TEE VISCOMETEE

The left limb of the viscometer was evacuated by means of
the mercury head Q in order to draw the liquid through the
capillary.

Having run in a little more than the required amount of
liquid, the viscometer and frame were placed in the bath B of
Fig. 25 and the limbs of the viscometer were connected to the
pressure outlets on either side.
With the temperature main-
tained constant at the lowest
point at which measurements
were desired, the cock Zr (or 2)
was turned to air and the cock Z
(or Z') to pressure. As the liquid
rose in the left limb, it finally
overran in to the trap T/ Fig. 22.
At the instant that the meniscus
in the right limb reached the
point k2j the cock Z was turned
to air. Thus the working volume
was adjusted.

A measurement of the fluidity
is made by turning the cock Zf
to pressure and immediately read-
ing the pressure on the manom-
eter as well as the temperature of
the manometer, while the liquid
is flowing out of the bulb V. As
the meniscus passes the point
ra' the time recorded is begun.
Keeping the temperature constant
the time is taken as the meniscus

passes the point W2. The preS- FIG. 27.—Pilling device of Thorpe
. ,, , i <• j and Rodger.

sure is then read as before, and

before the meniscus reaches the point &' the left limb is again
turned to air. The apparatus is then ready for a duplicate
observation in the opposite direction.

The Calculation.—The corrections to the time and temperature
are not peculiar to viscosity measurements and need no special
comment. In obtaining the pressure, several corrections must