274 FLUIDITY AND PLASTICITY
unless they serve to remove the contaminating film of grease
which is already present.
These results lead one to the observation that in difficult cases
of lubrication, where seizure is always possible and is almost
certain to be very disastrous, the use of pure mineral oil may not
be the best practice. On the other hand, there is not enough of
the fixed oils to supply the imperative demands of mankind for
edible fats, soaps, leather dressing, et cet. Fortunately however
it is likely that all of the benefit of the use of lard oil as a lubricant
can be obtained very cheaply by adding to mineral oils small
amounts of certain substances possessing high adhesion, par-
ticularly substances with unsaturated groups in their molecules,
such as are found in oleic acid, turpentine, pine oil et cet. Some
of these substances are already being used on a somewhat
extensive scale in successful substitutes for cutting oils. The
use of these substitutes opens up a field for research which
is most fascinating and in view of the approaching exhaustion
of our supplies of petroleum, the study is so practical that it
cannot long be postponed. Of its importance we can do no
better than quote from an editorial in the Chemical Trade
Journal for December 1920: " Before the war the annual expendi-
ture on lubricants in England was £6,000,000 and it is estimated
that an annual saving of one to two millions could be effected
if a systematic investigation were undertaken and the results
made freely available to the public. Furthermore the loss
caused by improper lubrication, would represent a very large
addition to the figure given above."
Asphalt-base Versus Paraffin-base Oils.—With lubricants in
use made from crude oils from different fields, the question has
arisen whether the paraffin-base or the asphalt-base oil is supe-
rior, but there is a notable lack of convincing evidence in favor
of either. We offer the following evidence to prove that the
differences between them may be very considerable, and that
the chemical composition as determined by the source of the
oil is not a matter of indifference to the consumer; this is par-
ticularly true in aeroplane lubrication where the results of faulty
lubrication are so very disastrous.1
i i; l The walls of the aeroplane motor, the crankshaft et cet. are made so
,1( light that the seizure of a siagle bearing will result in the wrecking of the