Abstract: Luminol demonstrates chemiluminescence which is when there
is physical glow to a solution when there is a catalyst. Forensic investigators use luminol to
detect trace amounts of blood at crime scenes, as it reacts with the iron in hemoglobin.
Biologists use it to detect copper, iron, and cyanides. When the luminol used
at a crime scene its catalyst is the iron in the blood. Luminol is made up of
carbon, hydrogen, nitrogen, and oxygen. The physical appearance of luminol is a
whitish to yellow color. Luminol is a solid and is soluble in most polar
organic solvents, but insoluble in water.
in an alkaline solution of hydrogen peroxide was
discovered in 1928 by a German chemist H. O. Albrecht. Later in 1937 a German
forensic scientist Walter Specht made extensive research in a criminal
investigation where blood was present. This experiment worked and detected
blood. Something that was discovered is the longer the blood decomposed and
dried gave a longer more lasting reaction than fresh blood. Luminol when
sprayed on the area that is thought the glow will last for a few seconds.
Luminol is used
usually in forensics to detect blood that has come into contact with surfaces.
Iron works as a catalyst because iron is found in blood. Apart from iron there
are many other catalyst to make the luminol have the chemiluminscence
Some of those
reactants are bleach, some copper compounds, fecal matter and even horseradish.
As seen in this picture many things can be a catalyst to cause the glow. Many
people believe the luminol has a long lasting reaction as seen on TV in the
forensic shows, but when luminol is reacted with the catalyst in real life the
reaction most of the time lasts few seconds.
Reason behind the Reaction
luminol is an organic compound that when it is oxidized it will emit light.
Which is known as chemiluminescence. The reason of the glow has to do
with the energy levels. What happens in the energy levels is energy is then
released in the form of a
photon of light from each molecule as it drops back to
a stable lower energy state. In this
photo it shows the luminol structure at it original state and what
happens after you add the catalyst. In this case when you add the hydrogen
peroxide. After the hydrogen is added to the luminol mixture a photon is
produced. A photon is particle representing a quantum of a light; therefore
creating the chemiluminsecence.
experiment to show the catalyst that will cause the chemiluminsecence in the
luminiol instead of using iron as a cause of reactant, I will be using diluted
The reaction will last a few
seconds. Although it will be visible to the naked eye.
Material & Methods
experiment you will be making a solution of luminol to be reacted with diluted
bleach. Bleach will act as the catalyst in this experiment. First thing to do
is gather the materials for the luminol solution. You will need powder luminol,
NaOH, and distilled H2O. Fill a 250mL of distilled H2O
into a 500mL Erlenmeyer flask. Grab a small 30mL medicine cup and zero out the
weight on scale measured in grams to the second decimal place. Take the powder
luminol measure out .12g of luminol in the medicine cup. Pour the .12g of
luminol into the 250mL of water. Take another 30mL medicine cup and zero then
weigh 1g of NaOH. Pour the 1gram of NaOH into the water with the luminol. Wait
minute until it is completely dissolved. The physical appearance of the luminol
solution is a light yellow. Next thing to do is making the simple bleach
solution. You first need to take the household bleach and measure 5mL in the
medicine cup. Fill 250mL of H2O in an Erlenmeyer flask. Pour in the
5mL of household bleach into the water. Stir the water and bleach together.
parts of luminol solution and diluted bleach. Take a250mL Erlenmeyer flask and
pour in the two equal parts into the Erlenmeyer flask. Observe the reaction
that that occurs and record in in the data table given.
H2O (combined w/ luminol sol.)
H2O (use to dilute bleach)
I conducted the lab what I observed is that when I combined equal parts of the
luminol and the diluted bleach at the same time into the 250mL Erlenmeyer flask
the blue glow was visible for a few seconds and slowly faded away. The bleach
definitely worked as a catalyst. I realize also that amount what you combine
the luminol and diluted bleach matter. You need to make sure that is equal
parts or the maximum of
time it will glow will be decreased.
Luminol is used by forensics to detect
the iron in blood when it has been wiped up. In this experiment my job was to
prove this statement by conducting many experiments. I used household bleach as
a catalyst because the lumniol does have many catalyst. In conclusion I proved
this to be true. In my data looking at the measurements the amounts I used
worked perfectly to reach the amount of glow to be visible to prove my
statement to be true. Using equal amounts is crucial when pouring them
together. I had many trial when trying to figure out which lab experiment would
be the best. I found that if the bleach was not diluted enough with water a
second reaction that can happen is a chemical reaction. It would bubble and then
turn a dark orange and brown. Also by adding hydrogen peroxide with bleach
there would also be the same chemical reaction of bubbling. When presenting my
lab I will be either be using this experiment that contains the bleach and
luminol solution combined or I will be using the Blue Star tablet of lumniol
which is probably used in a real forensic case. The major finding in the
luminol chemilumscence is that iron in blood is not the only that can cause a
reaction with lumniol and that measurements are very important.