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polomadh 

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A question for any Chemists out there. Should sublimed apibioxil vapour (oxalic acid) be visible?

My Varroa treatments are all done now, and picking up a discussion from another thread about temperatures used to sublimate, this question still perplexes me.

I have it in my head that OA sublimation “vapour” was colourless.
Am I wrong, are the vapours I see steam from the breakdown of OA into CO2 and H2O? Or formic acid?

If so it as a result of my Anhydrous Apibioxil absorbing water and/or am I applying too much heat?
 

Apple 

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Possibly wrong ... but I thought the approved method for the application of ( overpriced) Apibioxall was to trickle over the colony in the deep midwinter... which causes the early death of the queen........???
Which is of no consquence as users woul be replacing the queen with a nice new imported one in the Spring ( if the colony survived that long!!)


Tin hat on!!!
 

jenkinsbrynmair 

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I have it in my head that OA sublimation “vapour” was colourless.
Am I wrong, are the vapours I see steam from the breakdown of OA into CO2 and H2O? Or formic acid?
It sublimates, turns into an invisible vapour, but as soon as it hits the cold air it desublimates and forms micro crystals, the 'steam' you see is just the OA turning back into crystals
 

Apple 

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A question for any Chemists out there. Should sublimed apibioxil vapour (oxalic acid) be visible?

My Varroa treatments are all done now, and picking up a discussion from another thread about temperatures used to sublimate, this question still perplexes me.

I have it in my head that OA sublimation “vapour” was colourless.
Am I wrong, are the vapours I see steam from the breakdown of OA into CO2 and H2O? Or formic acid?

If so it as a result of my Anhydrous Apibioxil absorbing water and/or am I applying too much heat?
I think JBM has answered this.....
However perhaps on another tack.... if sublimation temperature of OA it not important, why would the manufactures of the Sublimox device go to all the trouble of producing a temperature controlled device?
 

madasafish 

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I think JBM has answered this.....
However perhaps on another tack.... if sublimation temperature of OA it not important, why would the manufactures of the Sublimox device go to all the trouble of producing a temperature controlled device?

If heating OA in a confined space you can get a pressure build up of gas, temeratures rise in the pan and over c170C you can get formic acid (nasty).

With open pans, there is no pressure build up and so temeratures never get get high enough as the OA vapourises and moves away from the pan as it is as hot and rises. So no chance of formic acid.
 

jenkinsbrynmair 

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I think JBM has answered this.....
However perhaps on another tack.... if sublimation temperature of OA it not important, why would the manufactures of the Sublimox device go to all the trouble of producing a temperature controlled device?
You could ask why do BMW put indicators on their cars?
The average BM driver's answer would probably be 'Just because it's there, doesn't mean they're needed' :icon_204-2: :driving:
 

Apple 

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If heating OA in a confined space you can get a pressure build up of gas, temeratures rise in the pan and over c170C you can get formic acid (nasty).

With open pans, there is no pressure build up and so temeratures never get get high enough as the OA vapourises and moves away from the pan as it is as hot and rises. So no chance of formic acid.
But the Sublimox has a short copper nozzel open to the atmosphere and thus would be at ambient pressure Shirley?
 

Gilberdyke John 

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It's the same as steam - that is invisible until it hits cold air - look carefully at a boiling kettle and the first few inches as it escapes the spout is clear
 

madasafish 

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But the Sublimox has a short copper nozzel open to the atmosphere and thus would be at ambient pressure Shirley?
I would have thought ok. Shirley
 

Apple 

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...in equilibrium, yes. But when you first turn over the Sublimox there is an intial build up of pressure (that has been know to blast the cap off)
With the new Sublimox the cap is so looes you have to hold it in place!
 

gmonag 

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Sublimation of OA has nothing to do with Boyles Law. No sublimator pressurises anything. It is a simple matter of temperature.

If the GasVap crucible/Varrox pan/Sublimox is heated to >180C then the OA crystals dropped onto it, the OA will partially decompose to formic acid until the pan cools below 180C. The OA sublimates at 160C. The water in the OA Dihydrate crystals boils off at 100C.
 
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