Guess Which Chemical Was Used for This Green Flame?
The bright green flame is most commonly produced by boric acid dissolved in methanol. This combination yields a vibrant and pure green color during combustion. Other chemicals can also create green flames, but boric acid in methanol remains the most typical and effective choice in demonstrations and experiments.
Chemicals Producing Green Flames
- Boric Acid and Methanol: Boric acid, when dissolved in methanol, generates a striking green flame. Methanol burns nearly colorless, so the boric acid’s boron content distinctly colors the flame green. Ethanol, in contrast, tends to produce yellowish flames and does not highlight green color as clearly.
- Borax: Borax powder with flammable solvents like ethanol or isopropyl alcohol can also give green flames. However, the flame intensity and purity may vary compared to boric acid.
- Barium Compounds: Barium salts, such as barium nitrate, produce green flames as well. Barium is often used in pyrotechnics for this reason.
- Copper Compounds: Copper salts sometimes create green or bluish-green flames, but the color may differ from the bright pure green observed with boric acid.
How the Combination Works
Boron compounds emit green light when their electrons get excited during combustion. Methanol, serving as a clean-burning fuel, allows the boron emission to appear vividly. Mixing 10 g of potassium chlorate with 3 g of boric acid and a few milliliters of methanol can produce an impressive green flame when ignited with a small amount of sulfuric acid. This reaction releases energy and excites the boron atoms to emit green light.
Other Considerations
- Boric acid and its related compounds are preferred because they offer a relatively safe and bright green flame.
- Other options, like barium salts, present similar colors but carry different safety and toxicity concerns.
- Some guesses like uranium or thallium are mostly speculative or jokes and should be disregarded due to toxicity and rarity.
- Using colored food dyes or other additives is usually ineffective or produces dull colors in flames.
| Chemical | Flame Color | Notes |
|---|---|---|
| Boric Acid + Methanol | Bright Green | Clean, vivid flames; common in demonstrations |
| Borax + Ethanol/Isopropanol | Green | Less intense than boric acid combination |
| Barium Salts (e.g., Barium Nitrate) | Green | Used in fireworks; toxic |
| Copper Compounds | Greenish-Blue | Varies depending on compound |
Summary of Key Points
- Bright green flames often come from boric acid dissolved in methanol.
- Boric acid’s boron atoms emit green light under combustion.
- Other green flame producers include borax and barium salts.
- Methanol burns with little visible flame color, enhancing the boric acid’s effect.
- Safe and vivid green flames are harder to achieve with common household chemicals.
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