Spot Plates

[FRAMEP@ORAU.GOV]

Hey Jim:

The ceramic spot plates I've seen are ca 4" x 6" x 0.5" (from
memory). They have about twelve circular depressions in them about an
inch across and a quarter inch deep. Usually they have a white glaze
but some are black. The black is from a uranium compound.

They are used for a variety of purposes (eg holding small samples of
whatever) but are primarily used to observe color changes or
precipitations in a titration type process. In high school I remember
(poorly) having starch solutions in each depression and adding spit,
oops, saliva, to each to break down the starch. A few drops of KI 
are added to see how much sugar had been produced. The KI turned the
sugar purple.  

Coors couldn't make beer during prohibition so they got into the
ceramics business. We have a Coors facility in town, a ceramics
facility that is. I suspect the black spot plates might be found in a
lot of chemistry labs.

Best wishes

Paul Frame