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OCR Page 1 of 220
THE DETECTION AND ESTIMATION OF RADIUM AND MESOTHORIUM IN LIVING PERSONS
by
Frederick B. Flinn (1), Howard H. Barker (2), and Herman Schlundt (3)
PEELIMINARY REPORT
INTRODUCTION
The ionizing power of alpha particles emitted from radioactive substances
has become the means of detecting and estimating extremely minute quantities
of radium and other radioactive elements. For example, a single alpha parti-
cle emitted from radium C produces fully two hundred and twenty thousand
(2.2 X 105, pairs of ions along its path in air over its range of nearly 7 centi-
meters. By means of sensitive electrometers or calibrated electroscopes the
very feeble ionization currents resulting from the emission of even a small
number of alpha particles may be accurately measured, and made the basis for de-
termining quantitatively the amount of the radioactive substance present in the sam-
ple of material under investigation. The finest of assay balances would be taxed
to its limit in detecting differences in weight of one microgram, but by means
of calibrated electroscope an experienced operator can determine quantitatively
one millionth of a microgram of radium- a micro-micro gram yupg or
To make this quantitative determinationsof such extremely small quantities
of radium, the amanation in equilibrium with the radium in the material under
malyais is separated, collected, and transferred to the ionization chamber of a
electroscope. From the observed increase in the rate of discharge
indicated by the fall of the charged leaf system--
tibese smell anounts of radium may be determined.
1. Professor, of Public Health, Columbia University, New York
2- Dalted States Badium Corporation, New York
3 Professon of University of Missouri, Columbie, Missouri
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