Re: THORIUM MANTLES

["William Kolb" <William_Kolb_at_SETA@mail.hq.faa.gov>]

U.S. manufacturers began using Yttrium instead of Thorium in their mantles about
1991.  The tip-off is the yellow imprint on Yttrium mantles.  Thorium mantles
are imprinted with green.  The most recent mantles from India and Malta are now
imprinted with purple and still contain thorium.  All three types are available
in SEARS stores.  According to COLEMAN, Yttrium mantles are more rugged but the
light output is only about 85% that of a Thorium mantle--not a significant
difference.  Mantles are traditionally produced by dipping a nylon or silk mesh
bag into a solution of 95-percent thorium nitrate.  Other components of the
solution include beryllium, cerium, magnesium and silicon. After the bag is
coated, the thorium is converted to an insoluble oxide by exposing it to ammonia
vapors.  The mix of metals used in mantles is varied to acheive the best color
balance.  A typical Thorium mantle contains between 250 and 400 mg of Thorium-
232 and Thorium-228. 

bill
bkolb@arinc.com
_______________________________________________________________________________
Subject: THORIUM MANTLES
From:    radsafe@romulus.ehs.uiuc.edu at smtpgate
Date:    5/13/96  4:55 PM

I believe that the COLEMAN brand lantern mantles no longer contain thorium.
I bought several of them for demonstration purposes two years ago and
discovered that they weren't hot.  Another brand that was imported from India
did still contain thorium.  

Chris Hogan
University of Arkansas for Medical Sciences
Occupational Health and Safety
chogan@colan.uams.edu

My opinion only, standard disclaimers apply.