6 replies to this topic

[fusion121]

I was reading through an old cheistry text book the other day and discoverd an amazing picture of bright green flames caused by the addition of boron (apprently not barium) to ethanol and then setting alight, it looks a really nifty effect. I'd rather not go to all the trouble of obtaining lots of diferent boron compounds to test so does anyone know the compound used in this effect (proably one with highest solubility in ethanol?).

[phildunford]

The classic demo of this is done with boracic acid. You can get this from chemists for use as an eye-wash I think!

Suspect it's hygroscopic and hence not used in solic formula.

[Phoenix]

Skylighter Bulletin 54 has some good pictures of coloured alcohol flames. mostly red (Li), but the green one was produced using boric acid.

Coloured Alcohol Flames

(PS, I don't know if it's also an eye wash, but boric acid is an antidote for wasp stings)

Edited by Phoenix, 16 January 2004 - 05:01 PM.

[Stuart]

Can you use metal carbonates to produce the colours?

[PanMaster]

Sounds like someone didn't revise chemistry . Let me enlighten you, any metal ion whatever it is barium carbonate or barium methanoate will make green in a flame or whatever colour it is. The solubility of carbonates in organics is another matter, I expect the more ionic potassium or sodium carbonates will be insoluble but the more covalent carbonates such as magnesium may be soluble.

Edited by PanMaster, 16 January 2004 - 08:43 PM.

[Gor]

Dissolve them in water, as concentrated as you can, then mix into the ehtanol max 20%. Boric acid doesnt dissolve so well. Copper Nitrate goives a good blue green and dissolves well.

I've got every colour including mauve, purple and orange, except pure blue. Tips of flames are often yellow which can be nice

ALso depends on whether you are burning pure ethanol or whether you use a wick. If you use a wick then you can sometimes just finely powder the salts and rub them in.

Don't use a carbon based wick. I sometimes use wire wool, or ceramic fiber.

I will eventually post some pictures (took some good nes at new year), but I'm snowed under with work

[Steve]

If you buy some boric acid, it is also usefull to add a few % to mixes of Aluminium and Nitrates, as it stops the reaction causing heating and that dodgy smell when water is added ( when making stars or, absorbed from the air). Making the mix safer (and perform better (theoretically))

Steve