I am doing an experiment for a miticide for honey bees. I will be dissolving 600 g of 99.6 % oxalic acid in one liter vegetable glycerin at 150 °F. I have been told it will give off formic acid fumes while mixing and heating. I don't think it will until it get to the melting temperature of oxalic acid. Is there any safety concern? Also what would the shelf life of the mixture be?
You might want to raise the temperature a little bit as the reaction proceeds at 100-110°C to form formic acid. If the temperature is further raised to 260-280°C, then the reaction will proceed to form allyl alcohol.
Formic acid has almost unlimited shelf life if unopened and is protected from heat and light sources. Allyl alcohol is stable in normal storing conditions but it may polymerize into a thick syrup if left untouched for several years.
Here is a research paper for further reading.
Reaction sources: Google Images