Evening star. [volume] (Washington, D.C.) 1854-1972, 1936-12-24

Preparation in pure form and de-
termination Of the physical properties of
a liquid that may be a basic substance
of vegetable life Is reported by the
Bureau of Standards
The material is isoprene. 1t is one of
the simplest of all the known combina-
tions of carbon and hydrogen. its mole
cule consisting of five carbon atoms and
eight hydrogen atoms with the former
extended in the form of a chain. So
far as known, 1t does not occur uncom-
bined in nature. The isoprene on which
Norman Bekkedahl, Lawrence A. Wood
and Mieczyslaw Wojciechowski, Bureau
of Standards chemists. are working is
obtained by cracking" the more COM
pick molecules of terpenes obtained from
terpentine.
More than so years ago it was first
noted that rubber. heated to about 300
degrees centigrade, gave off various
vapors, one of which was isoprene. A
few years later it was recorded that when
isoprene was allowed to stand around
in laboratory at room temperature for
a month or more it changed from a
liquid with less viscosity than water to
a more and more viscous substance and
finally transformed itself to soft, sticky
mess almost indistinguishable from nat
ural rubber. 1t was long considered one
of the outstanding possibilities for the
making Of synthetic rubber. but the cost
of obtaining it is so great that such a
process never could be economically
sound.
The great significance of isoprene lies
IN the fact that many of the hydrocar-
bons which make up plant cells have
molecules which are exact multiples of
the isoprene molecule. They might have
been built up of bricks" of isoprene
which, 1t seems, may be one of the first
products of the universal process of
photosynthesis by which carbon dioxide
and water are converted into hydrocar-
bons in the living plant under the influ-
ence of sunlight-a process upon which
all life and earth depends.
1t Is significant that isoprene should
be so notable q constituent of latex, or
natural rubber. LAtex, it Is explained
at the Bureau of Standards, is not, ~
generally supposed, the sap of the rub
Der tree, although 1t Is obtained by tap
ping, much as maple trees are tapped.
It Is most abundant between the bark
and wood Of the tree and apparently is
composed Of q special kind of cells which
function as reserve from which the
organism can build up new cells of all
sorts in times of emergency.
Thus it has been found that latex is
much more abundant In rubber trees
growing in rich soil during the rainy
season and declines in times of drought
and when the food elements in the soil
are depleted, although the trees them
selves show no appreciable deterioration.
This has led to the theory that rubber
tree takes advantage of plenty to store
up lot OF molecules which it can absorb
and use In time of need.
Now, 1t Is explained, the latex mole
cule may be very extensive "polymeri-
ration" of isoprene molecules-perhap
several hundred of them strung to-
gether in long chain. It Is known that
the rubber molecule Is one of the largest
and most complicated of all the very
complex hydrocarbon molecules. Thus
the fact that it spontaneously gives Oh
isoprene and that isoprene spontane-
ously changes into rubber becomes Of
great significance as basic phenomenon
Of life. The isoprene molecules seem to
have an aversion to living alone and II
left alone hasten to form @polymers"
by binding themselves together in long
chains. Thus they constitute themselves
into the bricks" with which the rubber
tree can rebuild itself In case Of neces-