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Re: Cerium Compounds

In the late 70's I had an undergraduate physics major try some gamma-ray
induced x-ray fluorescence experiments, and suggested he get some rare
earth material from chemistry, in order to get an x-ray significantly
different from lead.  He ended up using a sulfate, H4Ce(SO4)4, and I noticed
a lot of natural background gammas from a NaI spectrum.  It turned out to
be a typical spectrum from the Thorium series, most prominent being the
238- and 2614-keV gammas.  The student found that Ce is obtained typically
from monazite sands, which has lots of Thorium.  We then found that cerium
oxide is used as a glass polishing powder, and received a two pound sample
of Reopol #138 from Econ-O-Cloth, Inc. (and later a letter from Optical
Manufacturers International Ltd.) and indeed found it to be radioactive,
with a nice Thorium gamma spectrum.  My intention was to try to find
manufacturers of this material and see how much background radiation there
would be in their plants (this is a very fine powder), but never got around
to this.

My guess is that you have some natural Thorium in your sample, and you
should get a nice gamma spectrum with a NaI.

Tom Walkiewicz, RSO			walkiewicz@edinboro.edu
Dept. Physics				814-732-2468
Edinboro University
Edinboro, PA 16444