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The ‘blue bottle’ experiment

In association with Nuffield Foundation

• Four out of five

Transform methylthioninium chloride (Methylene blue) from blue to colourless and back again by mixing it with glucose and shaking the solution, then letting it settle

An alkaline solution of glucose acts as a reducing agent and reduces added methylene blue from a blue to a colourless form. Shaking the solution raises the concentration of oxygen in the mixture and this oxidises the methylene blue back to its blue form. When the dissolved oxygen has been consumed, the methylene blue is slowly reduced back to its colourless form by the remaining glucose, and the cycle can be repeated many times by further shaking.

Source: Colin Baker

The reactions involved are not generally part of the curriculum, but this experiment has a number of features that make it ideal for investigating reaction kinetics - it is very quick, the chemicals are relatively cheap and safe, and the measurements are straightforward. It also has great visual impact and so is a good way of stimulating interest in chemistry, perhaps via an open day.

The demonstration lasts 3–5 minutes, but 15–20 minutes is needed for the preparation beforehand.

• Eye protection: goggles should be worn when preparing the solution
• Conical flask (1 dm 3 )
• Stopper or bung, to fit flask
• Potassium hydroxide (CORROSIVE, IRRITANT), 8 g
• Glucose (dextrose), 10 g
• Methylene blue (HARMFUL), 0.05 g
• Ethanol (IDA – Industrial Denatured Alcohol) (HIGHLY FLAMMABLE, HARMFUL), 50 cm 3
• Access to a nitrogen cylinder (optional)

Health, safety and technical notes

• Read our standard health and safety guidance
• Eye protection. Wear goggles when preparing the solution.
• Potassium hydroxide, KOH(s), (CORROSIVE, IRRITANT) – see CLEAPSS Hazcard HC091b .
• Glucose (dextrose), C 6 H 12 O 6 (s) – see CLEAPSS Hazcard HC040c .
• Methylene blue (HARMFUL) – see CLEAPSS Hazcard HC032 .
• Ethanol (IDA – Industrial Denatured Alcohol), C 2 H 5 OH(l), (HIGHLY FLAMMABLE, HARMFUL) – see CLEAPSS Hazcard HC040a .

Before the demonstration

Less than 20 minutes beforehand, preferably.

• Make a solution of 0.05 g of methylene blue in 50 cm 3  of ethanol (0.1%).
• Weigh 8 g of potassium hydroxide into the 1 dm 3  conical flask.
• Add 300 cm 3  of water and 10 g of glucose and swirl until the solids are dissolved.
• Add 5 cm 3  of the methylene blue solution. The exact quantity used is not critical.
• The resulting blue solution will turn colourless after about one minute. Stopper the flask and label it IRRITANT (due to the potassium hydroxide present).

The demonstration

• Holding the stopper securely in place, shake the flask vigorously so that air dissolves in the solution.
• The colour will change to blue and will fade back to colourless over about 30 seconds.
• The more shaking, the longer the blue colour will take to fade.
• The process can be repeated for over 20 cycles.
• After some hours, the solution will turn yellow and the colour changes will fail to occur.

Go beyond …

Beyond the ’blue bottle’ offers another spectacular colour-change-in-a-bottle demonstration, using indigo carmine to produce a range of stunning colours.

To confirm that oxygen is responsible for the colour change, nitrogen can be bubbled through the solution for a couple of minutes to displace air from the solution and the flask. If the stopper is now replaced and the bottle shaken, no colour change will occur. Reintroducing the air by pouring the solution into another flask and shaking will restore the system. Natural gas can be used (in a fume cupboard) if nitrogen is not available.

Some teachers may wish to present this experiment as a magic trick . The colour change can be brought about by simply pouring the solution from a sufficient height into a large beaker.

• A white background helps to make the colour changes more vivid. A white laboratory coat is ideal.
• On a cold day it may be necessary to warm the solution to at least 20°C, otherwise the changes are very slow.
• This experiment can be a popular open day activity. If visitors are to be allowed to shake the bottle themselves it might be wise to use a plastic screw-top pop bottle to eliminate the risk of the stopper coming off or the bottle being dropped and broken. The solution does not appear to interact with the plastic over a period of a day but it would be sensible to try out the bottle you intend to use beforehand.

Teaching notes

Methylene blue is a redox indicator and is colourless under reducing conditions but regains its blue colour when oxidised.

The removal of the blue colour is caused by the glucose which, under alkaline conditions, is reducing the methylene blue to a colourless form. Shaking the solution admits oxygen, which re-oxidises the methylene blue back to the blue form.

