The coagulation values in millimoles per litre of the electrolytes used for the coagulation of $As_2S_3$ are given below : I. $(NaCl) = 52$, II. $(BaCl_2) = 0.69$, III. $(MgSO_4) = 0.22$ The correct order of the their coagulating power is
In pyrrole, the electron density is maximum on