I.Lewis on mon 3 may 99
To: clayart=40lsv.uky.edu
From: ivorredhill=40yahoo.con.au
Date=3B Monday, 3 May 1999
Topic: Calcium Sulphide and other Noxics.( Noxious toxic substances)
I have been following this strand, wondering when someone would come up with
solid factual information. Are there no Encyclopedias of Chemistry out =
there? Do
Clay artists even know of their existence? Which reference books are made =
known
to students of ceramics at any level? My Science dictionary tells me that
Calcium Sulphide is sparingly soluble in water, that it smells of rotten =
eggs,
that it evolves Hydrogen Sulphide gas when reacted with acids, a gas which =
is
exceptionally poisonous, and dangerous, since it has an anaesthetic effect =
on
the sense of smell at levels of a few parts per million in the atmosphere.
For the life of me, I cannot see what value Calcium Sulphide would have in a
pottery or art studio unless used as a patination agent for metal =
sculptures.
Nor can I find reference to it in any of the Ceramic Text Books in my
possession.
A new compound was suggested recently, Cadmium sulphide. It seemed to be =
implied
that this was the chemical under discussion rather than Calcium Sulphide. I
thought Cadmium compounds had been replaced in formulations of colouring =
stains
and glazes although they are still essential compounds in Artist=92s =
pigments.
Again, as industrial compounds, Cadmium chemicals are know toxins. Their use=
and
disposal is under strict control in most developed industrial nations. My
chemistry text books tell me this element is on a par with Mercury when it =
comes
to toxicity.
I note Janet De Boos was cited as an authority on the Barium question. Well,=
as
a Graduate Chemist she is qualified to undertake the research needed in this
field and as a noted author of books about glazing going back over twenty =
years
she has the ceramic experience to support her opinions. Such expertise =
should be
valued by members of Clayart.
Best regards to all.
Ivor Lewis.
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