As part of your lab work and criminal investigation, there will be several times where you will need to create solutions or weigh out the appropriate amount of a substance based on its molarity or molar amount. You now have the tools to do this.
For the example use in this lecture we are going to focus on the chemical Luminol.
Chemiluminescence of Luminol
mabakken (YouTube)
Luminol is a chemical that undergoes a reaction with oxygen when in the presence of a catalyst (Gary, please attach a pop up definition to the word catalyst (a substance that causes or accelerates a chemical reaction without itself being affected.)) that produces a bright blue glow. Luminol is used in forensic analysis for the detection of blood on surfaces like wood, carpet etc. The iron (Fe) in hemoglobin, a chemical found in blood, acts as the catalyst that causes the solution to glow.
There are other catalysts that can cause a similar reaction, copper and cyanide for example, so the use of luminol at a crime scene must be controlled so that a false indications is not made. In simple terms, you cannot use the solution to detect blood on a copper pot. In the laboratory we often use potassium ferricyanide, K3[Fe(CN)6] as the catalyst.
Using the test in the field, luminol powder (C8H7O3N3) is mixed with hydrogen peroxide (H2O2) and a hydroxide (e.g., NaOH) in a spray bottle. The luminol solution is sprayed where blood might be found. The iron from the hemoglobin in the blood serves as a catalyst for the chemiluminescence reaction that causes luminol to glow, so a blue glow is produced when the solution is sprayed where there is blood. Only a tiny amount of iron is required to catalyze the reaction. The blue glow lasts for about 30 seconds before it fades, which is enough time to take photographs of the areas so they can be investigated more thoroughly.