|
 In
2008, to treat 10 colonies, I
measured 250mL of sugar and 250mL of water. They weigh about the
same. When I mixed them, I got a little over 400 mL of syrup. That was the
most uncertain part of the task. I then calculated the correct
amount of dihydrate for 400 mL and mixed it up. It did not seem to
harm the bees and they did well in 2009.
From that mixing
experience, I conclude that to get around a litre of
syrup, 20% more, or 600mL of each sugar and water must be used.
To the resulting one litre
of 50/50 syrup, add 35 grams of oxalic acid dihydrate. The acid should
be weighed, since volume is variable. Pre-dissolving the acid crystals
in a small amount of water after weighing and before mixing into syrup
is recommended
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Here is the complete Canadian oxalic label.
(relevant excerpt below).
SOLUTION METHOD
NOTE: To completely dissolve
oxalic acid dihydrate, use warm syrup. Dissolve 35 g of
oxalic acid dihydrate in 1 litre of syrup made from a 1:1
sugar : water (weight:volume) mixture of sugar and water.
Smoke bees down from the top bars. With a syringe or an
applicator, trickle 5 mL of this solution directly onto the
bees in each occupied bee space in each brood box. The
maximum dose is 50 mL per colony whether bees are in nucs,
single, or multiple brood chambers. Under certain
unfavourable conditions, e.g., weak colonies, unfavourable
overwintering conditions, this application method may cause
some bee mortality or overwintering bee loss. |
Other resources:
| An email rec'd Nov 29...
> I've been working
on reconciling various OA formulas and was using your site
(Nov 18-19 2009 diary) to
figure the weight of 1:1 syrup. So I had to figure out the
cause behind your statement: "Well the best-laid plans... I
mixed as above and came up with 1,600 mL, not the expected
amount,..." on Nov 19. The cause was your calculation
4x400=1800 behind your statements in the previous paragraph.
Thanks. You are right. That explains
it.
> I had been
concerned that you were not getting consistent syrup weights
from mixing weighed ingredients. The underlying physics
appears consistent, so I am comfortable now.
> Another surprise is that the Canadian label produces a
much weaker solution than what Randy Oliver is recommending
on his web site. Randy's 1:10:10 by weight looks to me to be
nearly twice the strength you used.
There tends to be confusion between
the acid concentration in water and the amount of
dihydrate required to achieve it. The dihydrate already
has two water molecules attached, so a considerably
greater weight of dihydrate is required than would be
the case if pure acid were used. I am not aware of
sources of the pure acid, and there is no need to use
pure acid if the fact that the dihydrate contains water
is taken into consideration in the mixing.
|
A Persistent
Confusion
(note: The info below was corrected Dec 1/09)
There tends to be a
persistent confusion confusion between the actual resulting acid
concentration in water and the amount of the dihydrate required to
achieve it. This confusion is likely due to the fact that the
process has been developed by people with some chemical training and
is practiced by people who may be less conversant with chemical
matters, or who have been out of school a long time.
From Wikipedia
Oxalic acid is
the chemical compound with the formula C2O2(OH)2 or HOOCCOOH.
This colourless solid is a relatively strong carboxylic acid,
being about 3,000 times stronger than acetic acid...
Typically oxalic acid is obtained as the dihydrate.
(emphasis added)
As can be seen in the
figure below, the dihydrate contains two molecules of water
and weighs much more than the actual oxalic acid it contains. The
calculations below simply add up the weights of the atoms in each
and show how much of the weight in 86 grams of the dihydrate
crystals we buy is actually acid (90 g) and how much is water (36g).
Molecular formula
C2H2O4 (anhydrous)
Molar mass 90.03 g/mol (anhydrous)
Molecular formula
C2H2O4·2H2O (dihydrate)
Molar mass 126.07 g/mol (dihydrate)
From the above, we can see
that to get the same 90 grams of oxalic acid, 126 grams of the dihydrate crystals must be used, compared to
90 g of the pure stuff
-- thus the confusion.
Since the amount of
acid used is very small compared to the water in the syrup, the
'water of hydration' may be ignored when calculating the water
in the total solution, but since the water in the crystals is
insignificant compared to the total water in the syrup, but
since it is almost half the weight of the crystals, it must be
considered in measuring the acid.
Still confused?
Some very intelligent people get mixed up by this problem. It is a
good thing that there is a label that spells it out in simple terms.
Follow the label and all should go well.
Be sure to
double-check, though. You can see the obvious addition error I
made. Fortunately, it was minor, and in mixing the syrup, but
it shows how checking and rechecking can pay off.
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