This experiment could be used to determine the kinetics of the reaction and thus the mechanism.  

The reaction is first order with respect to the hydroxide ion, methylene blue and glucose but zero-order with respect to oxygen. The rate law can be found by measuring how long it takes for a solution of known concentration to go colourless.  

The activation energy can be calculated using a normal Arrhenius plot - natural logarithm of the decolouration time (ln t ) against the reciprocal of absolute temperature (1/ T ). Campbell 2  explains this can be done because the rate of the slow step is independent of the oxygen concentration, and thus the time,  t , which is required for the total oxygen to disappear, is directly related to the rate constant,  k . A straight line is obtained from the plot of ln t  against 1/ T . The rate law for the reaction is: 3

Rate =  k [Dox][CH][OH-] 

where Dox is the oxidised (blue) form of methylene blue and CH is the carbohydrate, glucose. A simple mechanism for the reaction is: 

CH + OH- ⇌ C- + H2O

O2 + D → Dox (Fast)

Dox + C- → D + X- (Slow) 

where D is the reduced (colourless) form of methylene blue and X- represents the oxidation products from glucose (arabinoic, formic, oxalic and erythronic acids). The enthalpy of the reaction has been reported as 23 kJ mol-1. 

Using other redox indicators

Redox indicators other than methylene blue can be used to present other colours and make the demonstration really striking. In each case add the stated amount of indicator to the basic recipe of 10 g of glucose and 8 g of potassium hydroxide in 300 cm 3  of water. Mixtures of the dyes can also be used.

Phenosafranine  

This is red when oxidised and colourless when reduced. Use about 6 drops of a 0.2% solution in water for a bottle that goes pink on shaking and colourless on standing. The initial pink colour takes some time to turn colourless at first. A mixture of phenosafranine (6 drops) and methylene blue (about 20 drops of the 0.1% solution in ethanol) gives a bottle which will turn pink on gentle shaking through purple with more shaking and eventually blue. It will reverse the sequence on standing.

Indigo carmine  

Use 4 cm 3  of a 1% solution in water. The mixture will turn from yellow to red-brown with gentle shaking and to pale green with more vigorous shaking. The changes reverse on standing. These colours are those of traffic lights. Find the full equipment list and procedure for the Traffic light demonstration in the Colour chemistry activities. 

Resazurin  

IRRITANT – see CLEAPSS Hazcard HC032. Use about 4 drops of a 1% solution in water. This goes from pale blue to a purple-pink colour on shaking and reverses on standing. On first adding the dye, the solution is dark blue. This fades after about one minute.

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Additional information

This is a resource from the  Practical Chemistry project , developed by the Nuffield Foundation and the Royal Society of Chemistry.

Practical Chemistry activities accompany  Practical Physics  and  Practical Biology . 

The experiment is also part of the Royal Society of Chemistry’s Continuing Professional Development course: Chemistry for non-specialists .

© Nuffield Foundation and the Royal Society of Chemistry

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Specification

• Many chemical reactions are reversible.
• 1. know that many reactions are readily reversible and that they can reach a state of dynamic equilibrium in which: the rate of the forward reaction is equal to the rate of the backward reaction; the concentrations of reactants and products remain…
• In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called reversible reactions and are represented: A + B ⇌ C + D.
• Recall that some reactions may be reversed by altering the reaction conditions.
• 4.13 Recall that chemical reactions are reversible, the use of the symbol ⇌ in equations and that the direction of some reversible reactions can be altered by changing the reaction conditions
• C6.3.1 recall that some reactions may be reversed by altering the reaction conditions including: reversible reactions are shown by the symbol ; reversible reactions (in closed systems) do not reach 100% yield
• C6.3.1 recall that some reactions may be reversed by altering the reaction conditions including: reversible reactions are shown by the symbol ⇌; reversible reactions (in closed systems) do not reach 100% yield
• C5.2a recall that some reactions may be reversed by altering the reaction conditions
• C5.3a recall that some reactions may be reversed by altering the reaction conditions
• A reaction or process that releases heat energy is described as exothermic.
• Choice of indicator.
• Introduction to oxidation and reduction: simple examples only, e.g. Na with Cl₂, Mg with O₂, Zn with Cu²⁺.
• Oxidising and reducing agents.

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Blue Bottle Chemistry Demonstration

The blue bottle reaction is a classic color change chemistry demonstration. It interests students in chemistry, introduces the scientific method , and illustrates oxidation and reduction (redox reactions) and chemical kinetics. The reaction starts as a blue liquid which becomes colorless and returns to its blue color.

