In a number of previous papers a mathematical study was made of small drops, which either absorb or produce some substances by virtue of physico‐chemical reactions. This creates in the drop and in the surrounding medium gradients of concentrations of corresponding substances. In this note it is pointed out that when the reacting substances are ionized, these gradients will result in the appearance of electric charges and electric fields. An estimation shows that they are quite comparable with electric charges, produced by other factors in disperse systems. The fundamental property of the charges here considered is that they disappear as soon as the reactions cease. Their importance in biological systems is pointed out.