Lesson 17:

Liquid Light

Concepts conveyed | Materials | Procedure | Benefits | Resource

Concepts conveyed:

The purpose of this demonstration is to show an example of how energy generated in a chemical reaction can be given off as light instead of heat.

Materials:

• 0.4 g luminol (3-aminophthalhydrazide)
• 1.0 g NaOH
• water (~2 L)
• 40 mL of 3% hydrogen peroxide
• 1.0 g potassium ferricyanide
• funnel with long glass tube (or a spiral condenser)
• 2, 1 L beakers or flasks
• 1, 2 L beaker or flask
• clamp (to attach the funnel to the edge of a table)

Procedure:

Prepare the luminol-containing solution fresh. Mix solution “A” (luminol, NaOH, and water to one liter) in a one liter beaker or flask. Mix solution “B” (hydrogen peroxide, potassium ferricyanide, and water to one liter) in the other one liter beaker or flask. Support the funnel (with the long glass tube) over the edge of a table with a clamp. Place a two liter beaker or flask at the end of the glass tube. Dim the lights in the classroom and pour the two solutions, A and B, together into the funnel. As they mix and react, blue light is given off. In a darkened room, the column of light that passes down the glass tube can be impressive.

A long spiral condenser can substitute for the straight glass tube, and is more dramatic when the glowing solution runs through it.

Benefits:

• This demonstration is a unique way to demonstrate that, among other topics, chemistry also involves light. The chemicals combine in such a way as to produce energy in the form of light.

Resource:

• Chemistry for Museums: A Manual of Chemistry Demonstrations; Center of Science and Industry: Columbus, OH, 1976; Show #4, Demonstration #5; Project Funded by a National Science Foundation Grant #7423549.