The usual materials for the Blue Bottle chem demo are:

• 8 grams potassium hydroxide (KOH)
• 10 grams dextrose
• Methylene blue solution (0.25 g methylene blue in 1000 mL water)
• 500-mL flask with stopper

You can make substitutions for the chemicals. In place of potassium hydroxide, you can use another strong base, such as sodium hydroxide (NaOH). Glucose may be used in place of dextrose. Several redox indicator dyes can be used instead of methylene blue. These include indigo carmine (green-red-green or green-yellow-red ), resazurin ( Vanishing Valentine ), thionine (purple), or FDC Blue #1 ( Gatorade and drain cleaner Blue Bottle demo).

The base solution (NaOH or KOH) can be prepared in advance, but it’s best to add the sugar and methylene blue just prior to the demonstration.

• In the flask, dissolve 8 grams potassium hydroxide in about 300 mL of water.
• After the solution has cooled, add 10 grams of dextrose.
• Add about 1 mL of methylene blue solution to the flask and stopper it. The ideal volume produces a solution that turns colorless upon standing, but becomes blue when the flask is shaken. If necessary, add more dye dropwise to achieve the desired effect.
• For the demonstration, shake the flask so that the solution is blue. Allow it to rest to turn colorless.

Exploring Chemical Kinetics

The Blue Bottle demonstration may be used to explore chemical kinetics. One variation on the demo is two use two 500-mL flasks, one with 2.5 g NaOH or KOH, 2.5 g glucose or dextrose, and 1 mL methylene blue and the other with 5.0 g NaOH or KOH, 5.0 g glucose or dextrose, and 1 mL methylene blue. Stopper and shake the flasks to start the reaction and compare the effect of concentration on the rate of the chemical reaction. Temperature also affects rate of reaction. KOH or NaOH solutions may be placed in hot and cold water baths before adding the sugar and methylene blue.

How It Works

Students can appreciate the blue bottle reaction and make predictions about its behavior if temperature or reactant concentrations change without understanding the chemistry. However, the reaction is well-studied. Dissolved oxygen oxidizes glucose to form gluconic acid. The sodium hydroxide converts gluconic acid into sodium gluconate. Methylene blue acts as an indicator, but also speeds the reaction by serving as an oxygen transfer agent. As it oxidizes glucose, methylene blue is reduced to form colorless leucomethylene blue. Shaking the stoppered bottle introduces fresh oxygen into the solution and reoxidizes methylene blue, returning it to its blue form. While the color change is reversible and the demonstration may be performed many times, eventually the solution turns yellow or brown.

Safety and Disposal

Avoid contact with the strong base and its solutions. Sodium and potassium hydroxide are caustic chemicals, capable of producing a chemical burn. As always, it’s best to wear safety goggles, gloves, and a lab coat (or similar forms of protective gear). The reaction neutralizes the base, so it’s safe to pour the solution down the drain. If you want, you can neutralize any excess base using a weak acid (e.g., vinegar) before disposal.

• Dutton, F. B. (1960). “Methylene Blue – Reduction and Oxidation”. Journal of Chemical Education . 37 (12): A799. doi: 10.1021/ed037pA799.1
• Engerer, Steven C.; Cook, A. Gilbert (1999). “The Blue Bottle Reaction as a General Chemistry Experiment on Reaction Mechanisms”. Journal of Chemical Education . 76 (11): 1519–1520. doi: 10.1021/ed076p1519
• Limpanuparb, Taweetham; Areekul, Cherprang; Montriwat, Punchalee; Rajchakit, Urawadee (2017). “Blue Bottle Experiment: Learning Chemistry without Knowing the Chemicals”. Journal of Chemical Education . 94 (6): 730. doi: 10.1021/acs.jchemed.6b00844

Related Posts

Blue bottle experiment

Experimental procedure, a) experiment with glucose, naoh, and methylene blue, b) experiment with glucose, cuso 4 and naoh, copy short link.

The Blue Bottle Chemistry Demonstration

When you shake it, the blue liquid turns clear and then back to blue

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In this chemistry experiment , a blue solution gradually becomes clear. When the flask of liquid is swirled around, the solution reverts to blue. The blue bottle reaction is easy to perform and uses readily available materials. Here are instructions for performing the demonstration, explanations of the chemistry involved, and options for performing the experiment with other colors:

Materials Needed

• Two 1-liter Erlenmeyer flasks , with stoppers
• 7.5 g glucose (2.5 g for one flask; 5 g for the other)
• 7.5 g sodium hydroxide NaOH (2.5 g for one flask; 5 g for the other)
• 0.1% solution of methylene blue (1 ml for each flask)

