132

FLUIDITY AND PLASTICITY

This formula reproduces observed values of all classes of com-
pounds with remarkable fidelity, but it contains four constants.
Finally Batschinski (1901) has indicated that the viscosity
varies inversely as the cube of the absolute temperature

E
n = |3 (52)

where E is dependent upon the nature of the liquid and is called
"the viscosity parameter." Using the data of Thorpe and
Rodger, Pribram and Handl, Gartenmeister and others, Bats-
chinski has tested his expression fully. While it gives very good

z

Temperature absolute
FIG. 48.—Diagram illustrating ideal fluidity-temperature curves.
agreement in many cases, there are numerous exceptions, particu-
larly water, the alcohols, acids and anhydrides (cf. Eq. (41)
for mercury).
Fluidity and Temperature.—From the evidence given in Chap-
ter I to prove that fluidities are normally additive in homogeneous
mixtures, it would appear probable that fluidity-temperature
curves in their simplest form are straight lines, and since every
Kquid is theoretically capable of existing in an undercooled
condition, these curves meet at absolute zero. The equation for
the fluidity-temperature curves of all substances should be
<p= aT
which is the same as Eq. (43). A family of curves would present
the appearance shown diagrammatically in Fig. 48.