The equilibrium between chromate(VI) and dichromate(VI) ions is another good example that can be used to illustrate the effect of change of concentration on equilibrium position. There is a clear difference in colour between solutions of the two ions so that shifts towards reactants or products can be clearly seen. The experiment can be used by students working in small groups on a test tube scale or by adding drops of solution onto an acetate sheet on a microscale. It could also be demonstrated by the teacher using larger amounts of materials.