Performing the Blue Bottle Demonstration

• Half-fill two one-liter Erlenmeyer flasks with tap water.
• Dissolve 2.5 g of glucose in one of the flasks (flask A) and 5 g of glucose in the other flask (flask B).
• Dissolve 2.5 g of sodium hydroxide (NaOH) in flask A and 5 g of NaOH in flask B.
• Add ~1 ml of 0.1% methylene blue to each flask.
• Stopper the flasks and shake them to dissolve the dye. The resulting solution will be blue.
• Set the flasks aside. (This is a good time to explain the chemistry of the demonstration.) The liquid will gradually become colorless as glucose is oxidized by the dissolved dioxygen . The effect of concentration on reaction rate should be obvious. The flask with twice the concentration uses the dissolved oxygen in about half the time as the other solution. Since oxygen remains available via diffusion, a thin blue boundary can be expected to remain at the solution-air interface.
• The blue color of the solutions can be restored by swirling or shaking the contents of the flasks.
• The reaction can be repeated several times.

Safety and Cleanup

Avoid skin contact with the solutions, which contain caustic chemicals. The reaction neutralizes the solution, so it can be disposed of by simply pouring it down the drain.

Chemical Reactions

In this reaction, glucose (an aldehyde) in an alkaline solution is slowly oxidized by dioxygen to form gluconic acid:

CH 2 OH–CHOH–CHOH–CHOH–CHOH–CHO + 1/2 O 2 --> CH 2 OH–CHOH–CHOH–CHOH–CHOH–COOH

Gluconic acid is converted to sodium gluconate in the presence of sodium hydroxide. Methylene blue speeds up this reaction by acting as an oxygen transfer agent. By oxidizing glucose, methylene blue is itself reduced (forming leucomethylene blue) and becomes colorless.

If there is sufficient available oxygen (from the air), leucomethylene blue is re-oxidized and the blue color of the solution can be restored. Upon standing, glucose reduces the methylene blue dye and the color of the solution disappears. In dilute solutions, the reaction takes place at 40 degrees to 60 degrees Celcius, or at room temperature (described here) for more concentrated solutions.

Other Colors

DragonImages / Getty Images

In addition to the blue/clear/blue of the methylene blue reaction, other indicators can be used for different color-change reactions. For example, resazurin (7-hydroxy-3H-phenoxazin-3-one-10-oxide, sodium salt) produces a red/clear/red reaction when substituted for methylene blue in the demonstration. The indigo carmine reaction is even more eye-catching, with its green/red-yellow/green color change.

Performing the Indigo Carmine Color Change Reaction

• Prepare a 750 ml aqueous solution with 15 g glucose (solution A) and a 250 ml aqueous solution with 7.5 g sodium hydroxide (solution B).
• Warm solution A to body temperature (98-100 degrees F). Warming the solution is important.
• Add a pinch of indigo carmine, the disodium salt of indigo-5,5’-disulphonic acid, to solution A. Use a quantity sufficient to make solution A visibly blue.
• Pour solution B into solution A. This will change the color from blue to green. Over time, this color will change from green to red/golden yellow.
• Pour this solution into an empty beaker, from a height of ~60 cm. Vigorous pouring from a height is essential to dissolve dioxygen from the air into the solution. This should return the color to green.
• Once again, the color will return to red/golden yellow. The demonstration may be repeated several times.
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The Blue Bottle Demonstration

A bottle containing a colorless solution is shaken and instantly turns blue. The blue bottle is left to sit for a few minutes and returns to a colorless state. If shaken again, the bottle will again become blue.

In the presence of OH-, glucose is converted to gluconic acid. This reaction provides H+ and 2e-, which act to convert methylene blue from it’s oxidized (blue) form to it’s reduced (colorless) form. When the bottle is shaken, O2 from the upper portion of the bottle is associated into the solution. This causes an oxidation of the reduced form of methylene blue, re-creating the blue color. If left to sit, the O2 will come out of solution and the reduced form of methylene blue will be re-created.

Blue Bottle Experiment

Introduction: Blue Bottle Experiment

Hi there!. This is a simple experiment. There is a bottle contain a liquid like water. When it shake, that liquid turns blue color. Just try to do it.

Chemicals that we are using in this experiment are easy to find.

• Sodium hydroxide

Methylene blue (This chemical can be found from stores that sell aquarium fish.)

