FLUIDITY AND TEMPERATURE

137

observed values is 0.17 for the 87 substances and based on some
1,OOO duplicate observations. If we omit the alcohols, this
difference falls to 0.09 for 70 substances. This is much better
than Thorpe and Rodger obtained with Slotte's
, since the percentage difference is nearly twice the
, viz., 0.15 per cent for 64 substances. But the real test
is with substances which give fluidity curves departing widely
from the linear type and here Slotte's equation breaks down
completely.

For this type of substances, the fluidity Eq. (53) with three
constants does not reproduce the observed values to the limit of
experimental error, but a great improvement can be made by
introducing another constant and writing the equation

T-Av + C- (54)

For example, the mean divergence between the observed and
calculated values for the eight substances, which gave the largest
percentage difference, was 0.77 per cent with the simpler for-
mula; the Eq. (54) with four constants reduces this to only
O.O7 per cent which is nearly within the limits of the experi-
ixiental error. In the case of water, which gave a mean difference
of only 0.17 per cent with the simpler formula, the difference is
reduced to 0.01 per cent and similarly in the case of octane it is
reduced from 0.16 to 0.02 per cent. For reference, the constants
for these substances are given in Table XXXV.

XXXV.—THE CONSTANTS IN THE EQUATION T = A<p -f- C —

Mean

Substance
A
B
C
D
per cent

difference

"Water
0 23275
8,676 8
309 17
120
0 01

Octane. ...
0 14507
100,745.0
438 . 10
400
0.02

TEfcijrbyric acid ................
0.16154
70,630.0
504.44
250
0.02

Isofc>utyric acid ..............
0.23862
43,665.0
433 . 17
200
0.06

JPropionic acid anhydride .....
0.23619
52,294.0
425 . 82
250
0.07

IBTityl alcohol ...... ..........
0.23605
4,802.0
349.71
40
0.04

Isotoutyl alcohol .............
0.23700
2,993.7
340.66
30
0.09

-A.csti.ve amyl alcohol
0.24650
2,942.8
346 . 82
30
0.08

Inactive amyl alcohol ........
0.24101
3,908.7
354.17
35
0.09

H>i methyl ethyl carbinol ......
0.22988
2,124.0
328.84
30
0.09