Fumes from burning borate esters?

[Pleiades]

I was browsing woelen’s page and I saw the page on green fire: http://woelen.scheikunde.net/science/chem/exps/borate_ester/index.html having some boric acid and some denatured ethanol around I gave it a try. After burning about 40ml in the dark (you have to see it for yourself, I mean green fire, awesome!), I turned on the lights and found the bathroom filled with a light ‘fog’, I noticed some sort of vapor coming off of the flames earlier too. Could this just be a light smoke? I used Ace Denatured Alcohol, which says it contains “Methanol, Ketones, Ethanol”. Any ideas on what this fog is?

[Darkblade48]

It could possibly just be smoke, or some incomplete combustion products.

 

Note that the borate esters are mildly toxic, so I don't suggest you breathe too deeply when you are burning boric acid in an alcohol.

[insane_alien]

just do it with some better ventilation in the future and you'll be fine.

[RyanJ]

It seems it could be trimethyl borate - a compound formed in the reaction that vapourises at 67 degrees C.

 

Not shure but it certainly seems like (Lets hope one of the experts can prodvide more insight)

 

Either way I agree - the stuff should not be inhailed if possible.

 

Cheers,

 

Ryan Jones

[Pleiades]

I was a bit freaked out when I turned on the lights and realized id been breathing the stuff without noticing it for a few minutes, I promptly opened the window and retreated. I should also mention that I was burning it in a shallow Pyrex cup, and the flames heated the liquid below to the point that it was boiling gently. It looked awesome, but yeah, ill be sure to do it in a well ventilated area next time.

[insane_alien]

seeing as your still typing i don't think you have anything to worry about from that lapse in safety.

[woelen]

The smoke that you obtain is very finely divided H3BO3 (or possibly B2O3). It is mildly toxic, but don't worry too much. The boric acid, or boric oxide, is formed on combustion of the barate ester, mentioned by RyanJ.

 

In your alcohol solution, you dissolved some H3BO3, but it is only a very small amount. From that part, you only breathed a minor fraction, so the total amount is minimal.

 

Next time, use a better ventilated place, but you do not have to worry from this one-time exposure.

[Pleiades]

Well, that clears that up, thanks woelen.