49. Solving a chemistry problem

The lead sulfide sol was obtained by chemical condensation with an excess of sodium sulfide. Write the formula for a micelle. With the destruction of this sol, a clear condensation was observed when 0.5 ml of a magnesium chloride solution with a concentration of 0.0001 mol-eq./L was added to 15 ml of the sol. Determine which ion is coagulating? Calculate the coagulation threshold.