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Subject:
From:
Brian Fredericksen <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Mon, 5 Sep 2005 13:34:07 -0400
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I am interested in using Oxalic Acid for mite treatment and kept
running into conflcting information. So I asked a former colleague of
mine who is a PhD chemist for a large Fortune 500 company to look
into the use of OA for mite treatment.

The following is the response I received which I wanted to share with
the list:


Sorry it's taken me so long to respond to you--I know about oxalic acid
but not about treating hives with it, and I took the time to find out the
details.  Some of the bee-related Web sites that I checked out have
incorrect information; here are some facts.

The fact is that oxalic acid IS soluble in water, which means that it's
also soluble in honey.  It's slightly toxic to humans, but too much can
kill you in a very unpleasant way.  (Historical note: in Europe in the
1800s, oxalic acid was sometimes used as a poison (murder) and as
a method of suicide.  It wasn't pretty.)  That said, spinach is full of
oxalic acid and its salts (oxalates); it chelates or binds metal ions
such as calcium and iron.  Thus, the Popeye myth that spinach is a
good source of iron is just plain wrong: there is lots of iron in spinach
but it's tied up by the oxalic acid (it exists as the salt iron oxalate) and it
can't be absorbed by our bodies.  But spinach isn't at all bad for us.
It's extremely unlikely that OA would pose a toxicity hazard in your
honey.

You probably know that humans can taste only five things (that is, our
tongues have receptors for five tastes; everything else, we dectect with
our noses).  The five tastes are: sweet, sour, bitter, salt and unami
(unami is that taste of the Asian flavoring aid MSG, monosodium
glutamate).  Don't ask me why we have taste receptors for unami.
Things that taste sour are almost always acidic--vinegar (acetic acid)
is sour.  Citrus (citric acid) is sour.  Oxalic acid also tastes sour, which
doesn't bode well for your  honey if it gets contaminated with oxalic
acid.

But that begs the next question: what happens to OA that's sublimed
into a hive?  Good question, with an answer that you won't like: it
depends, and it's not possible to predict.  You know that sublimation
is the vaporization of a solid--a solid goes into the gas phase without
first melting to a liquid.  You've no doubt observed this yourself on a
very cold winter day when there are ice crystals on your car winshield
and they just disappear as you drive--they don't melt, they vaporize
(sublime).  Any vapor, water vapor or oxalic acid vapor, ultimately
condenses (in the case of OA, back to a solid) somewhere where it's
relatively cool.  Where is that in a hive?  I think that it depends on the
season, day, and time.  And on many other "bee factors" about which I
know nothing.  It is possible that a given hive has a perpetual "cold
spot" where the OA will continue to condense.  Over time, a lot of it
could build up there as a big crystalline mass, which might not cause
any harm unless it broke apart or dislodged and ended up someplace
where it could contaminate the honey or...I don't know.  It's also
possible that the OA vapor will distribute itself throughout the hive and
not build up in there at all.  So the bees, the comb, and the honey may
all contain small amounts of OA, which will be removed as bees die
and as you take the honey.  Probably not a big deal.  The upshot is that
oxalic acid probably doesn't pose a significant health hazard to your
hives if you sublime it into your hives.  If your honey got contaminated
with a toxic level of it, the honey would have a sour taste and nobody
would eat it.

The last important thing to consider it the hazard to YOU if you sublime
OA into the hives.  Breathing OA vapor would be a nasty experience, to
say the least, and it could be dangerous.  A deep breath of nearly pure
OA vapor would definitely do some damage to your lungs.  Maybe it's
no big risk if you have a couple of hives, but you've got so many that
you (or your workers) are at some risk if the wind is blowing or if the
OA is heated outside of the hives.  This is probably the most
hazardous aspect of using oxalic acid to control mites.  Keep in mind
that chemists sublime solids all the time, but we do it in a sealed
vessel--vaporizing from, for example, the bottom of the vessel and
condensing on the top of it.  We don't mess around and risk breathing
vaporized solids.  If you do it, BE CAREFUL.

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