luminol experiment lab report

PhysicsOpenLab Modern DIY Physics Laboratory for Science Enthusiasts

Luminol and chemiluminescence.

February 6, 2019 English Posts , Light 28,013 Views

Chemiluminescence

Chemiluminescence  is the emission of electromagnetic radiation, particularly in the visible and near infrared, which can accompany a chemical reaction. Considering a reaction between the reagents A and B to give the product P:

A + B → P* → P +  hν

In practice, the reaction leads to the product P in an excited state and the decay to the ground state does not lead to the formation of heat, but of a photon ( hν ). It is therefore necessary that the mechanisms of radiative decay are more efficient than those that are not radiative.

An example of a reaction that leads to chemiluminescence is that of luminol with hydrogen peroxide catalyzed by metal ions.

Luminol  (C 8 H 7 N 3 O 2 ) is a chemical that exhibits chemiluminescence, with a blue glow, when mixed with an appropriate oxidizing agent. Luminol is a white-to-pale-yellow crystalline solid that is soluble in most polar organic solvents, but less soluble in water. Forensic investigators use luminol to detect trace amounts of blood at crime scenes, as it reacts with the iron in hemoglobin. Biologists use it in cellular assays to detect copper, iron, cyanides, as well as specific proteins.

To exhibit its luminescence, the luminol must be activated with an oxidant . Usually, a solution containing  hydrogen peroxide (H 2 O 2 ) and  hydroxide ions in water is the activator. In the presence of a catalyst such as an iron or periodate compound, the hydrogen peroxide decomposes to form oxygen and water :

2 H 2 O 2  → O 2  + 2 H 2 O

Laboratory settings often use  potassium ferricyanide  or potassium periodate for the catalyst. In the forensic detection of blood, the catalyst is the iron present in haemoglobin. Enzymes in a variety of biological systems may also catalyse the decomposition of hydrogen peroxide. Luminol reacts with the hydroxide ion, forming a dianion. The oxygen produced from the hydrogen peroxide then reacts with the luminol dianion. The product of this reaction — an unstable organic peroxide — is made by the loss of a nitrogen molecule, the change of electrons from triplet excited state to ground state, and the emission of energy as a photon. This emission produces the blue glow. The image below shows schematically the reaction that produces the luminescence:

We have prepared two solutions :

• Solution A Mix 5 grams of Sodium Hydroxide in 1000 ml of water. When thoroughly mixed & dissolved, pour some of this solution in a small (50 ml) beaker and add 0.1 grams of Luminol . Luminol is difficult to dissolve so to help, with a glass rod keep smashing the Luminol powder until it all goes into solution. When the Luminol is finally dissolved, pour the contents of the small beaker into the rest of the Sodium Hydroxide solution.
• Solution B Mix 10 ml of 3% Hydrogen Peroxide (regular drug store variety) in 1000 ml of water.

The image below shows the two solutions. The catalyst (Iron, Copper, …) is to be added to the solution B. Mixing the two solutions will produce the light emission from the chemiluminescence of the chemical reaction.

Experimental Setup

For the measurement of luminol chemiluminescence, we used the “dark box” already described in the posts: Photon Counting & Statistics , Glowing in the Dark . The solution “B” with the reaction catalyst is placed inside a glass bottle placed in front of the PMT. The solution with luminol is placed in a syringe outside of the box. After closing the box and starting the acquisition by the PMT, the luminol is introduced into the bottle with the syringe. The image below shows the experimental setup used:

Three different catalysts were used: potassium ferrocyanide (Fe ion), copper sulfate (Cu ion) and bleach (sodium hypochlorite).

Luminol Reaction with Iron Catalyst

The graphs below show the trend of the light emission catalyzed by the iron ion contained in the potassium ferrocyanide. After a first phase in which the emission increases and reaches a maximum, there is a decay with an exponential trend.

