49. Solving a chemistry problem

The silver iodide sol was obtained by chemical condensation by the reaction of potassium iodide and silver nitrate in excess of the latter. Write the micelle formula, calculate the coagulation threshold, indicate the nature of the coagulating ion, if coagulation was observed by adding 0.5 ml of a 0.001 mol-eq./l solution of potassium iodide to 20 ml of the sol.