116

methylene group to heptane is less and the effect of adding
other methylene groups must be still less, otherwise it would
require no very high molecular weight to give a negative fluidity,
which is inconceivable.

The fluidity of 200 is chosen as a basis of comparison in order
that as large a number of substances as possible may be included.
The absolute temperatures and slopes of several unassociated

FLUIDITY AND PLASTICITY

FIG. 46.—The fluidities of various alcohols at different temperatures. 62.
Methyl alcohol; 63. Ethyl alcohol; 64. Propyl alcohol; 65. Isopropyl alcohol;
66. Butyl alcohol; 67. Isobutyl alcohol; 68. Trimethyl carbinol; 69. Active
amyl alcohol; 70. Inactive amyl alcohol; 71. Dimethylethylcarbinol; 72.
Allyl alcohol.
compounds corresponding to the fluidity of 200 are given in
Table XXV. The third column of this table shows that the
value of a methylene grouping varies around a mean value of
22.7, the mean deviation from this value being 3. The effect
of an iso-grouping is to decrease the temperature required by
about 7.6°, as shown in Table XXVL