Emily & Kurt Kiewel on wed 18 oct 00
After all the discussion of the dangers of manganese dioxide as a gas I
spent some time looking through all my books for the boiling point. I
couldn't find any info on this. I found at least 4 different melting
points with differences ranging from 1042 C to 1640 C. Does anybody know
the boiling point of manganese dioxide? It must be higher than the melting
point, right?
Thanks-Emily Kiewel
Tom Buck on thu 19 oct 00
Emily K
My techbooks say there are four oxides of Manganese:
Mn(II)O, sometimes called manganese monoxide;
Mn(III)2O3, sometimes called manganese sesquioxide;
Mn(IV)O2, aka manganese dioxide;
Mn3O4, ie, Mn(II)O+Mn(III)2O3, natural hausmannite; and
possibly a trioxide that is postulated but difficult to isolate.
There is also Mn2O7 that has been generated but it explodes when warmed
to 95 C (but will begin to decompose at 55 C).
The one that is listed with the highest melting point is Mn3O4; it
is 1705 deg Celsius. The dioxide, MnO2 changes to MnO at 535 C. The
sesquioxide changes to MnO at 1080 C. The reference book has no figure for
the melting point of MnO, but one can assume that it is quite high.
The manganese oxide picture is affected by the presence of oxygen
in the kiln atmosphere: MnO2 may then combine with MnO to form the higher
melting material hausmannite, Mn3O4.
With such a complex mix of oxides, it is difficult to say whether
some of the manganese compounds will boil (go to vapour) during a kiln
firing, even one to C10. However, if you continuously use a lot of
manganese in glazes/clays, you should exercise great caution to avoid
contact with manganese compounds, both by skin cotanct and by inhaling any
fumes from the kiln.
Doctor B has just posted health data on manganese compounds and
the info is in the archives.
BFN. Peace. Tom B.
Tom Buck )
tel: 905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
ferenc jakab on thu 19 oct 00
> After all the discussion of the dangers of manganese dioxide as a gas I
> spent some time looking through all my books for the boiling point. I
> couldn't find any info on this. I found at least 4 different melting
> points with differences ranging from 1042 C to 1640 C. Does anybody know
> the boiling point of manganese dioxide? It must be higher than the
melting
> point, right?
The boiling point of manganese is 2235 degrees Kelvin (subtract 273 for
degrees C)
Feri
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