CHAPTER III

AND TEMPERATURE, VOLUME AND PRES-
SURE ; COLLISIONAL AND DIFFUSIONAL VISCOSITY

have established in the preceding chapter that the vis-
cosity of a substance is closely dependent upon the magnitude
of the molecules making up the substance. In this and succeed-
chapters we will investigate the relation between viscosity
various physical properties.
Temperature. — Prior to 1800, water was considered to be
perfectly fluid, but by causing equal volumes of water at corre-
sponding pressures to flow through tubes of given dimensions
Gorstner in that year proved that the fluidity (Flussigkeit)
of water varies considerably with the temperature.

"We have already seen that Poiseuille expressed this change in
the form of the parabolic equation

K = a + bTc + cTc*. (36)

A.f ter viscosity had been defined, 0. E. Meyer (1861) introduced
ttte viscosity coefficient into the formula which then became

77 =

(37)

where rj0 is the viscosity at 0°C and Tc is the temperature
Oontigra/de. In spite of the fact that the two equations are not
interchangeable, the latter formula is usually associated with the
n.o,rne of Poiseuille. We will refer to it as the Meyer-Poiseuille
formula. It holds for water from 0 to 45° with a maximum
deviation of 1 per cent. For temperatures above 45° Meyer and
Rosencranz (1877) proposed the formula

"Various investigators have employed the Meyer-Poiseuille
formula and confirmed the fact of its limited applicability. We
may mention Grotrian (1877), Noack (1886), Thorpe and
Rodger (1893), Knibbs (1895).
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