Luminol Reaction with Copper Catalyst

The graphs below show the trend of the light emission catalyzed by the copper ion contained in the copper sulphate. The brightness decay follows an exponential trend with two different time constants.

Luminol Reaction with Bleach Catalyst

The graphs below show the trend of light emission catalyzed by sodium hypochlorite. In this case, with respect to iron and copper, the increase in brightness is quite slow and the subsequent decay is exponential with two different time constants.

From the comparison between the three different curves we can say that the first part reflects the kinetics of the chemical reaction between the reactants: the reaction catalyzed by copper is faster than that catalyzed by iron while the reaction with sodium hypochlorite is the slowest one. The subsequent decay of luminescence generally follows an exponential trend (similar to the phenomenon of phosphorescence).

If you liked this post you can share it on the “social” Facebook , Twitter or LinkedIn with the buttons below. This way you can help us! Thank you !

If you like this site and if you want to contribute to the development of the activities you can make a donation, thank you !

Tags Luminol

Detection of beta and alfa radiation with KC761B

Abstract: in this article, we continue the presentation of the new KC761B device. In previous posts, we described the device in general terms and its functionality as a gamma spectrometer. In this post, we describe its use as a beta and alpha radiation detector. To detect beta and alpha particles, the device uses a PIN-type semiconductor sensor positioned on the back of the device.

• Social Sciences
• Natural Sciences
• Formal Sciences
• Professions
• Extracurricular

Luminol Synthesis and Chemiluminescence

Written by Lena

In this experiment, we synthesized luminol and used the product to observe how chemiluminescence works. Our starting material was 5-nitro-2,3-dihydrophthalazine-1,4-dione, which was, after addition of reaction agents, refluxed and vacuum filtered to retrieve luminol. Using two stock solutions, we missed our precipitated luminol with sodium hydroxide, potassium ferricyanide, and hydrogen peroxide, in their respective solutions, in a dark room, to observe the blue light emission.

INTRODUCTION

Anyone who has watched a CSI show on the television has probably seen the wonders of chemiluminescence. There is hardly an episode where we do not see one member of the CSI team spraying an unknown substance onto a surface, and using a black-light to show that all too familiar blue glow that indicates the presence of blood or body fluids. The unknown substance in the spray bottle is, in fact, luminol; and although its immediate effect is exaggerated on the television screen, it is effective and chemiluminescence does occur. Iron in hemoglobin serves as the ‘active ingredient’ in blood that causes the familiar glow.

In chemiluminescence, light is released without the heat from a chemical reaction; light is produced in this reaction through the energy released by the breaking, formation, or restructuring of chemical bonds. In a fluorescence reaction, the absorbance of light at a higher frequency, and consequent release at a lower frequency visible to the human eye, is the cause for the release of light.

The process of refluxing, which we use in this experiment, involves boiling a solution while continually condensing its vapor by cooling and returning the liquid to the reaction flask. Due to the fact that most organic reactions do not occur too quickly, chemists use this method to heat a reaction mixture for a long time without losing reagents. The reflux apparatus includes a jacketed condenser, where water flows into the bottom outlet and out of the top outlet. The apparatus is clamped to a stand, and a round-bottomed flask, or conical vial, containing a solution is attached before refluxing begins.

Also utilized in this experiment is the process of vacuum filtration, which is used for quick and complete separation of a solid from a liquid in a mixture. Filtration can be done using either a water aspirator line or a compressor-driven vacuum system. In this lab, we use a water aspirator line. In vacuum filtration, a Hirsch funnel, fitted with filter paper, is inserted into a filter flask which is attached to the vacuum trap. As mixture is poured into the funnel, the vacuum draws out liquid; and, leaving the aspirator running, the solid is allowed to dry.

Mohrig, J.R.; Hammond, C.N.; Schatz, P.F. Techniques in Organic Chemistry , 2010 , 59-60, 109.

