"So all of us using the ProVap at 230ºF are “sublimating" at too high a temperature ?!?"

Probably not. Some things to remember.  Chemistry does not "start to happen" at some distinct temperature like 189.5 deg F.  It starts to happen at or just above absolute zero.  Now, at that temp it might take a few billion or trillion years to break oxalic acid down to carbon monoxide, etc.  But nature is very patient.  Likewise it does not start to sublimate at 157 deg F.  It starts to sublimate just above absolute zero.  So, forget all about both of those exact temps.  They are highly misleading and tell you nothing at all. In fact anyone that states things like that obviously knows nothing at all about physical chemistry and should be ignored. 

What you need to know is not what temp something starts at but rather what is the ratio of the two things as a function of increasing temperatures.  Is there some temperature where sublimation is satisfactorily rapid and decomposition to things like carbon monoxide is satisfactorily slow given a length of time for the exposure?  Remember, both happen at all temperatures.  If sublimation is going to be practical there needs to be some temperatures where sublimation is fast relative to the decomposition into carbon monoxide.  I really do not care at all about decomposition into formic acid as we all know it will kill mites.  Obviously an acceptable temperature exists as many people are using sublimed oxalic acid to kill mites and those users have provided a lot of mite kill counts to show that sublimation is actually working very well.  In the ProVap the time that the oxalic acid is exposed to high temps is very short.  Only a few seconds.  A far shorter time than in pan sublimators.  The short time means there is very little time for decomposition to happen.  In fact, it is possible that you could lower the sublimation temperature while extending the sublimation time required and decompose more of the oxalic acid at the lower temp due to the longer time exposure.

We need to remember that in the fast sublimators the oxalic acid is sublimed very fast.  So fast that a couple of grams of oxalic hydrate knocks the temp of the sublimator down by more or less 30 degrees.  It seems rather obvious that the oxalic acid itself never gets close to 230 degrees F.  In fact very little, if any, can even hit 200 degrees F or it would not be able to cool the apparatus to that temp.  If you have used a ProVap you likely have noticed that as soon at the temp readout starts to rise from the minimum readout for all practical purposes 100% of the oxalic acid has sublimed.

We also should give the equipment supplier credit for having enough brains to do some testing to make sure the product he sells is effective if operated according to directions supplied.  Most vendors want their product to perform so they can get good advertising by word of mouth and thereby get more sales.  I have found the ProVap to work just fine when operated according to the directions and have zero reason to get creative and change the operation parameters which would run the risk of the treatment failing and a hive dying.  In fact, I suspect many mite treatments fail because the end user thinks he is smarter than the supplier and fails to follow the use instructions.  I have seen enough examples to be pretty sure I am right on this.  There are hundreds if not thousands of posts on the internet on ways to treat mites that I know do nothing at all to harm mites in any way.  But lots of people use them anyhow and wonder why their bees died.  Why not stick to proven stuff that is also legal and just follow the directions?  

Here is a data point to emphasize that temps are not all that important in an absolute sense and other things can be even more important than temperatures.   I have run oxalic acid thru a stainless steel tube that was red hot.  I would estimate a temp of roughly 600 deg C based on the tube color.  That translates to over 1000 degrees F.  I proved much of the oxalic acid survived the trip thru that tube.  Did any of it get to 1000 degrees F?  I doubt it.  Gas phase heat transfer is pretty poor.  And my residence time in the tube was fractions of a second.  But I am sure some was way about 230 degrees F and probably over 500 degrees F.

Dick

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