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32
Accordingly, when in 1942 the Japanese advance robbed us of
our main sources of former natural insecticides, pyrethrum and derris,
D.D.T. was brought into large-scale production in America and in
England. Thereafter it joined with our new quinine-substitute,
mepacrine, in becoming a major weapon of war in Burma. Together
these two enabled our troops to fight through that terrible country and
to fight on even during the monsoon. What mepacrine did to protect
the soldier from the mosquito, D.D.T. did to bring down the insects
in flight and to kill their larvae in the swamps.
In 1943 D.D.T. performed a second miracle, in Naples. Faced
with a sharp outbreak of typhus, the military authorities promptly
brought this wonder-chemical to bear upon the body-lice of the local
population, as many as 72,000 of them being treated in one day. In
this way, for the first time in history, a winter epidemic of typhus was
stamped out at its source. A similar epidemic at the close of the 191418
war had spread throughout the Balkan countries costing over
3,000,000 lives in Russia alone.
When in 1944 the news of these dramatic successes was first
released, sensational claims for D.D.T. were made in press-reports,
some even foreshadowing a world freed at last from all insect-pests.
As a precaution, now that D.D.T. is made available for civil purposes,
the public will do well to discount some of the romance and avoid
exploitation by buying D.D.T. only from responsible firms, who
standardise their products, and at the same time by learning something
of its limitations.
Crude D.D.T. is a white powder which is insoluble in water but
soluble in certain oily liquids. It is never applied in neat strength,
but after dilution in the form of a liquid, a powder or a gas.
As a liquid, D.D.T. may be made up into an emulsion with water,
but it is more widely useful when dissolved in kerosene or paraffin.
Since the solvent may affect household paint, D.D.T. has recently been
compounded with an oil-bound water paint or whitewash in which
state it is actually claimed to retain its activity for a longer period
than when sprayed upon a painted surface. These experiments are
still continuing.
When sold as a powder the usual formula is 5.10% D.D.T. mixed
with kaolin, which is china clay.