Peter Dillion asked:
> But whilst using Oxalic against Varroa, how and when would one
> treat against Acarine mites? Is it possible to use this acid in
> the presence of other materials, or is there going to be a
> reaction and therefore a result that is possibly detrimental
> to the colony/ beekeeper/ crop?
A very good question.
Neither is approved for use in the USA yet,
so I hadn't yet thought about it.
We who restore and rally old sports cars know that Oxalic
Acid is very good at removing rust from brake cylinders and
other metal parts, so this is not a "weak" acid at all.
One can reasonably conclude that something that takes rust
off metal will has some serious impact on anything it touches
in a beehive.
Since both Formic Acid and Oxalic Acid create fumes that
you are warned to avoid, and both are corrosives, it should
be obvious that the fumes of either will "burn" mucous
membranes and other "soft tissues".
But what in your hive could be considered "soft tissues"?
a) Eggs
b) Larvae
c) Newly-emerged bees, who's
exoskeletons are still soft
...and it appears that even adult bees have some
"soft tissues", since there is a risk of queen loss:
http://www.mitegone.com/forms/faq.pdf
"10. Should I expect queen losses when treating with Formic Acid?
Queen loses and damage to the hive were observed with the use of
85% acid and in colonies with old queens. With the use of 65% acid
and less than year old queens, we have experienced no queen losses
due to Formic Acid applications in six years. Keep in mind that
during the spring treatment, a lost queen can easily be replaced."
(I do not want to "pick on" the Mitegone folks. They should get
considerable credit for being honest about the risks of high
concentrations of acid. They even ask customers to sign a waiver
disclaiming any/all liability, which should be a big warning that
there is considerable risk involved. One can read it here
http://www.mitegone.com/forms/customerwaiver.pdf )
But you asked about Oxalic Acid.
Heating Oxalic Acid with a heating coil will first melt the
crystals, then boil the liquid and make a steam (vapor particles)
of Oxalic Acid solution, which is going to float around the hive,
land on things, and react with them. (By "react", I mean burn the
heck out of whatever it touches. By "burn" I mean that it is both
hot AND and acid, so it is two burns in one.)
This is much "worse" than the case with formic acid.
With formic acid, there are no superheated acid vapors.
The "shop towel approach" works at ambient temperatures.
The two chemicals are really very similar. In fact, Oxalic Acid
when it oxidizes, MAKES FORMIC ACID!!! To quote a standard
chemistry reference:
"Oxalic Acid - Decomposition products
include carbon monoxide & formic acid"
This makes me wonder how there would be much difference between
the two "treatments".
Formic Acid is one of the simplest acids you can find.
(Hey, if ants can make it, it must be simple.)
The equation for Formic is "H2C02" (the "2"s should be subscripted)
The structure looks like this (switch your font to courier if the
diagram below does not have the "O" directly above the "C", or
you will not be able to make sense of ANY of the following):
O
"
H-C-O-H
Everything is a "single bond", except for the Carbon-Oxygen bond,
which is a "double bond".
So, let's oxidize some Formic Acid, just like we did
on the blackboard in school...
HHCOO + 02 + (heat) => What?
We can rewrite this as:
HHCOO + OO + OO + (heat) => What?
Now, I gave you two O2s rather than one in the
line above, because I'm going to do a simple
"accounting" for how things combine:
HHCOO + OO + OO + (heat) => What?
COO 1 CO2 (Carbon Dioxide)
H OO 1 H2O (Water)
H OO 1 H2O (Water)
In the "accounting" above, I am showing where
each atom goes. (Chemistry is mostly bookkeeping)
Hey, that looks pretty harmless, doesn't it?
A little carbon dioxide and water never hurt anyone, did it?
Well, it IS going to hurt when it "steals" those oxygens
from you, rather than the air. That's the burning sensation
you get when you get a whiff of acid. It is oxidizing in
contact with YOU, and doing damage in the process.
Now let's look at Oxalic Acid:
The equation for Oxalic Acid is "H2C2O4", and the structure
looks like this:
O O
" "
HO-C--C-OH
So you have two carbons in Oxalic Acid, versus one in Formic Acid.
You also have two "double bonds" (between the Carbons and the Oxygens),
which is part of why you need a "hot plate" to break down Oxalic, and
don't need one to break down Formic Acid.
Let's play the same blackboard game with Oxalic Acid, given
that we know it will make Formic Acid and Carbon Monoxide:
H2C2O4 + O2 + (heat) => What?
H2C2O4 = HH CC OOOOOO => What?
H2CO2 = HH C OO = Formic Acid
CO = C O = Carbon Monoxide
O2 = OO = Oxygen
O = O = 1/2 an Oxygen
In the above, what happens to the "extra O"
that we are calling "1/2 an oxygen"?
It will combine with an "extra O" from a second
identical reaction to make a "full" oxygen.
(We should only write such equations with 2
Oxalic Acids and two oxygens, to have a "balanced
chemical reaction", but I'm not going to worry
about stoichiometry until I've had more coffee!!!)
So, what can we conclude from all this?
1) If Oxalic Acid's direct decomposition product is
Formic Acid, can we say that they work "the same"?
Nope, because we heated things up more
when using Oxalic, and we made tiny droplets
of liquid Oxalic Acid that got everywhere.
When using Formic, no superheated vapor is
going to be floating around.
2) Since Oxalic Acid breaks down into Formic Acid,
did we do twice as much "damage" to mites?
You could conclude that, since Oxalic Acid
will oxidize to Formic Acid, which will then
oxidize to CO2 and water.
3) But Oxalic Acid would then also "oxidize twice"
and hurt eggs, larvae, and newly hatched bees
"twice as much" as Formic?
Yes, you could say that. The bees can't
dodge the Oxalic Acid droplets. If one does
damage to the mites, one has a good chance
of also hurting bees.
4) Then why is anyone promoting Oxalic Acid? Why
not just use Formic Acid, and be done with it?
Good question! Oxalic Acid has a melting
point of 215 F, so it is a solid at room
temperature. Formic Acid has a melting
point of 47 F, so it is a liquid at room
temperature.
It seems that Oxalic Acid is simply a
"safer" way to transport "Formic Acid",
since until you heat it, it stays a solid.
Soilds don't "leak". Liquids can.
5) But I need to buy a "hot plate" to use Oxalic Acid...
Exactly. They sell you something, and
make money on the gizmo. They can't make
much money selling the acid, can they?
6) But what about reactions with other things I might
put in the hive at the same time, like menthol?
Oh, wow... have you seen the chemical equation
for menthol? It is C10H20O. That's ten carbons,
twenty Hydrogens and an oxygen. I'm not going to
try to diagram THAT in ascii characters!!!
7) But if I used Formic rather than Oxalic, won't I reduce
the risk of having an unexpected reaction, given that
I avoided one of the two oxidations, and completely
avoided introducing "super-heated vaporized particles"
into the hive?
YES!!!!
8) So why would anyone use Oxalic Acid?
Why not just use Formic?
Maybe because many beekeepers don't remember
their chemistry.
jim
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