Evening star. [volume] (Washington, D.C.) 1854-1972, 1952-08-06
l ,000th BiIIionth
Of Gram Measured
British Atom Experts Report
On Radioactive Isotopes

Detection of as little as q thousandth
of billionth of gram now is possible
by use of radioactive isotopes.
This, together with various industrial
applications which have resulted from
atomic energy studies, have just been
reported by the British Atomic Research
Establishment at Harwell, whose work
in general runs nearly parallel to that
of the American Atomic Energy Com
mission.
This is a thousand times more senSi-
tive method of chemical analysis than
has existed in the past. It's special
use is for the detection Of minute i'm
purities.
The method is known as radioactiva-
ton analysis. A sample known to con-
tain minute impurity of some element
is bombarded with neutrons. Some of
the atoms become radioactive. The pro-
portion that would be formed by GER
tain amount Of bombardment is known.
The number actually formed can be
measured by counting the particles they
emit.
Industrial Applications.
Under favorable circumstances and
with the most favorable elements, the
report says, the scientists at Harwell
have been able to achieve the 1,000,.
00,000,0 00th of gram result.
With the next most sensitive method
the least that can be detected is O
1000, 000.0 00th Of a gram.
The British scientists have developed
q number Of industrial applications for
atomic measurements.
In the manufacture of textiles, it Is
explained, it is necessary to measure
the thickness Of an oil Aim spread over
very thin nylon f1bers. The measure
ment becomes possible by mixing with
the oil used in the process an extremely
small amount Of radioactive bromine.
A billionth Of a gram of oil on q
centimeter of fiber can be determined
by the extent to which the bromine
atoms darken a Photographic plate.
In another investigation the wear OF
cast iron bearings when improperly
fabricated was studied. The bearing
metal first was made radioactive in
the atomic pile and then the bearing
was allowed to run with various amounts
of oil. The amount of metal worn of
and washed away by the oil could be
determined from the consequent radio
activity of the oil, even though it
amounted to as little as q hundred
thouSandth of an ounce per quart of
oil. .... g..
Another industrial problem is to dis
cover the whereabouts of small leaks
in underground cables. in which gas is
maintained at a pressure to aid in the
insulation. This is being solved by mix
ing with the insulating gas radioactive
in oxvN1n hwy, TIM
atoms. The point at which gas Is leak
be determined with q radioactivity
detector.
Continuous Measure.
A method has been devised by which
the thickness Of materials can be
measured continuously. This depends on
the fact that beta rays-that Is,
electrons-are attenuated when they
pass through absorbing material to an
extent depending on the thickness of
the material. Radioactive calcium was
placed under moving belt of paper.
Above the paper is a So-called Geiger
counter which records each atomic
explosion. The number of counts per
second depends on the thickness Of
the paper.
Recent experiments have been made
at Harwell on another thickness
measure In which use is made of the
scattering of elementary particles. When
a stream of electrons falls on a metal
some of the particles will be scattered
backward in the direction from which
they came to an extent which depends
on the kind of metal. II the scattering
material consists of metal sheet
covered with thin layer Of another
metal, as is the case with tinplate. the
rust will depend on the thickness Of
the layer.