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Subject:
From:
Hervé Logé <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Wed, 2 Feb 2005 22:45:06 +0100
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> Re: oxalic acid:   Under high heat oxalic acid turns
> to formic acid
> (with the release of carbon monoxide - CO); so you
> may essentially be
> treating with formic if you're using the evaporator.

Lifted from the French Belgian list (Aug. 2004).
Original post from M. J-M Van Dyck below if you ever
want to check my free translation :

"
According to the Merck index, OA crystals have a
merging point around 101-102C. At this temperature, it
becomes a liquid and releases its water captured in
the crystalline structure. It also immediatly starts
its sublimation.

Temperatures higher than 60C would lead to OA
decomposition that completely occurs for 180C and
above, producing FA, CO2, CO and H2O.

Nevertheless, the temperature arises progessively and
the OA sumblimation is probably complete before the
vaporizer rises 180C. But it is not the case if the
vaporizer is not cool down before the next
utilisation.
"

As far as I remember, the heating temperature of the
varrox vaporizer is indicated in its user manual. It
is also written the beekeeper has to cool down the
vaporizer in water between 2 hives. Finally, white
crystals powder can be observed in hives after
sublimation. So if correctly done, it seems the
potential decomposition should not be cemplete.

Hervé


Texte original :

"
L'index Merck consulté ... il s'avère que le point de
fusion de l'acide
oxalique cristallisé se situe vers 101-102 degrés C.
Il libère alors son
eau de cristallisation et fond dedans, devenant donc
liquide. [...]
Une température supérieure conduirait à une
décomposition
qui arrive vers les 180 degrés et plus, produisant
divers composés tel
l'acide formique, du CO2, du CO et de la vapeur d'eau.


Bien entendu, il est probable que lors d'une première
sublimation, la
température s'accroit progressivement et tout l'acide
est sublimé bien
avant que l'appareil n'atteigne la température de 180
degrés.
Ce n'est plus le cas si l'on omet de refroidir
l'appareil pour l'opération
suivante.
"







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