# Oxalic Sublimation Temp?



## LanduytG (Aug 29, 2013)

When I was building my vaporizer I read you don't want it to get over 315 deg. Also make sure the Oxalic does not come in direct contact with the heating device. If you look at the ones you can buy, none of them have direct contact with the Oxalic.

Greg


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## VodoBaas1 (Mar 26, 2013)

At 315°F OA starts to sublime and will until it reaches 370°F at which point it will decompose to Formic Acid and Carbon Monoxide I believe. So, anywhere in between 315°F and 370°F, but when i made my OA vaporizer, I shot for consistent 330°F to 350°F.


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## Fishman43 (Sep 26, 2011)

Thank you.


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## frankthomas (Aug 2, 2012)

LanduytG and VodoBaas1, did you use plans from the net or your own design to build your vaporizers? Sounds like yours are electric. I built a simple one out of copper pipe and heat with a torch. If you have plans you could share I'd appreciate it.


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## LanduytG (Aug 29, 2013)

frankthomas said:


> LanduytG and VodoBaas1, did you use plans from the net or your own design to build your vaporizers? Sounds like yours are electric. I built a simple one out of copper pipe and heat with a torch. If you have plans you could share I'd appreciate it.


Sorry don't have any plans. I just looked at was being offered and then built one similar. All the heating element is, is a 12 volt glow plug for a diesel motor. If you were to go to NAPA and tell them you need a glow plug for a GM 6.2 or 6.5 it would cost you around $10.

Greg


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## Robbin (May 26, 2013)

Fishman43 said:


> I can find the melting point of oxalic acid (216-217 F), but what is the temperature that it sublimates to vapor for treating a hive?
> 
> Extra credit question: If it gets to hot it will break down into other acid(s), so what is the upper threshold temp before this happens as well?


When I bought mine I asked the manufacturer about this, there response was not to worry about it, The Oxalic acid would be completely sublimated before it could reach the temps that caused any problems.


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## crofter (May 5, 2011)

Do a couple of vaporizations outside the hive where you can see it. Time it from the time the OA quits boiling and starts to smoke and time how much longer it takes till it is all smoked off. You should probably cut the power about 30 seconds sooner and the heat stored in the vaporizer will coast it to complete vaporization without it ever reaching the unwanted breakdown conditions. The second reason to not over drive the temperature is that sometimes ladder comb wax can wind up in the cup and melt. No use to work up into the range of flash point of wax.


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## snl (Nov 20, 2009)

What one usually purchases is Oxalic Acid Dihydrate........

The water of hydration leaves at 101.5 degrees C. 
At 157 C degrees the OA starts to sublime (go gaseous) 
At 189 C what has yet to sublime, decomposes to formic and carbon monoxide.


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## VodoBaas1 (Mar 26, 2013)

I just looked at some that are offered out there and made my own. I used a block on aluminium from ebay and cut it to about a 4x4 block. I drilled a hole for the glow plug, a hole for a set screw to hold the glow plug and a hole for a handle. I then used a drill 1" drill bit to make the reservoir but I would use a bigger if you can find one. Ended up finding a CNC place to make the reservoir lager and they did it for cheap.


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## danno (Dec 17, 2007)

The Heilyser vaporizer uses a VW glow plug. It is a autolite #1104 and used on 90 & 91 Jetta's


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## little_john (Aug 4, 2014)

At standard atmospheric pressure:-
Oxalic Acid melts at: 102-3 C (216 F) 
Oxalic Acid sublimes at: 157 C (314 F)

... and that's it ! The only thing left in the pan will be a tiny amount of ash left from the very small percentage of impuriites in the commercial-grade product.

OA will NEVER reach it's decomposition temperature in an open vessel - only in a sealed, pressurised vessel such as might be found in a chemical plant. Once it reaches 157 ... it's gone.

I've made several from diesel glow-plugs and pieces of scrap copper (tubing and sheet) - they work extremely well. 

LJ


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## alfred westlake (May 16, 2008)

little_john said:


> OA will NEVER reach it's decomposition temperature in an open vessel


WHy do you think that?
WHat if the vaporizer metal is 400 or 500 F and the crystals come into contact with it? surely they will reach degrading temperatures before they are able to sublime.


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## little_john (Aug 4, 2014)

alfred westlake said:


> WHy do you think that?
> WHat if the vaporizer metal is 400 or 500 F and the crystals come into contact with it? surely they will reach degrading temperatures before they are able to sublime.


Context. I was referring to devices in which the temperature of the reaction vessel containing Oxalic Acid Dihydrate rises relatively slowly 'from cold', taking several tens of seconds to reach sublimation temperature - those were the only type of vapourisers in common use back in 2014. 
LJ


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## Robbin (May 26, 2013)

Of course you're right little john Alfred is using a strawman argument that's not relevant to standard bee keepers OAV devices. I've got 6 of different makes and models.


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