A volumetric flask

if you don't have a flask, you can use a bottle. (glass or plastic)

first get 1 gram of sodium hydroxide.(if you don't have a scale, just get a very little amount.) now dissolve it with about 20ml of water. (cold water is better)

Not get 5 grams of glucose and mix with 40ml of water. Then add few drops from methylene blue and mix it again. Then add it to the flask. (or bottle)

This is the final step. now add sodium hydroxide solution to the flask and mix it. Now wait for a few seconds.

after few seconds the solution turns colorless. Now shake the bottle. It turns blue. and again after few seconds the solution turns colorless.

I think you were enjoyed. Please visit my website to more experiments. www.coolsciencepage.blogspot.com

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The Blue Bottle Experiment Explained

The famous blue bottle experiment a visually dramatic way to teach reduction-oxidation (redox) chemistry. Students from grade school to grad school find this reaction memorable and it is considered a classic staple in chemical demonstration shows. A half-full bottle of colorless liquid turns blue when shaken, and when the bottle is allowed to sit still, the color fades. Shaking the bottle again causes the color to reappear like magic! What’s going on?

On the molecular level, the blue bottle experiment is a complex system composed of ethanol, the simple sugar glucose, the dye methylene blue, the hydroxide ion, and oxygen from the atmosphere. The color change occurs do to a pair of competing reduction-oxidation reactions. Hence, the blue bottle experiment is a wonderful tool for introducing the key concepts of reduction and oxidation.

All redox reactions involve electrons being transferred from one compound, the reducing agent, to another compound, the oxidizing agent. The term “reduction” means “gain of electrons”. This seems like an odd choice of terminology since “gain” and “reduce” are usually considered antonyms. However, because the electron has an electrical charge of negative one, gaining electrons will reduce the charge of a species. The term “oxidation” means “loss of electrons” and often, but not always, involves reaction with oxygen. A common mnemonic is the phrase OIL RIG, which stands for “Oxidation Is Loss, Reduction Is Gain”.

In first stage of the blue bottle experiment, the methylene blue dye acts an oxidizing agent and the glucose acts as a reducing agent. The methylene blue oxidizes the glucose to gluconic acid and the glucose reduces the methylene blue to its colorless form. The result is a bottle of colorless solution.

When the bottle is shaken, the surface are of the liquid temporarily increases, causing more oxygen to dissolve in the ethanol. The additional oxygen acts as an oxidizing agent and changes methylene blue to its blue, oxidized form. The result is a dramatic color change from colorless to blue.

When the shaking is stopped, the oxygen levels in solution begin to drop. With less oxygen present, the methylene blue once again is reduced to its colorless form by the glucose, and observers will see the color fade and disappear. The color change can be repeated many times simply by shaking the bottle to induce the blue color and then allowing it to sit still in order to make it disappear.

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Change a solution’s color with a shake of your hand!

Sodium hydroxide

• Methylene blue
• Put on protective gloves and eyewear.
• Conduct the experiment on the plastic tray.
• 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.
• 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.
• 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

Don’t worry! Continue with the experiment. The experiment will work with more methylene blue, but the solution will take longer to become colorless.

Yes! Just put the flask into a bowl of warm water (but don’t forget to close it with the stopper first!). The higher the temperature, the faster the liquid will lose its blue color.

Everything’s fine – the solution is simply too hot. Wait until it cools a little and then shake the flask again. The lower the temperature, the slower the solution will lose its blue color.

Try adding some more of both the glucose and NaOH solutions.

The solution stops turning blue when there is no more oxygen in the flask to oxidize the methylene blue. Just remove the stopper and let some air in, then put the stopper back, hold it in place, and shake the flask. The liquid will turn blue again.

The blue bottle will work as long as the flask contains oxygen and glucose. You can remove the stopper to let some oxygen in and add some more glucose. You can also use any household source of glucose instead of the glucose solution from the set, such as maple syrup, honey, or berry or fruit syrup. Please note that table sugar (sucrose) isn't suitable for this experiment. You can use this reaction to experiment with different sweet syrups and jams and figure out which of them contain carbohydrates that methylene blue can oxidize!

Step-by-step instructions

First, make a solution containing a reductant (glucose) and methylene blue.

Now add some NaOH to make the solution basic.

Methylene blue takes some electrons from the reductant, glucose, and turns colorless. You didn't add it intentionally, but the solution contains a powerful oxidant—oxygen. Oxygen can take electrons from methylene blue, making it blue again. But once all the oxygen in the solution is used up, the methylene blue stays colorless.

Even though the solution is now devoid of oxygen, the air in the flask still contains some. Just shake the flask to dissolve it and see what happens.

Expected result

Blue solution in the flask becomes colorless. Shaking the flask turns the solution blue again!

