ABSTRACT
A round-bottomed flask is filled with water and used to focus a spot of light from an arc on to a piece of black card. Because the water absorbs the heat radiation there is no effect on the card.
An identical flask filled with carbon tetrachloride in which iodine has been dissolved to make it completely opaque to visible light is then substituted for the water-filled flask. The black card begins to burn as a result of the focused heat radiation for which the iodine solution is transparent. The effect can be made even more dramatic if a little gunpowder or other very inflam mable material is attached to the card.
