High Quality Content by WIKIPEDIA articles! Perchloromethyl mercaptan,CCl3S, is mainly used as an intermediate for the synthesis of dyes and fungicides (captan, folpet). It is an oily, pale yellow liquid, which is insoluble in water, with a foul-smelling, unbearable, acrid odor. When it is heated or in a fire, it will emit toxic and corrosive gases. It is also very toxic by inhalation or skin absorption.