186 
in the process, making the total cost 
$1 per ton. The 1946 price of C14 
from the Manhattan District was 
about $400,000 per gram. 
The committee estimated that the 
market might pay about $10,000 per 
gram for C14 used in bulk organic 
chemicals, and $100,000 per gram for 
use in pharmaceuticals. 
Actual use, however, may develop 
unexpected advantages, and of course 
cost is bound to decrease as production 
increases. 
Another critical problem in produc- 
tion as distinct from laboratory use is 
the question of widespread distribution 
of all types of products and materials 
containing traces of radioactivity and 
the effect on sensitive materials such 
as photographic film, and on living 
things as a result of continual intimate 
exposure or possible ingestion by un- 
warned people or animals. Some 
believe that this problem will limit 
production uses to those isotopes with 
short half-lives of perhaps a few days. 
Then a period of storage of products 
before shipment could eliminate vir- 
tually all radioactivity. Such consid- 
erations may limit the list of possible 
tracers. For example, Ci4 has a 
half-life estimated at 6,000 years. Two 
other carbon isotopes, C10 and C11, 
have impractically short half-lives 
of 8 seconds and 20 minutes respec- 
tively. Thus no carbon radioactive 
isotope is known which could be used 
if radioactivity of the product is 
objectionable. Such questions can be 
settled only as experience and knowl- 
edge is gained and when proposed 
uses are specific rather than hypo- 
thetical. The need for elements with 
short half-lives either in production 
process or laboratory well may require 
a wide distribution of isotope-produc- 
tion facilities near industrial and 
population centers. 
It is also possible that experience 
will show that the amount of radio- 
activity required for tracer purposes 
in many products is so small that 
long-half-life tracers can be used 
widely in metallic, organic, and other 
ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
materials. Then industry may be 
faced with radioactivity in materials 
purchased for further processing, in 
scrap for remelting, and so forth. Such 
background radioactivity, if not con- 
trolled, might interfere with the further 
use of tracers. Thus in years to come 
materials specifications may be found 
containing minimum tolerances for 
radioactivity. 
The number of industrially impor- 
tant elements for which potentially 
useful radioactive isotopes, those with 
half-lives longer than a half day, are 
not known is quite limited but in- 
cludes oxygen, nitrogen, magnesium, 
aluminum, and silicon. 
There are some production uses 
which do not require presence ofthe 
radioactive isotope in the product. 
Included are separation processes 
where the radioactive isotope is one 
of the elements rejected, also processes 
involving catalysts. 
For example, in some oil-refining 
processes, a catalyst is diffused through 
a reaction vessel. Certain malfunc- 
tions may cause it to segregate or to 
emigrate from the vessel. If the cata- 
lyst were tagged with a radioactive 
isotope, its concentration and location 
could be registered continuously 
through the walls of the tank. 
RADIATION CHEMISTRY 
The infant field of radiation chem- 
istry relating to the use of radiation 
to produce or catalyze chemical re- 
actions is perhaps too new to warrant 
extending speculation very far. How- 
ever, the use of ultraviolet radiation 
to produce vitamin D in ergosterol is 
a well-known and related reaction. 
Doctors Franck and Burton (4) have 
examined the possibilities and re- 
ported to the United Nations the fol- 
lowing ‘“‘groups of processes where 
application of radiation chemistry 
appears promising”’: 
We may anticipate economic advantages 
in the vast field of polymerization processes 
which are now so successfully applied in the 
manufacture of plastics, rubber, and so 
forth; in this field, in fact, initial successes 
