Clinch Valley news. [volume] (Jeffersonville, Va.) 18??-2019, 1921-12-02
RADIUM FOR DIALS AT $4,000
A GRAM.

If a thimbleful of radium costs
100000, how can manufacturers at
ford to use it for painting the dials
of $4.9S wrist watches? Does this
paint really contain radium? asks
an exchange.
The answer to these frequently
heard questions explains some of the
wonder of radium, for that metal is
used for this work, each dial COL.
tanning minute portion of real
radium. The fact that so infinitessi-
NAL quantity of radium rs is used
on watch dial is able to make tho
figures glow III the lark makes 1t
easier for the average person to ui.-
derstand how and why radium in
larger quantities is effective when
brought into contact with diseased
tissue by the medical profession
Luminous material seen on watch
and clock dials is combination of
radium and specially prepared zinc
sulphide. If one of these dials be
examined with good reading glass,
in the dark, after the eyes of tho
examiner have been in darkness for
about five minutes, the luminous
material will be seen to be seethins
with scintillations or tiny flashes Of
light. These flashes are caused by
the explosion of the atoms in tho
minute portion Of real radium in the
mixture.
"These atoms have been found To
be SO small that 250.000,000 of thenl
would probably be required to cover
one inch. AS each atom explodes h
particle flies from it as projectiie
from gun. These particles are too
} small to be seen by the most power
full microscope; but scientists have
found that when one of these parti-
Giles is suddenly stopped by striking
a crystal Of zinc sulphide the result
ing heat Is sufficient to make a flash
of light the eye can SEQ. Those are
the flashes seen under a good read
in" glass. These occur at tho rate OF
100000 a second on the averas !,
luminous watch bought In commerce
ial routine.
The brightness and durability of il
,,radium luminous dial depends on tho
number of these tiny flashes per
second. The more radium, the more
flashes and the brighter the dial. But
every flash means q blow upon a
crystal of zinc sulphide. These crys-
tails cannot stand these blows ill.,
definitely. They break under them,
and when this happens there are no
more flashes and the dial losses its
glow. The zinc has failed, not the
radium. Only one twenty-ffth Of epv
per cent Of any quantity Of radium
disintegrates or is lost in n year,
according to information given out
recently about the activities Of the
Standard Chemical Company, the or
ganization, which, to last April, had
produced more than half tho worlds
available supply of radium.
"From Ia dram of radium ION,
thimbleful) there are about 1874, 600.
100000 projectile-iike particles every
second. Crystals of zine sulphAie
would break down quickly If expos
ed to such bombardment. By re-
ducing the percentage of fradiun
until the number of these particle,
flying from the exploding atoms OF
the dial was about 200 900 n second
1t has been found that the dial would
have a brightness easily visible /,
darkness and for a period of f1y,
years. This means that the ouantit,
OF radium on the average dial can
not be more than about one miIiiontl
OF gram. and it is only about suci
minute quantity that is on Nh,
lfAverage dial"