Evening star., 1936-03-29

portant job, Is not to determine the
purity of a sample piece of radium
salt, but to discover exactly what its
gamma ray strength is. This is
measured with the new gamma ray
electroscope."
First, the test radium is placed on
a piece of gold leaf inside the device
and then the scientist peering in per-
feet safety at the sample from dis
tance of about 10 feet, snaps switch
that turns on an electric current
which charges the gold leaf, and as
the radiation, produced by the gamma
rays of the radium, goes through the
instrument in which the gold leaf is
hung, it makes the air conductor
and slowly discharges the electricity
on the gold leaf.
Since the leaf was held in an up
right position by the electric charge,
It will begin to fall as the charge leaks
of. The rate of fall is proportionate
to the strength of the gamma radia-
ton. This, as we hinted earlier, is
the bureaus major test for radlum
purity
A MOTHER novel device, used for a
"A somewhat similar purpose, is the
"emanation electroscope." Actually it
Is so sensitive that it enables the
scientist to measure one-thousano-
millionth of a gram of radium gas!
This apparatus is occasionally USED
to do special jobs for medical agencies.
For instance, to measure the exact
amount of radon" or radium. Their
average size is so microscopic that 1t
is entirely invisible, not only to the
naked eve, but under the ordinary
microscope.
When using the enanation electro
scope, first the specialist forces tiny
amount of the radium gas into the
device by means of a vacuum pump.
Whereupon the observer, armed with
a stop-watch, times the motion OF
piece of gold leaf inside the apparatus
in similar fashion as he does when
measuring q piece of radium salt IN
the bureaus gamma ray electroscope
HAVING shown you all these de-
vices, DR.. Curtiss now takes you
70 the basement of the east building
for a look at Americas queerest SAFE
Never does it house money, gold or
precious documents, but instead is
used exclusively to hold quantity
of radium barely the size OF tiny
cube less than three-eighths OF an
inch square.
Yet the door alone weighs 2,7OO
pounds, whereas the rest OF the safe
is heavy as lead, in fact, is lead-lined
6 inches throughout its structure.
WHY? Because lead shields the re-
search worker from the deadly radla-
tions of gamma rays.
DR.. Curtiss opens up the lotion
radium safe. He says it is the only
one of the kind in the entire world
and is another brain child" of the
Bureau of Standards technicians. If
necessary it would house a tenth OF
Americas entire radium supply, which
at a rough guess totals about 500
grams and is worth around $22,-
600 900.
You note with keenest interest the
compartments used for storage of the
arranged so that the scientist is ex-
posed to the rays from one compart-
ment at time only, and even then
q we'll within the safety range.
In front of each slide is lead block
2 inches thick. When all the slides
are closed the scientist has inches
of protective lead between himself
and all the radium in the safe, even
after he opens the outside door.
The radium itself is kept in small
wooden cases lined throughout with
half an inch of lead. The wood is
used because it protects the hands
against the dangerous secondary or
beta" rays.
This safe, by the way, is not the only
one used by the specialists. 1t is the
largest of three, and if necessary could
house so grams of radium. However,
the maximum amount ever kept in
side was grams.
The smallest safe is in the center
room, or main Office, of the bureau
technicians. 1t is about 3 feet by 21z
feet by 2. Ordinarily it contains about
200 milligramS, or two-tenths Of a
gram. This safe is not lead lined,
but contains lead plates for screening
off the dangerous rays.
The third, or medium-sized safe, Is
kept in an adjoining Office. 1t is
lined throughout with an inch Of
lead and at present contains no ra-
dium.
WHEN transporting sample Of
Nv radium from one room to an
other the Federal research worker
simply takes it out of the safe with
a pair of giant tweezers so built that
always the hands are kept 10 inches
away from the dangerous element.
Next he places it inside queer-look-
. ing wooden container which at first
glance resembles an average size
violin The lid is easily snapped on
and the radium can be carried about
In perfect safety until ready for test
ing.
The length and diameter of COM
mercial radium preparation are meas
ured as follows: First the bureau
scientist, with the aid of his safety
tweezers," drops the test metal into
q tiny, notch-shaped trough. Where
upon he goes into the next room, on
the opposite side Of the wall, and