Randy,

>>>You don't want to keep oxalic sugar water solution for more than a
few days even in refrigeration.
>What data do you base this recommendation on?  The study cited by 
Dave indicates that the refrigerated solution would not degrade to 
HMF almost indefinitely.

I guess I need to backtrack. :)  I do recall reading that oxalic acid 
solution should not be kept too long even in refrigeration.  However, 
the Swiss lab has looked into it and their work showed that, stored 
at 4C or colder, there will be a maximum of 22mg of HMF per kg of 
solution beyond some 48 weeks of storage.  

http://www.culturaapicola.com.ar/apuntes/sanidad/varroa/acido_oxalico_
rago_jarabe.pdf

Since this may be a safe level to the bees, it appears you can keep 
OA solution at =< 4C short term.

I treat once a year and I can treat all my hives in one day, it does 
not make sense to try to keep OA solution to the following year.

Thanks.

Waldemar

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