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

Scientific description

Why does the solution become colorless.

Initially, the solution contains the components for a potential chemical reaction. Glucose itself is more than happy to surrender its electrons. The oxygen dissolved in the water would be delighted to accept these electrons. Interestingly enough, though, oxygen isn't that willing to interact with glucose. And methylene blue can help: this colored compound acts as a carrier in our experiment, taking electrons from glucose and passing them to oxygen. However, at a certain point, the oxygen in the solution runs out, leaving methylene blue in an awkward position: it’s taken electrons from glucose, but has nowhere to pass them on to. When this happens, methylene blue cannot turn blue anymore and has no choice but to stay colorless.

Methylene blue:

Why does the solution turn blue again?

We can saturate the solution again with oxygen from the air above the solution. When the flask is shaken, oxygen from the air dissolves in the solution. The reaction can then proceed until all the oxygen available in the solution is spent again. However, this trick cannot be repeated endlessly. Since the flask is tightly sealed, sooner or later all the oxygen from the air will be depleted, and the solution will then remain colorless even when shaken. Nevertheless, the process can be reactivated by opening the flask to let some more air in.

Why did we add an alkali to the glucose aqueous solution?

By adding sodium hydroxide NaOH aqueous solution, we created an alkaline environment. Methylene blue needs an alkaline environment in order to accept electrons from glucose; otherwise, the reaction will not proceed, and the solution will remain blue. You can check this condition by conducting the experiment without NaOH.

Why is it so important to seal the flask tightly?

First and foremost, you’ll be able to shake the flask without sending any liquid flying.

Moreover, in sealing the flask we are preventing ambient air from entering, and ensuring that the oxygen in the ambient air will not have access to our solution either. This is why the color can only be restored by shaking the flask (see Why does the solution turn blue again? ). The most diligent observers may notice that the blue tint doesn’t disappear completely after the first shake, but remains at the border between the solution and air in the flask (along the so-called meniscus ) and forms a nice blue fringe. The same would happen if the flask were left open. This is caused by a high concentration of oxygen present in the air above the solution. The oxygen permeates the liquid-gas interface and converts methylene blue to its colored form. However, as the oxygen supply in the flask is gradually depleted, this border gets increasingly thinner and finally disappears.

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Photochemical & Photobiological Sciences

Blue bottle light: lecture demonstrations of homogeneous and heterogeneous photo-induced electron transfer reactions.

* Corresponding authors

a Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, UK E-mail: [email protected]

The classic, non-photochemical blue bottle experiment involves the reaction of methylene blue ( MB ) with deprotonated glucose , to form a bleached form of the dye , leuco-methylene blue ( LMB ), and subsequent colour recovery by shaking with air. This reaction is a popular demonstrator of key principles in kinetics and reaction mechanisms. Here it is modified so as to highlight features of homogenous and heterogeneous photoinduced electron transfer (PET) ( Pure Appl. Chem. , 2007, 79 , 293–465) reactions, i.e. blue bottle light experiments. The homogeneous blue bottle light experiment uses methylene blue, MB , as the photo-sensitizer and triethanolamine as the sacrificial electron donor . Visible light irradiation of this system leads to its rapid bleaching, followed by the ready restoration of its original colour upon shaking away from the light source. The heterogeneous blue bottle light experiment uses titania as the photo-sensitizer, MB as a redox indicator and glucose as the sacrificial electron donor . UVA light irradiation of this system leads to the rapid bleaching of the MB and the gradual restoration of its original colour with shaking and standing. The latter ‘dark’ step can be made facile and more demonstrator-friendly by using platinised titania particles. These two photochemical versions of the blue bottle experiment are used to explore the factors which underpin homogeneous and heterogeneous PET reactions and provide useful demonstrations of homogeneous and heterogeneous photochemistry.

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A. Mills, K. Lawrie and M. McFarlane, Photochem. Photobiol. Sci. , 2009,  8 , 421 DOI: 10.1039/B821222H

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Varianten des Photo-Blue-Bottle Experiments

10 Varianten des Photo-Blue-Bottle-Experiments

Photo-Blue-Bottle - Basisexperiment

Im Video wird das Photo-Blue-Bottle Experiment in einer Basis-Version gezeigt.

Photo-Blue-Bottle - Erweiterungsexperiment Luft

Im Video wird gezeigt, dass die Luftmenge einen Einfluss auf die Rückfärbung beim Schütteln der Photo-Blue-Bottle-Lösung hat.

Photo-Blue-Bottle - Erweiterungsexperiment Wellenlänge

Im Video wird gezeigt, dass nur Licht einer bestimmten Wellenlänge einfluss auf die Photo-Blue-Bottle-Lösung hat.

