Luminol volcano

Copper sulfate crystals make the luminol volcano erupt!

Difficulty:
Danger:
Duration:
10 minutes
Experiment's video preview

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

How long does the eruption last?

It usually lasts 1-2 minutes.

What is the gas that appears during the experiment?

This is oxygen, which results from the decomposition of hydrogen peroxide during the reaction.

What happens if I add more luminol to the vial?

Well, the more luminol you add, the less hydrogen peroxide you’ll be able to pour into the vial. So the reaction might be less intense. On the other hand, it will glow slightly brighter. You can try it out when repeating the experiment!

The volcanic eruption was nice, but a lot of solution spilled on the tray.

You can use the bundle of absorbents provided to absorb the spill.

How can I store the hydrogen peroxide bottle in order to repeat the experiment later?

You just need to close it with the lid. Insert its “leg” into the bottle nozzle. To avoid spilling, keep the bottle vertical. Leave it in the fridge (at +2/+15oC).

Step-by-step instructions

For this experiment, you will need:

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Luminol glows in a basic medium. To create this medium, pour some Na2CO3 into the vial.

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You will also need an oxidizing agent—hydrogen peroxide H2O2.

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When you add copper sulfate CuSO4, a catalyst, the oxidation of luminol begins, making the luminol glow. In addition, the mixture begins to foam as bubbles of oxygen O2 form.

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Expected result

Copper sulfate (II) CuSO4 facilitates two reactions simultaneously. First, hydrogen peroxide H2O2 decomposes vigorously and yields gaseous oxygen O2. The solution in the vial froths intensively, and the volcano starts erupting. At the same time, luminol oxidation takes place, which is witnessed as a deep blue glow in the dark.

Disposal

Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash with an excess of water.

Scientific description

Why does the solution in the flask start glowing?

galaxy_flask_3

Under certain conditions, luminol loses its electrons, i.e. luminol is oxidized, and that causes the glow. This experiment provides all the conditions for such reaction: hydrogen peroxide H2O2, sodium carbonate Na2CO3, luminol itself, and copper sulfate CuSO4, which we add in the very end.

Learn more

In the luminol oxidation reaction, copper sulfate acts as a catalyst, or a substance that is not spent during the reaction, but accelerates it. When dissolved in water, CuSO4 releases copper ions Cu2+, which then act as operating centers of the catalyst. These cations are able to accept one electron forming Cu+ cations:

Cu2+ + e → Cu+

And vice versa:

Cu+ - e → Cu2+

Thanks to this ability, copper ions catalyze luminol oxidation, which causes luminescence. The more of these ions are released, the more actively the reaction proceeds – so the glow is particularly bright near the pieces of copper sulfate.

Why does it froth, and why does the volcano erupt?

In this experiment, two reactions occur simultaneously: luminol oxidation, which leads to volcano luminescence, and hydrogen peroxide H2O2 decomposition affected by copper sulfate CuSO4. Hydrogen peroxide decomposition proceeds much more effectively near the pieces of CuSO4 that have enough time to slightly dissolve in water. Therefore, plenty of Cu2+ ions, which are responsible for the decomposition of H2O2, are available around these pieces in the solution.

The decomposition itself proceeds following a rather simple reaction:

2H2O2 → 2H2O + O2(gas)

Thus, oxygen is obtained, one of the two main components of air. Gas bubbles are collected around the copper sulfate pieces, where the reaction is particularly intensive making the bubbles jump out of the solution. Since the luminol oxidation reaction happens at the same time, the show is accompanied by a beautiful blue glow.

What is the role of hydrogen peroxide?

As in the other experiments of this set, hydrogen peroxide accomplishes two tasks in this experiment. The first task is luminol oxidation. Along with other products, this reaction produces light, quite a phenomenal matter consisting of many small particles called photons. The second task is creating gas bubbles: under the influence of copper Cu2+ ions, hydrogen peroxide decomposes releasing gaseous oxygen. The volcano erupts just because of it.

What is sodium carbonate needed for?

A specific environment in the solution must be maintained for hydrogen peroxide H2O2 to oxidize luminol. This environment can be created using sodium carbonate Na2CO3. Without it, only gas evolution occurs, with no glow.

What can be used instead of copper sulphate?

Many reagents can create a glow effect. To do so, they should exchange electrons (one by one!) with other reaction participants. Such substances include red prussiate of potash used in another experiment in the set, potassium permanganate KMnO4, and potassium iodate KIO3. All of them can also accelerate hydrogen peroxide decomposition reaction with release of oxygen bubbles.

How does it glow?

In the oxidation process, luminol molecule transforms into an ion with an intricate name "3-aminohydrophthalate":

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Importantly, this ion is in excited state, which means it carries excessive energy left after the reaction. Many processes yield products in excited state, but they usually release their energy to the environment through collisions with other molecules. In our case, product "relaxation" is quite different and unusual: it releases energy in form of light, a set of very fast small particles that we can see.

Follow up

Mix it all together!

When all the experiments are finished, we have three vessels: the flask, the beaker, and the vial. There are unreacted substances left in each of them: hydrogen peroxide, sodium carbonate, and luminol in the beaker; copper sulfate crystals in the vial; and a little bit of red blood salt in the flask.

We can mix them all together! Then the reactions, which began in the vial, will be able to proceed further. But you should do it in the dark, of course. After all, who doesn't want more glowing and hissing! First, pour the flask contents into the beaker. And now, pour everything from the vial into the beaker. Look how brightly CuSO4 crystals glow now!

By the way, everything that happens in the beaker is due to the same reactions of luminol oxidation and hydrogen peroxide decomposition you observed in the “core” experiments of the set. Luminol glows because of its oxidation, while bubbling and hissing is caused by oxygen O2 that evolves during the decomposition of peroxide H2O2.

That's interesting!

What is luminol used for?

As we already know, luminol can glow in the presence of iron found in blood. This feature proved to be useful in forensic science: the compound reveals minor traces of blood, even if the surface has been cleaned. This analysis can be done even years later! In such cases, the glow lasts for about thirty seconds and can be recorded using long-exposure photography.

Despite the obvious benefits of using luminol for finding clues, it is only applied as the last option. Unfortunately, while opening the proof for investigators prying eyes, luminol chemically reacts with the traces and destroys them.

Nevertheless, this method is indispensable in many situations. For example, blood on a red carpet, which is hard to notice with the naked eye, can be revealed with luminol. Further, it will help detectives to look for larger visible stains on a wooden floor covered by the carpet. However, luminol can also lead to a false trail, as the glow could occur due to the presence of small traces of copper, silver, bleach, urine, and even horseradish sauce.