176

FLUIDITY AND PLASTICITY

where the concentrations are molecular and not volume concen-
trations.

In the above equimolecular mixture, if we let y represent the

number of milliliters of ether which are combined in every 100

ml of mixture, the volume of the chloroform combined will be

0.7366 X 119.36y _

74.08X1.526

where the specific gravities of ether pe and chloroform pc are
taken as 0.7366 and 1.526 respectively and their molecular
weights, me and mc) 74.08 and 119.36. Since the sum of the two
volumes y + 0.7777?/ is 9.71, the volume of the ether combined
is 5.46 ml and the volume of the chloroform is 4.25 ml.

Substituting the molecular concentrations in the above formula

K = [(56.26 - 5.46Wme][(43.74 - 4.25)Pc/mc] ^

9.71p/(me+mc)

where p is the density of the compound calculated by averages
to be 1.082.

With this value of K, it is possible to calculate the absolute
temperature corresponding to a fluidity of 200 for any mixture
on the assumption that only one compound is formed and that
the Law of Mass Action is obeyed. Thus for any mixture if a
is the volume percentage of ether and z is the fraction of the
ether which is combined,

mc

= 4.696

me

For the 28.21 volume per cent ether mixture, z = 0.157. The
volume of ether in 100 ml which is combined is az = 4.43 ml,
and the volume of chloroform combined is 0.7777 X 4.43 =
3.44 ml. Hence the calculated absolute temperature correspond-
ing to a fluidity of 200 is
0.2378 X 216.5 + 0.6835 X 305.3 + 0.0787 X 538.6 = 302.5°
which is in fair agreement with the value read from the curve
of 297.4°.
ETHYL ALCOHOL AND WATEE MIXTURES
We will now take up a case in which the components of the
mixture are highly associated. Ethyl alcohol and water are a