Platinised asbestos helps in the formation of SO_(3) from SO_(2) and O_(2). But, if even a small amount of As_(2)O_(3) is present the platinised asbestos does not help in the formation of SO_(3). As_(2)O_(3) acts here as

Platinised asbestos helps in the formation of SO_(3) from SO_(2) and O

1.	Platinised asbestos helps in the formation of SO_(3) from SO_(2) and O_(2). But, if even a small amount of As_(2)O_(3) is present the platinised asbestos does not help in the formation of SO_(3). As_(2)O_(3) acts here as
Answer» A POSITIVE catalyst A negative catalyst An autocatalyst A POISON Solution :`2SO_(2)+O_(2)underset(As_(2)S_(3)("Poison"))overset("Platinised asbestos (catalyst)")to2SO_(3)`.