

IODIDE AT INFINITE DILUTION IN VAEIOUS SOLVENTS AT 0° AND 25°C

(AFTER WALDEN)

Solvent
*°°
AO°
ACO
<P/Aco
^
A 25°
Aoo
¥?/Aoo

Acetone
252 0
177 0
1 41
316 0
225 0
1 41

Propionitrile ....
185.0
129.0
1 43
242 0
165 0
1 47

Methyl alcohol .......
118.0
90.0
1.31
172.0
124 0
1.39

Ethyl mustard oil ........
118.0
82.0
1.44
162.0
106.0
1.53

Acetylacetone
87 0
57 0
1 52
128 0
82 0
1 56

Ethyl alcohol
55 9
37 0
1 51
92 6
60 0
1 54

Benzonitrile ...
51.6
35.5
1 45
80 0
56 5
1 42

Nitrobenzene ...........
32.6
25.0
1 30
55 0
40 0
1 37

fluidity and conductivity very nearly identical. Walden (1906)
has gone further and proved that ^>/A«, is a constant even when the
solvent is varied widely. He used tetraethylammonium iodide
in some forty different organic solvents and found <p/Aa = 1.43,
which is independent both of the nature of the solvent and of the
temperature. A portion of his data will serve to show the nature
of the concordance.
These researches all point to the conclusion that Stokes' Law,
with a possible correction as already suggested, holds for the dif-
fusion of molecules and ions, so that if a given particle has the
same size in different solvents and at different temperatures,
the velocity imparted by a constant force will be proportional
to the fluidity of the medium.