Photo-Blue-Bottle - Erweiterung Wärme

Im Video wird der Einfluss von Wärme auf die Photo-Blue-Bottle-Lösung gezeigt.

Photo-Blue-Bottle - Konzentrationszelle

In dem Video wird der Photo-Blue-Bottle-Versuch in einer galvanischen Zelle gezeigt. Beide Halbzellen sind gleich aufgebaut und enthalten die gleiche Lösung. Durch Bestrahlung einer Zelle mit Licht wird eine Spannung aufgebaut, die nach Einleiten von Luft in die bestrahlte, blaue Lösung wieder zusammenbricht. Der Spannungsunterschied wird mit einem Komparator verdeutlicht.

Photokatalytische Herstellung von Wasserstoff mit dem PBB-System in der Zweitopfzelle

Im Video wird die photoelektrochemische Herstellung von Wasserstoffgas in einem Zwei-Topf-Aufbau gezeigt. Dazu wird die Photo-Blue-Bottle-Halbzelle mit Licht der Wellenlänge 450 nm bestrahlt, sodass photochemisch angetriebene Redox-Zyklen durchlaufen werden, die in der zweiten Halbzelle zur Reduktion von Protonen zu Wasserstoffgas führen. Das Wasserstoffgas wird anschließend in einer modifizierten Knallgasreaktion identifiziert.

Photochemische Wasserstoff-Herstellung mit dem PBB-System in der Eintopfzelle

Im Video wird die photoelektrochemische Herstellung von Wasserstoffgas in einem Ein-Topf-Aufbau gezeigt. Dazu wird die Photo-Blue-Bottle-Lösung mit einem Katalysator versetzt und mit Licht der Wellenlänge 450 nm bestrahlt. Das Wasserstoffgas wird anschließend in einer modifizierten Knallgasreaktion identifiziert.

Photoelektrochemische Reduktion von Methylenblau mit dem PBB-System

Im Video wird gezeigt, wie Methylenblau elektrochemisch in einer Halbzelle zu Leukometylenblau reduziert wird, wenn die andere Halbzelle, gefüllt mit einer Photo-Blue-Bottle-Lösung bestrahlt wird. Die Leukomethylenblau-Lösung wird anschließend durch Rückoxidation mit Luftsauerstoff wieder blau gefärbt.

Experimentierset "PHOTO-CAT"

Experimentierset PHOTO-CAT mit Experimentieranleitungen (online)

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Workshop „Lichtlabor Pflanze und künstliche Photosynthese“

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Artikel zu verschiedenen Varianten des Photo-Blue-Bottle Experiments in chronologischer Reihenfolge ab 1994

Hinweis: Die neuesten Artikel befinden sich ganz unten in dieser Liste.

Photo-Blue-Bottle – Modellversuche zur Photosynthese und Atmung, M. Tausch, PdN-Chemie, Heft 3, 1994

In dieser Erstveröffentlichung des Photo-Blue-Bottle Experiments wird die PBB-Lösung auf dem Tageslichtprojektor oder im UV-Tauchlampenreaktor bestrahlt. Die Phänomenzyklen gelb-blau-gelb und die damit verbundenen Redoxreaktionen als Modell für den Kohlenstoffkreislauf bei der Photosynthese und Atmung stehen werden experimentell und konzeptionell erschlossen. Es wird großen Lösungsvolumina von einigen Hundert Millilitern gearbeitet. Die PBB-Lösung enthält giftiges Methylviologenen.

Der Artikel kann hier aufgerufen werden.

Kreislauf des Kohlenstoffs in der Biosphäre – ein Modellexperiment, S. Korn, M. W. Tausch, PdN-ChiS, Heft 7, 2000

Das Photo-Blue-Bottle Experiment wird in diesem Artikel erstmalig in der Variante als photoelektrochemische Konzentrationszelle beschrieben. Damit kann neben den Stoffkreisläufen auch die Energiekonversion und –speicherung beim Kreislauf Photosynthese/Atmung experimentell demonstriert und konzeptionell erklärt werden. Es wird immer noch mit relativ großen Lösungsvolumina, starken Lichtquellen (UV-Tauchlampen oder Ultravitalux-Lampen) und mit giftigem Methylviologen gearbeitet.

