JUNE, 1952
289
RADIATIONS FROM RADIOACTIVE MATERIALS EDWARD ORBAN Mound Laboratory, Monsanto Chemical Company, Miamisburg, Ohio1
THE Mound
Laboratory of the Monsanto Chemical Company has supplied speakers on demand for any organization in Southwestern Ohio for the last five years. Since the Mound Laboratory is operated for the Atomic Energy Commission, the subject of the talks has been the various aspects of atomic energy, with the greatest call being for a discussion of civilian defense measures and the effects of atomic weapons. However, many groups have asked for a discussion of the more fundamental aspects. A small radioactivity demonstrator has been very useful in both types of lectures. It is not a new type of instrument, but has been marketed by several supply houses for a number of years. Most university laboratories have one on hand. The one used by Mound Laboratorv has been adaoted for laree audiences bv the addition or a larger glow lube backez by a flash buib reflector. A one-tube amplifier must be used in addition. to the demonstrator to give a large enough impulse to discharge the tube. A demonstration of aloha. . , beta, and eamma activitv can be made by mounting radiothallium, an& radiosilver sources directly on suitable backing materials. Copper and silver coins are very handy. 1t can be shown that alpha particles are blocked by a sheet of ~ a o e r beta . oarticles bv about an eiehth of an inch of aluminum, while an inch and a half of lead is required to block out gamma rays.
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U. S. Government contract No. AT-33-1-GEN-53.
Polonium may be obtained from the Eldorado Mining Company in Ottawa, Canada, and it is recommended that information on other radioisotopes be obtained from Dr. Paul C. Aebersold, Chief of the Isotopes Division of the Atomic Energy Commission in Oak Ridge. A number of radioactive minerals and ores and their sources are listed below. Most of them can be found on the shelves of a university geology department, or they can be obtained from Ward's Natural Science Establishment, Inc., in Rochester, New York. The betagamma emission from these minerals is so strong that the alpha emission cannot be distinguishedon the demonstrator. Uranium mes and minerals Pitchblende
gz2k ~~,,,,,h,,, r ~
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Samarskite Polyerase, Euxenite Euxenite mswnrt,hi+,~ -. .... . .....
Euxenite Antunite
Tnhrrni+n A " . , " . . "
wes and Monazite Sand Monoaite Sand Thorite Tlrorianite
Location Great Bear Lake Colorado Colorado Tvedestrand, Norway Mit,ch~ll ..... -... Connt,~. ",N C~ -. Mitchell County, N. C. Minas Geraes, Brazil Voandeloka, Madagascar H. ~ nntnrin I- .~..-. , .., Cnnrdn, . ,V. .-, . -... Hitero, Norway Hasardville, Conn. ~
Ra"rl.hll-"
calif
Bahia, Brazil Cleveland Countv. N. C. Madagascar Balangadn, Island of Ceylon
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A number of manufactured products either use radio-
290
activity or are radioactive. Static eliminators using a polonium strip are manufactured by The Nuclear Products Company, Costa Mesa, California. Thorium mantles for gasoline lanterns are readily available. Uranium colors for potteries are no longer used, hut samples may he found in stores handling old pottery and dishes. Uranium glass is used for sealing pyrex to metal. The Firestone Tire and Rubber Company until a few years ago manufactured a polonium spark plug which reportedly gave improved firing characteristics. Because of the relatively short half-life of polonium, the amount of radioactivity remaining may be so low that they can no longer display any alpha activity. The scintillation of zinc-cadmium sulfide phosphors
JOURNAL OF CHEMICAL EDUCATION
may be shown by painting the phosphor on the bottom of the inside of a Lucite tube. A strong alpha-ray source of 25 to 100 millicuries is brought close to the phosphor, and a glow may be observed in a partially darkened room. Under the proper conditions of lighting much smaller alpha-ray sources may be used. The dissipation of static electricity may be demonstrated by the use of the well-known cat skin, pithhall, and Lucite rod experiment for developing the static charge. If a radioactive source of fair intensity is brought into the vicinity of the pithballs, the static charge is shown to drain off immediately. Smaller sources take a longer time depending on the strength of the source.
