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New Contributor

borax and alcohol

so I've been reading up and people are saying that to make green fire with borax or boric acid, then you need to mix it with menthol and then light it. will this experiment still work if I use rubbing alcohol instead?

(menthol:C10H20O isopropyl/rubbing alcohol:C3H8O borax:Na2B4O7 · 10H2O)(so the only difference between rubbing and menthol is they amount of atoms(c has 7 more atoms, and h has 12. should that really affect the experiment though?))

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New Contributor III

Re: borax and alcohol

Hi Ethan,

If you just want to see the green color that results when you put boric acid in a flame, you don't need a solvent at all. Just take a little boric acid powder on a spatula or on a loop of steel wire and put it in a blue flame from natural gas (a Bunsen burner or a gas stove gives a blue flame) You will see a nice green from the boric acid. The reason for using a blue flame is that it's easy on the eyes. If you use a yellow flame, from a candle for example, the yellow is pretty bright and it's harder to see the green from boron in boric acid. But use boric acid rather than borax (sodium tetraborate). The sodium in borax gives a bright yellow flame, and then you are looking for green from boron against a bright yellow from sodium. You can see the sodium yellow color by putting table salt, NaCl, on the spatula.

It's true that you can dissolve common chemicals in alcohols, put the alcohol solution in a small lamp, and see the metal colors in the flame when you light the wick.  But please, please Ethan, do it the "dry" way I show you below and don't burn any alcohol solvents! There is a real risk of burning yourself because alcohols (especially methanol, which used to be used in schools) are very volatile. You go to light the wick on the solvent ("spirit") lamp and it turns out that there's a cloud of alcohol vapor around the wick and you are putting not just your match but your whole hand in that and then you knock over the lamp when you draw your hand back. Teachers used to do this color demonstration because it was too dangerous for their students, but there are several cases where students 10 feet away would get burned and the teacher was burned badly, so we now do this without igniting any alcohol.

Here is the "dry" or no-alcohol way to see the colors. Take some popsicle sticks or Q-tips and soak them in distilled or de-ionized water to remove sodium, which gives the bright yellow flame (you can buy de-ionized water in supermarkets and drug stores; it's for steam irons). Dry them and put the dry stick in a blue flame to be sure that the flame doesn't turn too yellow; there's always some sodium salt in wood and cotton. Then make water solutions of boric acid and other salts, soak the popsicle sticks or Q-tips in those solutions, and dry them out. All your water solutions were colorless, right? Put the dried  and salted  popsicle stick in the flame and see the colors!

B in boric acid is green.

NaCl, table salt, is bright yellow.

Li in LiCl is red, but K in potassium chloride or iodide is lilac pink. A drug store can probably give you both.

Calcium is orange-red; find calcium chloride ice melter if you live in snow country or get calcium supplement pills at the drug store.

Strontium is bright red in a flame and barium is pale green. If you can't find salts of these near you (and maybe you should stay away from barium salts; they can be unhealthy), Anne Marie Helmenstine has a nice blog, "Colored Fire--Where to find Metal Salts for Colorants" at www.thoughtco.com.

Contributor III

Re: borax and alcohol

EXCELLENT detail on the spectrum experiment, Michael!  I also recommend that people view the available videos on the colors.  I know that is not quite as exciting or "hands on" as really doing the experiment, but it is very safe!

Best regards,

Steven

Contributor III

Re: borax and alcohol

Dear Ethan,

I think that Michael already provided the best answer.  ONE thing that I would note is to take particular care when reading or transcribing chemical terms.  The solution previously used was METHANOL, NOT menthol!  Yes, other alcohols would work as well (AND as DANGEROUSLY!!).  "Rubbing alcohol" would probably not work, as it is a 70% solution (sometimes less) of either ethanol or isopropyl alcohol, which may not be flammable.  A simple water solution is the best for all of the salts, which when dissolved can then be adsorbed onto wooden "craft sticks" and DRIED before using them to observe the salt emission spectral colors.

Whatever you do - experiementing is GREAT! - BE SAFE first of all!

Best regards,

Steven