EXPERIMENTAL PROCEDURE

To begin our experiment, we weighed out 5-nitro-2,3-dihydrophthalazine-1,4-dione (0.15g, 0.72 mmol), and added it to a 5mL conical vial with a spin vane. Into this same vial, we added sodium hydroxide (2mL, 3M), sodium hydrosulfite (0.25g, 1.4 mmol), and stirred. We washed solid residue from the sides of the conical vial using water (1mL). We then assembled the reflux apparatus using the jacketed condenser and water lines and attached the conical vial. This was followed by 5 minutes of reflux and stirring simultaneously, after which the solution was cooled to room temperature.

When the solution was sufficiently cooled, we added acetic acid (1mL, 17mmol, 1 equiv.) to the conical vial and stirred it for 5 minutes. The solution was then cooled on ice for 10 minutes. Using the vacuum filtration system, we filtered the precipitate and left it to dry with the aspirator running for 10 minutes. The precipitate recovered was luminol (0.24g, 1.4 mmol).

Moving on to the chemiluminescence experiment, we made four solutions: stock solution A, solution A, stock solution B, and solution B. Stock solution A was prepared using luminol (0.24g, 1.4 mmol) dissolved in sodium hydroxide solution (2mL, 3M) in a 25mL Erlenmeyer flask. Taking stock A (1mL) diluted in water (9mL) in a 50mL beaker, we made solution A. Stock solution B was prepared using potassium ferricyanide (4mL) and hydrogen peroxide solution (4mL) in a 25mL Erlenmeyer flask. Taking stock B (4mL), and diluting it with water (16mL), in a 50mL beaker, we got solution B. Finally, diluting solution A (3mL) with water (16mL) in a 150mL beaker, and pouring solution B (20mL) into this beaker, in a dark room, we were able to see the light emission as our solution turned blue.

RESULTS & DISCUSSION

The initial stirring of 5-nitro-2,3-dihydrophthalazine-1,4-dione (0.15g, 0.73 mmol), sodium hydrosulfite (0.25g, 1.4 mmol), and sodium hydroxide (2mL, 3M)  made a deep red/brown solution. After reflux and continuous stirring, a yellow coagulation/precipitate appeared on top of the solution. After the addition of acetic acid, yellow lumps of precipitate formed within the solution. Upon reflux and stirring of the solution, it turned orange and opaque, with visible floating flakes of precipitate. After cooling on ice and running through vacuum filtration, a mustard-colored, pasty luminol precipitate was recovered. For our experiment, we were able to recover 0.2436g (1.375 moles) of luminol. At first we thought the luminol would dry completely, but soon realized that it maintained a pasty consistency throughout the drying process. Stock solution A was a translucent red color, and stock solution B was a clear yellow, with frothy consistency on top. Our initial attempts at mixing the solutions say not emission light, for reasons we were unable to determine; but we mixed the solutions from stock again, and, fortunately, were able to see the blue luminescence in the beaker which lasted for about one minute, before fading away.

The experiments in today’s lab allowed us to see how luminol is instrumental in chemiluminescence. We see the outcome of chemiluminescence in contemporary media, but, in a laboratory setting, we are better able to be involved in the process. We can now understand that it is not blood itself, but the iron in its hemoglobin that causes this chemiluminescence. With this knowledge, we see the relevance of using potassium ferricyanide ( as a reactive agent. By investigating this multistep process, we have the opportunity to see the chemical roots of well-known phenomena.

Leave a reply Cancel reply

Your email address will not be published.

• For educators
• English (US)
• English (India)
• English (UK)
• Greek Alphabet

Your solution’s ready to go!

Our expert help has broken down your problem into an easy-to-learn solution you can count on.

