In the coagulation of arsenlous sulphide, `Al(NO_(3))_(3)` is a better coagulating agent than `KNO_(3)`. Explain.

Explanation

Arsenious sulphide `(As_(2)S_(3))` is a lyophobic sol. Its colloidal particles are negatively charged and can be neutralised by positively charged ions (here, `Al^(3+) & K^(+)`). As the charge of `A1^(3+)` is higher than that of `K^(+) ,A1(NO_(3))_(3)` is more effective in coagulation of `As_(2)S_(3)` sol than `KNO_(3)`