Figure 18. Use of flannel board with projector.
Figure 14. Demonstration of reaction in a fluid.
fluids or solutions, use a Petri dish as a receptacle. Place the dish
on the projection stage, and pour in the fluid or mix the desired solu-
tion. The projector now can be focused to show reactions at the bot-
tom of the dish, at the top of the dish, or at intermediate planes.