Question: Synthesis of Luminol lab report NOTE: mechanism is not needed in this case DATA: 3-nitrophthalic acid used: 200 mg 8% aqueous hydrazine used: 0.4mL 3-nitrophthalhydrazide obtained: 130 mg sodium hydrosultafe dihydrate: 0.6 g luminol obtained: 70 mg NOTES: compute yield for nitrophthalhydrazide in the first step! (assume nitrophthalic acid is limiting

Synthesis of Luminol lab report

NOTE: mechanism is not needed in this case

3-nitrophthalic acid used: 200 mg

8% aqueous hydrazine used: 0.4mL

3-nitrophthalhydrazide obtained: 130 mg

sodium hydrosultafe dihydrate: 0.6 g

luminol obtained: 70 mg

compute yield for nitrophthalhydrazide in the first step! (assume nitrophthalic acid is limiting reagent)

compute yield for luminol in the second step! (using nitrophthalhydrazide as limiting reagent)

compute yield for the overall reaction! What conclusion can you draw about multi step reactions and yields?

the lab report need to have

ABSTRACT - Short summary of the experiment as a whole. It has to include 1-2 sentences of background theory, 1-2 sentences about what you did in the experiment, 1-2 sentences about the most important results and 1 sentence of conclusion.

OBSERVATION AND DATA (RESULTS) - Tabulate and organize the data obtained. This includes making graphs of the data and computations IF NEEDED!

REACTION MECHANISM - Proper arrow pushing formalism. Draw non bonding electron pairs, formal charges, and curved arrows which follow the electron flow.

DISCUSSION - 5-6 sentences. EXPLAIN the observations and data using the theory of the experiment. WHY did you get the data? Does the data obtained agree with the expectations? If not, why is it different? What are possible sources of error? A good rule of thumb is to have 1 sentence of explanation for each observation or data value you have. The individual assignments will have helpful questions showing you what to cover in your discussion.

This AI-generated tip is based on Chegg's full solution. Sign up to see more!

Calculate the number of moles of 3-nitrophthalic acid used by using its molar mass and the available mass of 200 mg.

Luminol synthesis is carried out by dehydration of 3-nitrophtha …

Not the question you’re looking for?

Post any question and get expert help quickly.

Your browser is not supported

Sorry but it looks as if your browser is out of date. To get the best experience using our site we recommend that you upgrade or switch browsers.

Find a solution

• Skip to main content
• Skip to navigation

• Back to parent navigation item
• Collections
• Sustainability in chemistry
• Simple rules
• Teacher well-being hub
• Women in chemistry
• Global science
• Escape room activities
• Decolonising chemistry teaching
• Teaching science skills
• Get the print issue
• RSC Education

• More navigation items

Chemiluminescence - the oxidation of luminol

By Adrian Guy 2010-03-01T00:00:00+00:00

Light without heat

Chemiluminescence is a 'fascinating phenomenon where a chemical reaction produces light without heat'. The oxidation of luminol is a good example.

The oxidation of luminol

Dissolving luminol (3-aminophthalhydrazide or 5-amino-2,3-dihydro-1,4-phthalazinedione) in a base abstracts the protons from the two cyclic nitrogen atoms, resulting in a intermediate which is readily oxidised by hydrogen peroxide or household bleach (sodium chlorate(I)) to an excited intermediate, the decay of which to a lower energy level is responsible for the emission of a photon of light.

Having experimented with several different methods from a variety of sources to demonstrate chemiluminescence, often with disappointing results, I found the following method, by Declan Fleming of the University of Bristol, to work effectively in a blacked out classroom setting. This method results in a relatively rapid rate of reaction, producing bright chemiluminescence albeit on a short timescale.  

Down the tube

I use a colourless, spiral, plastic tube to highlight the 'glow', but other methods of mixing the two solutions - basic luminol and dilute hydrogen peroxide - in approximately equal proportions, can be equally impressive. As an alternative, for example, soak a rag in one solution and dip it into the other solution - the rag glows as you wring it out.  

