THE FLUIDITY OF SOLUTIONS

171

components. He assumed that the free volume per unit of
limiting volume was the same for each kind of molecule, so that
from the equations

and

v = mo i

the values of Vi and v% could be calculated. He then calculated
the fluidities of the mixture by means of the simple additive
fluidity formula (25). That the values calculated by Gibson
agree well with the observed is shown in the third line of fluidities
for each temperature given in Table XLIV,

TABLE XLV.—THE SPECIFIC VOLUMES IN MILLILITERS PER GRAM OF

MIXTURES OF METHYL IODIDE AND CARBON DISULPPIDE (FROM

THORPE AND RODGER)

Temperature
Per cent carbon disulphide by volume

0
33.22
53.39
62.61
79.94
89.42
100

0
0.4285
0.5040 0.5031
0.5643 0.5624
0.5959 0.5945
0.6675 0.6659
0.7146 0.7128
0.7740
Observed Calculated

10
0.4336
0.5100
0.5712
0.6031
0.6754
0.7229
0.7830
Observed

20
0.4390
0.5163 0.5152
0.5781 0.5759
0.6104 0.6087
0.6835 0.6817
0.7315 0.7297
0.7923
Observed Calculated

30
0.4445
0.5228
0.5853
0.6179
0.6918
0.7412
0.8018
Observed

40
0.4502
0.5295 0.5282
0.5927 0.5904
0.6257 0.6242
0.7004 0.6987
0.7495 0.7475
0.8118
Observed Calculated

We have come now to the case where there is chemical com-
bination on mixing. There is generally a decrease in volume
and the specific volume-weight concentration curve, curve II,
Fig. 60, is sagged as well as curve V, Fig. 61, representing the
specific volume-volume concentration curve. Since new sub-
stances are formed, no method given thus far can be depended
upon for calculating the fluidity-volume concentration curve.