308

FLUIDITY AND PLASTICITY

To assist in the regulation, cold water is admitted, when desired,

by a cock at S. A drain pipe, Q, maintains the bath at a constant

level. It may also be unscrewed to permit draining the water

from the bath. The bath is insulated on two sides.

THE DENSITY

It is not necessary to know the exact density in
order to obtain the fluidity by this method. But
the density can be measured at the same time
with accuracy with little additional labor. Since
the fluidity is very closely related to the volume,
according to the law that the fluidity is directly
proportional to the free volume, the specific volume
should usually be obtained with precision.

The instrument shown in Fig. 94 is convenient to
use and unlike the Sprengel pycnometer, it can be
used to determine the density below room tem-
perature. It is filled to the mark with water and
weighed at every temperature at which it is to
be used. It is then cleaned, dried, weighed, and
filled with the liquid to be determined and again
weighed. The ratio of the weights of liquid cor-
rected simply for the buoyancy of the air gives the
correct specific gravity referred to water at 4°C.
The densities of water are given in Table VI.
TABLE VI.—DENSITY AND VOLUME OF WATER IN GRAMS PER MILLILITER

\

FIG. 94.—-
A pycnometer
for liquids.

Temperature
Density
Logarithm density
Specific volume

0
0.99987
9.99994-10
1.00013

10
0.99973
9.99988-10
1.00027

20
0.99823
9.99923-10
1.00177

30
0.99568
9.99811-10
1 . 00435

40
0.99225
9.99662-10
1.00782

50
0.98807
9.99479-10
1.01207

60
0.98324
9.99266-10
1.01705

70
0.97781
9.99025-10
1.02270

80
0.97183
9.98759-10
1.02899

90
0.96534
9.98468-10
1.03590

100
0.95838
9.98154-10
1.04343