Source: © georgina batting

• 4 g of sodium carbonate
• 0.2g of luminol (irritant)
• 24g of sodium hydrogencarbonate
• 0.5g of ammonium carbonate
• 0.4g of copper sulfate
• 50ml of 30 vol hydrogen peroxide
• deionised water
• two one-litre flasks
• flexible, colourless, plastic tubing 
• retort stand and several clamps
• filter funnel to fit into rubber tubing
• fluorescein

Procedure 

To 1 dm 3 of deionised water add the sodium carbonate, sodium hydrogencarbonate, ammonium carbonate, copper sulfate and luminol. Swirl to dissolve. In a separate flask add 50 ml of 30 vol hydrogen peroxide solution and make up to 1 dm 3 .

The two solutions, when mixed in approximately equal amounts will react to oxidise the luminol, producing the characteristic blue glow. If you add a small quantity of fluorescein to the copper sulfate solution you will get a green glow. 

To produce an effect as shown in the photograph construct a spiral of colourless, plastic tubing with a funnel in the top and a waste collection vessel (beaker) at the bottom, and then pour the two solutions into the spiral at the same time.

Special tips

This demonstration can only be appreciated in a dark room, so black out blinds are invaluable. The solutions do not keep well and should be made on the same day of use. Old luminol is unreliable, but fresh yellow/grey luminol works well

Teaching goals

Demonstrating rates of reactions is easily done in the classroom, but too often teachers resort to using the reaction between marble chips and hydrochloric acid. The oxidation of luminol makes for a welcome change as a demonstration, or for a class-based investigation. The effects of temperature, concentration and catalysts all have a profound effect on the rate, and thus the intensity of the light produced.  

Try mixing smaller quantities of the two solutions in 50 ml beakers at different temperatures, or altering the concentration of the hydrogen peroxide solution and note the effect. Use different transition metal ions to catalyse the reaction, or none, and observe the effect - judge the light intensity and thus the rate by eye.  

Hydrogen peroxide solution (30 vol) is unstable and readily decomposes to water and oxygen, which would increase the pressure inside the bottle - take care when opening. Hydrogen peroxide forms potentially explosive compounds. Materials to avoid include combustibles, strong reducing agents, most common metals, organic materials, metallic salts, alkalis, porous materials, especially wood, asbestos, soil, rust, and strong oxidising agents. Goggles and (disposable) nitrile gloves are essential when handling the H 2 O 2 solution.

Luminol is an irritant.

Once made up, the diluted hydrogen peroxide solution is an irritant (skin, eyes and lungs) and the alkaline luminol solution is low hazard.

Sodium carbonate is an irritant (skin), and ammonium carbonate and copper sulfate are irritants and harmful if ingested. 

This article was updated on 11 December 2023. If you're thinking about doing this experiment, you could also consider the  Chemiluninescence of luminol: a cold light experiment .

• Organic chemistry
• Rates of reaction
• Reactions and synthesis

Related articles

Magical demonstrations

2016-12-22T10:25:00Z By Neil Monteiro

Neil Monteiro shows how taking lessons from magicians can make your demos come alive

Luminol fountain

2013-03-01T00:00:00Z By Declan Fleming

Create a dramatic and eerie 'cold light' fountain

Could Titan’s hydrocarbon seas support life?

2024-09-13T07:44:00Z By Nina Notman

Probing the seas of Saturn’s largest moon

1 Reader's comment

Only registered users can comment on this article., more exhibition chemistry.

Dissolve coloured sweets to create a rainbow

2024-10-21T05:02:00Z By Declan Fleming

Demonstrate diffusion, density and the particle model to your 14–16 learners in this easy experiment

Demonstrations with dry ice

2024-08-27T06:00:00Z By Declan Fleming

Explore changes of state and neutralisation reactions with this trio of demonstrations using solid carbon dioxide 

Non-burning paper: investigate the fire triangle and conditions for combustion

2024-06-10T05:00:00Z By Declan Fleming

Use this reworking of the classic non-burning £5 note demonstration to explore combustion with learners aged 11–16 years

• Contributors
• Print issue
• Email alerts

Site powered by Webvision Cloud