The effects of ionic strength on ions in aqueous solutions are quite relevant, especially for biochemical systems, in which proteins and amino acids are involved. The teaching of this topic and more specifically, the Debye-Huckel limiting law, is central in chemistry undergraduate courses. In this work, we present a description of an experimental procedure based on the color change of aqueous solutions of bromocresol green (BCG), driven by addition of electrolyte. The contribution of charge product (z(+)vertical bar z(-)vertical bar) to the Debye-Huckel limiting law is demonstrated when the effects of NaCl and Na2SO4 on the color of BCG solutions are compared.361187189