Photokatalyse – reif für den Chemieunterricht, M. W. Tausch, PdN-ChiS, Heft 1, 2011

Das Photo-Blue-Bottle Experiment liefert exzellente Beispiele für homogene und heterogene Photokatalyse. Die im Vergleich zu den vorangegangenen Arbeiten ergänzten und modifizierten Varianten des Experiments, beispielsweise der Einsatz von Titandioxid als Photokatalysator, verwenden immer noch Methylviologen als Modellsubstanz für Kohlenstoffdioxid.

Akku leer? Licht an! – photoelektrochemische Lichtenergiekonversion und -speicherung, M. W. Tausch, C. Bohrmann-Linde, F. Posala, D. Nietz, PdN-ChiS, Heft 5, 2013

Das Photo-Blue-Bottle Experiment wird hier in neuen Varianten, u.a. als Kompaktzelle ohne flüssige Komponenten designt. Das System verhält sich wie ein „Solar-Akku“.

Photokatalyse homogen und heterogen – das Photo-Blue-Bottle Experiment runderneuert, M. Heffen, M. W. Tausch, PdN-ChiS, Heft 6, 2015

Dieser Artikel enthält erstmalig Varianten des Photo-Blue-Bottle Experiments, die für Schulversuche entscheidend sind. Es werden Varianten des Experiments beschrieben, in denen das giftige Methylviologen durch harmloses Ethylviologen substituiert wurde, mit LED-Taschenlampen als Lichtquellen und in kleinen Schnappdeckelgläsern gearbeitet wird.

Photosynthese und Atmung en miniature, M. Heffen, M. W. Tausch, Chemie & Schule, 2016

In diesem Artikel wird eine Unterrichtsreihe beschrieben, in der die wesentlichen stofflichen und energetischen Grundlagen des Kreislaufs Photosynthese und Atmung für den Anfangsunterricht experimentell und konzeptionell aufbereitet wurden.

Metamorphosen eines Experiments – vom hightech UV-Tauchlampenreaktor zur lowcost Tic-Tac ® -Zelle, Y. Yurdanur, M. W. Tausch, CHEMKON, Heft 3, 2019

Die Retrospektive der wichtigsten Varianten des Photo-Blue-Bottle Experiments wird in diesem Artikel aufgezeigt und durch eine weitere Optimierung ergänzt. Die vorgeschlagene Photo-Blue-Bottle Konzentrationszelle als Kombination aus zwei Tic-Tac ® -Dosen kann von Schülern selbst hergestellt werden.

Unterwegs zur künstlichen Photosynthese – photokatalytische Reduktionen in Modellexperimenten, R. Kremer, M. W. Tausch, Chemie & Schule, 2019

Die Photo-Blue-Bottle Lösung wird in den neuen Varianten aus diesem Artikel genutzt, um in einer photogalvanischen Zweitopf-Zelle elementaren Wasserstoff zu erzeugen. Das ist ein Modell für die solargetriebene Herstellung eines „grünen“, klimaneutralen Treibstoffs ohne den Umweg über Photovoltaik und Elektrolyse.

Künstliche Photosynthese im Fokus – photokatalytische Wasserstofferzeugung in der Eintopfzelle, R. Kremer, C. Bohrmann-Linde, M. W. Tausch CHEMKON, 2021

Im Beitrag wird erstmalig über die photokatalytische Herstellung von Wasserstoff in einer LED-betriebenen Eintopfzelle berichtet. In einer 50-mL PBB-Zelle erhält man in 30 Minuten ca. 10 mL Wasserstoff. Dabei werden wesentliche Teilprozesse der künstlichen Photosynthese verwirklicht …

Nachhaltige Chemie mit Licht – Experimentelle Zugänge in digitalen Medien, C. Bohrmann-Linde, M. W. Tausch CHEMKON, 2021

Um die Entwicklung von nachhaltigen, auf Solarlicht basierenden Verfahren am Wissenschafts- und Technologiestandort Deutschland zu beschleunigen, muss Chemie mit Licht curricular vom Anfangsunterricht bis zum Abitur mit Experimenten, Konzepten und Lehr-/Lernmaterialien vertreten sein.

LED statt Gasbrenner - Mehr Licht für nachhaltigen Chemieunterricht , M. W. Tausch, Chemie in unserer Zeit, 2022

Die LED muss als Lichtquelle unter den Laborgeräten einen Stammplatz erhalten, ähnlich wie ihn als Wärmequelle der Gasbrenner hat. Der soll als Laborgerät nicht ersetzt, aber ergänzt werden, denn viele Reaktionen, bei denen der Gasbrenner chancenlos ist, können mit Licht aus LED oder mit Sonnenlicht bereits bei Raumtemperatur angetrieben werden. Es sind Reaktionen mit eminenter Bedeutung für die Nachhaltigkeit.

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